WO2004106343A2 - Agelastatin derivatives of antitumour and gsk-3beta-inhibiting alkaloids - Google Patents

Abstract

A compound of general structure (I); or, a pharmaceutically acceptable salt thereof, wherein, Formula (A) and Formula (B) = independently a single or a double bond; A = C, N, O, S, or Se; Z = C, N, 0, S, or Se; R1, R2, R3, R7 and R8 are independently selected from H, CI-10 alkyl, Cl-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR9, SR9, OH, N02 CN, NH2, NHR9, N(R9)2, NHOR9, NHCONHR9, NHCONR92, NR9COR9, NHC02R9, C02R9, C02H, COR9, CONHR9, CON(R9)2, S(O)2R9, S(O)R9, SONH2 SO2NHR9, NHS(O)2R9, and Si(R9)3 groups, or an optionally substituted heterocyclic group; and R9 = H, Cl-10 alkyl, Cl-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl.

Description

MOLECULES AND ANALOGUES OF THE AGELASTATIN FAMILY OF ANTITUMOUR AND GSK-3 β-rNHIBITING ALKALOIDS

The present invention relates to alkaloids of the agelastatin family, in particular (-)-agelastatins A and B, and an enantiospecifϊc process for their preparation.

(-)-Agelastatin A (-)- Agelastatin B (-)-Agelastatin D

The agelastatins are a structurally novel family of Oroidin alkaloids, obtained from marine sponges, that have powerful antitumour and insecticidal properties, both in vitro and in vivo (D'Ambrosio, M. et. al., J Chem. Soc. Chem. Comm. 1993, 135; Helv. Chim. Ada, 1994, 77, 1895; Helv. Chim. Acta. 1996, 79, 727). ' (-)-Agelastatin A is also a potent and highly specific inhibitor of glycogen synthase kinase 3-β (GSK-3-β)

(Meijer, L. et al, Chem. & Biol, 2000, 7, 51).² Upregulated GSK-3β activity is associated with the hyperphosphorylation of tau, a microtubule-binding protein that forms neurofibrillary tangles when it becomes hyperphosphorylated (S. Lovestone et al, Curr. Biol, 1994, 4, 1077; A.J. Harwood, Cell, 2001, 105, 821). As these tangles are present in the brain tissues of patients with Alzheimer's disease (AD), and absent from the brains of normal subjects, it is widely believed that selective inhibitors of GSK-3 β activity could prove useful for treating neurodegenerative disorders such as AD. GSK-3- β inhibitors could also function as novel insulin-mimetics, for insulin activates a cell- signalling pathway (the protein kinase B cascade) that inhibits GSK-3 β (Eldar- Finkelman, H. Trends Mol Med., 2002, 8, 126). Inhibitors of upregulated GSK-3 -β activity might additionally act as neuroprotective agents preventing neuronal apoptosis after stroke (Martinez, A. et al, Medicinal Res. Rev., 2002, 22, 373).

As such, molecules and analogues of the agelastatin family might have useful pharmacological properties, such as anticancer, anti-diabetic, anti-stroke, anti- inflammatory, immunosuppresant or anti-AD activity, and represent effective treatments for these diseases. They might also even serve as environmentally benign insecticides. New and readily modifiable synthetic pathways to these molecules are therefore of great interest and potential importance.

The first total synthesis of an agelastatin family member was achieved in 1999 by Weinreb and coworkers (Stein, D., et. al, J. Am. Chem. Soc. 1999, 121, 9574; J Org. Chem., 1998, 63, 7594), with their report of the synthesis of (+)-agelastatin A. The first asymmetric synthesis of (-)-agelastatin A was accomplished in 2002 by Feldman and Saunders (Feldman, K.S., J Am. Chem. Soc, 2002, 124, 9060; J. Org. Chem., 2002, 67, 7096); this also provided the sister compound, (-)-agelastatin B. An asymmetric pathway to the (-)-agelastatin skeleton has additionally been described by O'Brien's group at the University of York (Baron, E., Tetrahedron Lett., 2002, 43, 723), but this strategy has not, so far, been developed into a full total synthesis of a naturally-occurring agelastatin family member.

The exceedingly novel structures of the agelastatins, combined with their powerful antitumour effects against KB and L1210 tumour cell lines, make them of considerable interest as future, potential, antitumour drugs. Indeed, (-)-agelastatin A was reported to inhibit a human KB nasopharyngeal cancer cell line at the very low drug concentration of 0.075 μg/mL (this was its IC₅₀). It was also found to prolong the life expectancy of mice with L1210 murine leukaemia when repeatedly administered intraperitoneally at doses of 2.6 mg/kg, although no antitumour effects were noted when it was given intravenously. The antitumour mechanism of (-)-agelastatin A has yet to be elucidated. Therefore, it is an object of the present invention to provide an enantiospecifϊc synthesis for compounds of the agelastatin family and in particular (-)-agelastatin A. Furthermore, it is desirable that the synthetic route developed can be readily modified to produce novel agelastatin analogue structures having potentially useful pharmacological properties such as anticancer, anti-diabetic, anti-inflammatory and anti-AD activity or the ability to reduce tissue damage after stroke.

According to the first aspect of the present invention there is provided a compound of general structure I

General Structure I

or a pharmaceutically acceptable salt thereof, wherein, C— A and Z— C = independently a single or a double bond;

A = C, N, O, S, or Se;

Z = C, N, O, S, or Se;

R¹, R ², R³, R⁷ and R⁸ are independently selected from H, C_1-10 alkyl, C_J._IO cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR⁹, SR⁹, OH, NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂, NR⁹COR⁹,

NHCO₂R⁹, CO₂R⁹, CO₂H, COR⁹, CONHR⁹, CONR⁹ ₂, S(O)₂R⁹, S(O)R⁹, SONH₂,

SO₂NHR⁹, NHS(O)₂R⁹, and Si(R⁹)₃ groups, or an optionally substituted heterocyclic group;

R⁹ = H, C_LIO alkyl, C_LIO cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl; According to a second aspect of the present invention there is provided a compound of general structure II

General Structure II

or a pharmaceutically acceptable salt thereof, wherein,

C— A, X— Y, Y— Z, and Z— C = independently a single or a double bond; A, X, Y and Z = independently selected from C, N, O, S, or Se;

R¹, R², R³, R ⁴, R⁵, R⁶, R⁷ and R⁸ are independently selected from H, C_1-10 alkyl, C_1-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl,

OR⁹, SR⁹, OH, NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂,

NR⁹COR⁹, NHCO₂R⁹, CO₂R⁹, CO₂H, COR, CONHR, CONR⁹ ₂, S(O)₂R⁹, S(O)R⁹, SONH , SO₂NHR⁹, NHS(O)₂R⁹, and Si(R⁹)₃ groups, or an optionally substituted heterocyclic group or R³ and R ⁴, R⁵ and R⁶, and R⁷ and R⁸ are taken together and selected from =O, =C(R⁹)₂, =S, =NR⁹, =Se;

R⁹ = H, C_LIO alkyl, C_LIO cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl; n is any number of atoms that will produce a partially unsaturated or fully saturated 3 to 8 membered ring system containing 0 to 3 heteroatoms.

The combinations of chemical functionality allowed in the compounds of the second and third aspects of the present invention are constrained only by normal chemical valency and bonding rules with regard to the atoms involved which in turn dictate whether substituents R¹ to R⁹ are absent or present. These rules are well known to those skilled in the art. In both general structures I and II where C^~ A and Z— C are single bonds the valency requirements of the carbon atom are preferably fulfilled by way of a hydrogen atom.

In General Structure I it is preferred that when Z is S, R⁷ be taken as either a single =O or as a pair of =O groups, and R be alkyl, cycloalkyl, aryl, or heteroaryl grouping.

The compounds of the present invention may be obtained as a salt, preferably as a pharmaceutically acceptable salt of General Structure I and or General Structure II.

Examples of such salts include, but are not limited to, those derived from organic acids such as acetic acid, malic acid, tartaric acid, citric acid, lactic acid, succinic acid, fumaric acid, maleic acid, oxalic acid, benzoic acid, salicylic acid, phenylacetic acid, mandelic acid, methanesulfonic acid, benzenesulphonic acid and 7-toluenesulfonic acid, mineral acids such as hydrochloride and sulfuric acid and the like. Examples of suitable inorganic bases for the formation of salts of compounds of the present invention include the hydroxides, bicarbonates, carbonates and alkoxides of ammonia, lithium, sodium, potassium, calcium, aluminium, iron, magnesium, zinc, and the like. Salts can also be formed with suitable non-toxic organic bases such as arginine and lysine but may include mono-, di-, trihydroxyalkylamines, and mono-, di- and trialkylamines, and the like.

Salts may be prepared in a conventional manner by methods well-known in the art. The compounds of this invention may also exist in solvated or hydrated or polymorphic forms.

A further aspect of the present invention provides a process for the enantiospecific synthesis of (-)-agelastatin A from D-glucosamine hydrochloride, wherein said process involves the enantiospecific synthesis of Boc-cyclopentene oxazolidinone (see compound 17 of scheme 1) Advantageously, the process of the present invention provides an enantiospecific synthetic route to a very useful compound. Furthermore, the synthetic route can be readily modified in order to prepare compounds analogous to (-)-agelastatin A.

The present invention includes the intermediates shown in Scheme 1 and methods for their synthesis.

All the compounds shown in scheme 1 are optically active with the exception of compound 24.

III

In the process outlined above, the advanced intermediate III is prepared in enantiomerically pure form from D-glucosamine hydrochloride. Weinreb and co-workers previously converted racemic III into (+)-agelastatin A by a two step, one-pot, protocol that involved successive treatment of III with iodotrimethylsilane followed by methyl isocyanate and base (Stein, D., et. al, loc. ci ).

The synthesis of (-)-26, and thereafter the synthesis of (-)-agelastatin A, begins with the preparation of aziridine 2.

The latter is an extremely useful chiral building block that is cheap and readily prepared on large scale by the procedure of Hough and Richardson (Buss, D. H. et al, J. Chem. Soc. 1963, 5295; Buss, D. H. et. al, J. Chem. Soc, 1965, 2736; Gibbs, C. F. et. al, Carbohydrate Res., 1965, 1, 290; Ali, Y. et. al, Carbohydrate Res. 1984,129, 267). Importantly, their five-step protocol does not involve any chromatography; all the intermediates being highly crystalline and readily purified by recrystallisation. The N- acyl derivatives of 2 show a marked preference (Buss, D.H.; Hough, L.; Richardson, A.C., J Chem. Soc, 1965, 2736; Guthrie, R.D.; Murphy, D. J. Chem. Soc. 1965, 3828; Hough, L.; Penglis, A.A.E.; Richardson, A.C. Carbohydrate Res., 1980, 83, 142; Gurjar, M.K.; Patil, V.J.; Yadav, J.S.; Rama Rao, AN. Carbohydrate Res. 1984, 129, 267; Charon, D.; Mondage, M.; Pons, J-F.; Le Bray, K.; Chaby, R. Biorg. Med. Chem. 1998, 6, 755) for undergoing trαns-diaxial ring-opening reactions with a variety of strong nucleophiles to give 3-amino-sugars with the α-D-α/trø-configuration. As a consequence, it was predicted that when the N-methylcarbamate derivative 3 was reacted with sodium azide in hot DMF, it would afford 4 as the major reaction product.

₀Me

In the event, a very smooth and highly regioselective aziridine ring-opening proceeds at 140°C with just 4 equiv of NaN₃, the desired azide 4 being produced as the sole reaction product in 88% yield. The azido group of 4 may be readily hydrogenolysed in the presence of a suitable catalyst such as Pearlman's catalyst to give the amine 5 which, without any further purification, is protected with a protecting group such SESC1 (Huang, J.; Widlanski, T.S. Tetrahedron Lett. 1992, 33, 2657. Other protocols for SESC1 preparation include; Weinreb, S.M.; Demko, D.M.; Lessen, T.A.; Demers, J.P. Tetrahedron Lett. 1986, 27, 2099 and Weinreb, S.M.; Chase, C.E.; Wipf, P. Venkatraman, Org. Synth., 1997, 75, 161);

the combined sequence provides 6 in 61% overall yield.

The O-benzylidene acetal of 6 is next detached by hydrolysis with, for example anhydrous methanolic HC1 to give 7.

7 is then selectively converted in order to provide a reactive substrate for nucleophilic substitution. Preferably, this is achieved by O-tosylation of the primary alcohol in 79% yield with tosyl chloride, DMAP, and Et₃N in CH₂C1₂ to provide 8.

8

O-Silylation of 8 with triethylsilyl chloride and DMAP in pyridine subsequently provides 9.

The latter is converted into iodide 10 by nucleophilic displacement with, for example, Nal in acetone at reflux.

10

10 may then be converted to 11 by way of a Vasella reductive ring-opening (Bernet, B. et. al. Helv. Chim. Ada., 1976, 62, 1990; Bernet, B. et. al, Helv. Chim. Ada., 1976, 62, 2400) with zinc dust in aqueous THF.

11 Aldehyde 11 may then be methylenated by way of Kocienski's modification (Blakemore, P. R. et. al. Synlett, 1998, 26; Blakemore, P.R. et. al, J. Chem. Soc. Perkin Trans. 1, 1999, 955) of the Julia reaction (Baudin, J. B. Tetrahedron Lett. 1991, 32, 1175) with the anion derived from sulfone 12.

The recently developed Hoveyda-Grubbs ruthenium alkylidene 14 (Kingsbury, J.S.; Harrity, J.P.A.; Bonitatebus, Jr., P.J.; Hoveyda, A.S. J. Am. Chem. Soc. 1999, 121, 791; S.B. Garber; Kingsbury, J.S.; Gray, B.L.; Hoveyda, A.M. J. Am. Chem. Soc 2000, 122, 8168) is by far the most effective and convenient catalyst currently available for effecting the ring-closing metathesis reaction of diene 13 to obtain cyclopentene 15.

13 15

The use of catalyst 14 furnishes 15 in 41% overall yield for 3 steps; notwithstanding the presence of potentially troublesome urethane and sulfonamido NH groupings, which often deactivate the Grubb's RCM catalysts (for some leading reviews on RCM that discuss Ru alkylidenes in great detail, see: Grubbs, R.H.; Miller S.J.; Fu, G.C. Ace. Chem. Res., 1995, 28, 446; Grubbs, R.H.; Chang, S. Tetrahedron, 1998, 54, 4413; Furstner, A. Angew. Chem. Int. Ed. 2000, 39, 3012) of earlier vintage.

Advantageously, the use of alkylidene 14 leads to higher yields of product 15 than its predecessor catalyst 27 (which is also effective for this RCM reaction); 14 is also much faster at converting 13 into 15. The original Grubbs RCM catalyst 28 performs poorly in this ring-closure.

14

The O-desilylation of 15 may be effected by a fluoride ion source such as TBAF.

However, the use of TBAF is problematical. The TES group can be cleaved in 56-76% yield using an organic acid such as aqueous acetic acid in THF at room temperature (RT).

The latter may then be converted to the oxazolidinone 16 by K₂CO₃ treatment in MeOH.

However, it is generally superior to obtain oxazolidinone 16 directly from 15 by heating 15 with a abse such as K₂CO₃ in a solvent such as MeOH at reflux for 2 h.

ES 16

Compound 16 may then be N-acylated using an acylating agent such as Boc₂O with a catalyst such as DMAP in CH₂C1₂ to provide (-)-17. The use of Boc₂O, DMAP and CH₂C1₂ provides 17 in 62% yield.

Oxazolidinone 17 is an advanced intermediate in Weinreb's racemic total synthesis of agelastatin A. However, unlike Weinreb's route, the route described herein delivers (-)-17 in enantiomerically pure form for the very first time. The structure and absolute stereochemistry of (-)-17 was proven by single-crystal X-ray analysis (this was performed by Dr Derek Tocher of the Chemistry Department, University College London).

A number of important process improvements and modifications have been made to Weinreb's synthesis for racemic agelastatin A in order to provide a synthesis for enantiomerically pure natural product.

17 is converted to 19 by way of Weinreb's N-acylation with acid chloride 18 in an 80% yield.

19

The SES group of 19 can be cleaved using TBAF, as reported by Weinreb, such cleavage was found to be problematical, typically proceeding in only a 33% yield compared to a reported yield of 66%. Therefore, alternative procedures have been developed. The SES group of 19 may be cleaved using an fluoride ion source such as CsF in DMF at RT for 19 hours, prior to heating it at 50°C for 1 hour. The use of CsF furnishes the desired product (-)-20 in a yield of 46-68%.

The selective hydrolysis of the oxazolidinone in 20 may be carried out in accordance with Weinreb's procedure which employs LiOH in THF. An alternative procedure which yields similar results employs a base such as Cs₂CO₃ in a solvent such as MeOH. The selective hydrolysis provides a 7:3 mixture of products 22:21. Due to the difficulties of separating 22 from 21 by SiO₂ flash chromatography a chromatographed (but not separated) mixture of 22 and 21 is oxidized using, for example, TPAP and NMO to obtain a mixture of 23 and 21. Weinreb carried this oxidation step using the CrO /Py protocol well known to those skilled in the art.

21 22

Advantageously, the TPAP oxidation is much easier to work-up than the CrO₃/Py protocol, and uses only catalytic quantities of the transition metal oxidant, which is preferable for large scale industrial work.

As the separation of 23 from 21 by SiO₂ column chromatography remains very difficult the cyclisation of 23 to 25 is therefore accomplished by exposing the mixture of 23 and 21 to a base such as Cs₂CO₃ in a solvent such as MeOH, under conditions similar to those originally reported by Weinreb, but involving substantially less Cs₂CO₃.

23 When the reaction is complete, TLC analysis of the crude reaction mixture invariably indicates the presence of three main reaction components: 24, (-)-25, and (-)-21. Compounds 24, (-)-25, and (-)-21 are now readily separated by SiO₂ flash chromatography; the desired product (-)-25 is generally isolated in 18% overall yield for the three steps from (-)-20.

Surprisingly, Weinreb and coworkers did not report the formation of 24 in their cyclisation reaction, yet it has been found that this undesired by-product is always produced in around 7% overall yield from (-)-20. One possible mechanism that accounts for the formation of 24 is shown in Scheme 3; it invokes γ-deprotonation occurring in (-)- 23 to generate a cyclopentadienol or a caesium cyclopentadienolate (for deliberate generation of a 6-π aromatic cyclopentadienolate dianion from a cyclopentenone, see Koreeda's total synthesis of (+)-coriolin: Koreeda, M.; Mislankur, S.G. J. Am. Chem. Soc, 1983, 105, 7203) which then undergoes further deprotonation to produce an aromatic 6-π anionic species that reprotonates to give 24.

Scheme 3. A possible mechanism for the formation of 24.

6π-aπlon Aromatic

The fact that 24 was co-produced in this cyclisation immediately raised concerns about whether compound 25 was being generated as a racemate. That 25 was being formed in optically pure condition was conclusively demonstrated by its large negative specific optical rotation in CHC1₃ ([α]_D -134° (c 0.5 CHC1₃)). Clearly, the pyrrole-N of 23 must be competitively and irreversibly adding to the enone at a rate faster than the γ- deprotonation and α-enolisation/protonation processes are proceeding according to Scheme 3, otherwise racemic 25 would almost certainly been the end-result. None of these events are at all obvious from Weinreb's published work on (+)-agelastatin A, since the formation of compound 24 was never discussed. The fact that 24 is always present in the reaction mixtures, makes it novel that (-)-25 should be generated from (-)-23 under these conditions; the obtention of homochiral product almost certainly would not have been predicted with any certainty. Indeed, it is contended that the only way the point could have been proved was by the cyclisation of (-)-23 being studied, as has been done (for the very first time) in the present invention.

The bromination of (-)-25 provides optically pure (-)-26 when carried out according to the Weinreb protocol; the latter is obtained in 58-74% yield with an [α]o of -112° in MeOH. He transformation of 25 to 26 may be carried out using a brominating agent such as NBS in a solvent such as THF.

Weinreb has previously converted (+)-26 into (+)-agelastatin A by a two-step, one-pot, operation. Therefore, it will now be possible to obtain (-)-agelastatin and its congeners from (-)-26.

In addition to the foregoing a new, alternative, synthetic pathway has been devised to provide (-)-agelastatins A and B from a key intermediate in the above formal route, namely, the oxazolidinone (-)-16. The new route now provides (-)-agelastatins A and B as a 4: 1 mixture enriched in the former molecule.

Thus, a further aspect of the present invention provides a process for enantiospecific synthesis of (-)-agelastatins A and B, characterised in that the process comprises a step of cleaving the SES group from a pyrrole carboxamide of the following formula:

29

under free radical conditions using an organotin hydride and a free radical initiator in a suitable solvent to provide a compound of the following formula:

30

Until now, it has proved difficult to remove a SES group whilst maintaining good yield. This aspect of the present invention provides surprisingly good yield (yields of 81-94% have been observed). The organotin hydride may comprise Bu SnH. The free radical initiator may comprise AIBN. The solvent may be any suitable organic solvent, such as benzene or toluene. Preferably, the reaction is carried out at reflux.

The pyrrole carboxamide 29 may be prepared from an oxazolidinone of the following formula:

28

by N-acylation on its sulfonamido nitrogen with the pyrrole acid chloride 18. The reaction may be carried out using DMAP and Et₃Ν in a non-protic organic solvent, such as THF.

The oxazolidinone 28 may be prepared by regioselective N-acylation of the oxazolidinone 16 with an acid chloride of the following formula:

27

or a similar compound. (Feldman, K.S. et al, loc. cit.). An organometallic base, such as n-BuLi, in an organic solvent, such as THF, may be used. This reaction has been found to proceed in 88-93% yield on multigram scale. The pyrrole carboxamide 30 is regioselectively ring-opened to form an allylic alcohol of the following formula:

31

This may be achieved, for example, using an inorganic base, such as LiOH, in a polar solvent, such as THF water.

This step is followed by oxidation of the allylic alcohol 31 to provide a cyclopentenone of the following formula:

32

This oxidation is preferably effected with a mild oxidative agent such as pyridinium dichromate (PDC) in DMF; certain other oxidants, such as tetra-«-propylammonium perruthenate, generally cause significant product decomposition and so are not recommended.

The cyclopentenone 32 is then subjected to Michael cyclisation. However, the direct Michael-cyclisation of 32, mediated by Cs₂CO₃ in MeOH, is ineffective at bringing about the desired conjugate addition of the pyrrole nitrogen to the enone system. Instead, a multiple enolisation/reprotonation process takes place exclusively, with the result that an olefm transposition occurs to give the more substituted and stable cyclopentenone IV:

IV

Similar isomerisations are observed with other inorganic bases. It appears that the nature of the -amino ketone protecting group, and the acidity of the pyrrole NH, both play a decisive role in determining whether Michael addition occurs in these systems ahead of α,γ-enone deprotonation, reprotonation, and alkene migration.

To date, our extensive investigations on 32 have shown that Michael cyclisation only occurs in the NH(CO)N(Me)Bn-substituted cyclopentenone systems when the trimethylsilyl group in the pyrrole component is replaced by an electronegative substituent such as bromine. The latter grouping may be introduced, for example, by treating 32 with excess N-bromosuccinimide (ΝBS) in a solvent such as THF at 0 °C for an extended period of time. However, it will be noted that the use of an excess of ΝBS may also cause some polybromination to occur. Thereafter, the cyclisation may be brought about by adding an excess of a mild organic base, such as triethylamine, to the crude reaction mixture, and stirring the reactants for a prolonged period of time; this overcomes the cyclopentenone isomerisation problem which is only an issue when strong bases are used in the ΝH(CO)Ν(Me)Bn substituted systems.

The following two faster-moving major products are usually observed in the above cyclisation mixtures, after they have been stirred overnight with Et₃N:

33 34

These products are not easily separated from one another by SiO₂ flash chromatography at this stage. On one occasion, however, both products were separated from one another by preparative TLC, and one of the products was identified as 33; the other was tentatively assigned as the N-bromo-C-alkylated 2,3-dibromopyrrole 34 based upon MS and ΝMR analysis. If the reaction is carried out in the presence of lesser quantities of ΝBS, the relative amount of product 33 is increased.

Given the difficulties encountered in separating this mixture at this stage, it may be partially hydrogenated in a solvent, such as methanol, in the presence of a mild base, such as ΝaOAc, and a suitable catalyst, such as Pd/C, to give a new mixture of products enriched in what are presumed to be the following compounds:

These are then hydrogenolysed further, for example with a catalyst such as Pd(OH)₂ on carbon in THF. The desired major product is then separated from the undesired minor byproducts, said desired major product having the following formula:

37

It is most important not to use methanol as the reaction solvent for the Pd(OH)₂ mediated hydrogenation step, as OMe for OH exchange readily occurs in the product 37 under these conditions, and it is not usually possible to readily hydrolyse this product back to 37 under mild aqueous acidic conditions without also causing significant product decomposition.

A further step in our synthesis of (-)-agelastatins A and B is the bromination of (-)-37, for example with NBS in a solvent such as THF/MeOH following the published procedure of Feldman and Saunders (Feldman, K.S., loc. cit.). A 4:1 mixture of optically pure (-)- agelastatins A and B in ca. 50% yield has been observed.

Thus, a new synthetic protocol has been devised for obtaining (-)-agelastatins A and B from the oxazolidinone 16. We believe that our new route will be readily modifiable for the production of novel analogues of general structures I and II provided a reasonably acidic nitrogen heterocycle is employed for the conjugate addition step.

A particularly prefeπ'ed embodiment of this aspect of the present invention is shown in Scheme 2:

(-)-Agelastatta B

Scheme 2

Thus, the process of this aspect of the present invention provides a very useful pair of compounds, (-)-agelastatins A and B, and can be readily modified to prepare analogue structures.

The present invention includes all of the intermediates shown in Scheme 2 and methods for their synthesis in enantiomerically pure form. In particular, the new process facilitates the production of a compound of general structure I:

General Structure I

or a pharmaceutically acceptable salt thereof,

wherein,

C— A or Z— C = independently a single or double bond;

A = O, N or C; Z = O, N or C; and R¹, R², R³, R⁷ and R⁸ are independently selected from H, C_1-10 alkyl, C _O cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR⁹, OH, NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂, NR⁹COR⁹, NHCO₂ ⁹, CO₂R⁹, CO₂H, COR⁹, CONHR⁹, CONR⁹ ₂, S(O)₂R⁹, S(O)R⁹, SONH₂, SO₂NHR⁹, NHS(O)₂R⁹ groups, or an optionally substituted heterocyclic group;

R⁹ = H, C_MO alkyl, C_1-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl;

The new process also facilitates in particular the production of a compound of general structure II:

General Structure II

or a pharmaceutically acceptable salt thereof, wherein,

C— A, X— Y, Y— Z, and Z— C = independently a single or a double bond;

A = O orN; and X, Y, and Z are independently selected from C, N, or O; and R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are independently selected from H, C_1-10 alkyl, C_1-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR⁹, SR⁹, OH, NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂, NR⁹COR⁹, NHCO₂ ⁹, CO₂R⁹, CO₂H, COR⁹, CONHR⁹, CONR⁹ ₂, S(O)₂R⁹, S(O)R⁹, SONH₂, SO₂NHR⁹, NHS(O)₂R⁹ groups, or an optionally substituted heterocyclic group; R⁹ = H, Ci.io alkyl, C_MO cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl; n in (X)„ is any number of atoms that will produce a partially unsaturated or fully saturated 3 to 8 membered ring system containing 0 to 3 O or N atoms.

According to a further aspect of the present invention there is provided at least one compound of general structure I and/or general structure II as hereinbefore defined for use as a medicament.

A therapeutically effective non-toxic amount of a compound of general structure I and/or general structure II as hereinbefore defined may be administered in any suitable manner, including orally, parenterally (including subcutaneously, intramuscularly and intravenously), or topically. The administration will generally be carried out repetitively at intervals, for example once or several times a day.

The amount of the compound of general structure I and/or general structure II that is required in order to be effective as an anti-diabetes, anticancer, anti-inflammatory agent or anti-AD agent for treating human or animal subjects will of course vary and is ultimately at the discretion of the medical or veterinary practitioner treating the human or animal in each particular case. The factors to be considered by such a practitioner, e.g. a physician, include the route of administration and pharmaceutical formulation; the subject's body weight, surface area, age and general condition; and the chemical form of the compound to be administered.

In daily treatment, for example, the total daily dose may be given as a single dose, multiple doses, e.g. two to six times per day, or by intravenous infusion for any selected duration.

The compound of general structure I and/or general structure II may be presented, for example, in the form of a tablet, capsule, liquid (e.g. syrup) or injection.

While it may be possible for the compounds of general structure I and/or general structure II to be administered alone as the active pharmaceutical ingredient, it is preferable to present the compounds in a pharmaceutical composition.

According to a further aspect of the present invention therefore there is provided a pharmaceutical composition containing a compound of general structure I and/or general structure II as hereinbefore defined, or a pharmaceutically acceptable salt thereof, as an active ingredient.

Such pharmaceutical compositions for medical use will be formulated in accordance with any of the methods well known in the art of pharmacy for administration in any convenient manner. The compounds of the invention will usually be admixed with at least one other ingredient providing a compatible pharmaceutically acceptable additive, carrier, diluent or excipient, and may be presented in unit dosage form. The carrier(s) must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

The possible formulations include those suitable for oral, rectal, topical and parenteral (including subcutaneous, intramuscular and intravenous) administration or for administration to the lung or another absorptive site such as the nasal passages.

All methods of formulation in making up such pharmaceutical compositions will generally include the step of bringing the compound of general structure I and/or general structure II into association with a carrier which constitutes one or more accessory ingredients. Usually, the formulations are prepared by uniformly and intimately bringing the compound of general structure I and/or general structure II into association with a liquid carrier or with a finely divided solid carrier or with both and then, if necessary, shaping the product into desired formulations.

Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, sachets, tablets or lozenges, each containing a predetermined amount of the compound of general structure I and/or general structure II; as a powder or granules; or a suspension in an aqueous liquid or non-aqueous liquid such as a syrup, an elixir, an emulsion or a draught. The compound of general structure I and or general structure II may also be presented as a bolus, electuary or paste.

A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing, in a suitable machine, the compound of general structure I and/or general structure II in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, surface active or dispersing agent. Moulded tablets may be made by moulding, in a suitable machine, a mixture of the powdered compound of general structure I and/or general structure II with any suitable carrier.

A syrup may be made by adding the compound of general structure I and/or general structure II to a concentrated, aqueous solution of a sugar, for example sucrose, to which may be added any desired accessory ingredient. Such accessory ingredient(s) may include flavourings, an agent to retard crystallisation of the sugar or an agent to increase the solubility of any other ingredient, such as a polyhydric alcohol, for example glycerol or sorbitol.

Formulations for rectal administration may be presented as a suppository with a usual carrier such as cocoa butter.

Formulations suitable for parental administration conveniently comprise a sterile aqueous preparation of the compound of general structure I and/or general structure II which is preferably isotonic with the blood of the recipient.

In addition to the aforementioned ingredients, formulations of this invention, for example ointments, creams and the like, may include one or more accessory ingredients, for example a diluent, buffer, flavouring agent, binder, surface active agent, thickener, lubricant and/or a preservative (including an antioxidant) or other pharmaceutically inert excipient.

The compounds of this invention may also be made up for administration in liposomal formulations which can be prepared by methods well-known in the art.

A further aspect of the present invention provides the use of at least one compound of general structure I and/or general structure II as hereinbefore defined, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of cancer.

A further aspect of the present invention provides the use of at least one compound of general structure I and/or general structure II as hereinbefore defined, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of diabetes. A further aspect of the present invention provides the use of at least one compound of general structure I and/or general structure II as hereinbefore defined, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of Alzheimer's disease.

A further aspect of the present invention provides the use of at least one compound of general structure I and/or general structure II as hereinbefore defined, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of inflammation.

It is still further preferable to present the compounds of general structure I and/or general structure II in the form of a pro-drug derivative, or a pharmaceutically acceptable salt thereof.

A further aspect of the present invention provides at least one compound of general structure I and or general structure II in the form of a pro-drug derivative, or pharmaceutically acceptable salt thereof, for use as a medicament.

According to a further aspect of the present invention there is provided a pharmaceutical composition comprising, as an active ingredient, at least one compound of general structure I and/or general structure II, or a pharmaceutically acceptable salt thereof, wherein the said composition is in the form of a pro-drug derivative.

The said pro-drug includes ester, amide or glycoside derivatives of the compounds of General Structures I and II. Methods for the preparation of such pro-drugs derivatives are well known to those skilled in the art

Such pro-drug molecules are capable of being converted to any of the compounds of the present invention, or indeed their pharmaceutically acceptable salts, under physiological conditions or through hydrolysis. This may lead to a more potent treatment as the conversion generally occurs in the body at or near to the treatment site. Furthermore, pro-drugs can be more stable and therefore have longer shelf lives and are easier to transport than their active counterparts.

Methods of preparing and administering these pro-drug derivatives and the pharmaceutical compositions in which they are contained are in accordance with the foregoing.

The pro-drug derivative as hereinbefore described may be used in the manufacture of a treatment for cancer, diabetes, Alzheimer's Disease or inflammation.

According to a further aspect of the present invention there is provided a method of treatment of cancer which comprises administering to a human or an animal in need of such treatment a therapeutically effective amount of a compound of general structure I and or II as hereinbefore defined or a pro-drug or pharmaceutically acceptable salt thereof.

According to a further aspect of the present invention there is provided a method of treatment of diabetes which comprises administering to a human or an animal in need of such treatment a therapeutically effective amount of a compound of general structure I and or II as hereinbefore defined or a pro-drug or pharmaceutically acceptable salt thereof.

According to a further aspect of the present invention there is provided a method of treatment of Alzheimer's disease which comprises administering to a human or an animal in need of such treatment a therapeutically effective amount of a compound of general structure I and or II as hereinbefore defined or a pro-drug or pharmaceutically acceptable salt thereof.

According to a further aspect of the present invention there is provided a method of treatment of inflammation which comprises administering to a human or an animal in need of such treatment a therapeutically effective amount of a compound of general structure I and or II as hereinbefore defined or a pro-drug or pharmaceutically acceptable salt thereof.

In order to determine the in vivo efficacy of Agelastatin A against human tumour cell lines a mouse xenograft study has been conducted using HCT116 cell line (colon cancer cells). Agelastatin A was dosed at 2.5 mg/kg to a test group and compared with a control group which was dosed with the vehicle compound alone at 20 ml/kg. The efficacy was evaluated by taking measurements of the actual tumour volumes. The results can be seen below:-

Table 1 -control group

Table 2-test group

A comparison of the results given in tables 1 and 2 show that a reduction in tumour growth of around 25% is observed when xenograft mice (HCT116) are dosed with Agelastatin A relative to mice dosed with the vehicle compound alone.

Experimental Procedures for the synthesis of (-)-26 from 2

Details are presented of the synthesis of (-)-26 from D-glucosamine hydrochloride via the optically pure aziridine 2, including the process improvements that have been made to the original Weinreb route for converting 17 to 26. An aspect of the present invention thus constitutes a formal enantiospecific total synthesis of (-)-agelastatin A and its congeners.

Methyl 4,6-0-benzylidene-2,3-dideoxy-2,3-(N-methoxycarbonyl)epimino-α-D-allo- pyranoside (3).

To a stirred solution of the 2,3-epimine 2 (10 g, 38 mmol) in dry CH₂C1₂ (100 mL) and dry pyridine (9.2 mL, 114 mmol) at 0 °C was added methyl chloroformate (3.6 mL, 45.6 mmol) dropwise over 10 min. When the addition was complete, the cooling bath was removed, and the reaction mixture was allowed to warm to room temperature. After stirring for 4.5 h, H₂O (100 mL) was added to the reaction mixture, and the resulting biphasic solution partioned in a separatory funnel. The organic layer was removed, and the aqueous fraction further extracted with CH₂C1₂ (3 x 150 mL). The combined organic layers were washed with 0.5 M aq. HCl (2 x 100 mL), brine (100 mL), dried over MgSO₄, filtered and concentrated in vacuo. The title compound 3 crystallised in pure condition when the crude residue was triturated with EtOAc and petrol; the product 3 was obtained in two crops (8.2 g and 2.3 g, 86% overall). [α]π +64.3 ° (c 0.12, CH₂C1₂); IR (KBr) 1724 (s), 1443 (s), 1416 (w), 1392 (m), 1366 (m), 1307 (s), 1220 (s), 1189 (w), 1137 (m), 1110 (s), 1065 (s), 1021 (s), 986 (s), 956 (m), 859 (w), 750 (m), 695 (m); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 7.49 (m, 2 H, arom.), 7.38-7.32 (m, 3 H, arom.), 5.56 (s, 1 H, Ph-CH-), 4.90 (d, J= 3.1 Hz, 1 H, HI), 4.20 (dd, J=10.2, 5.1 Hz, 1 H, H6), 4.01 (ddd, 1 H, H5), 3.84 (dd, J= 9.1, 1.6 Hz, 1 H, H4), 3.73 (s, 3 H, -CO₂CH₃), 3.65 (dd, J= 10.3, 10.3 Hz, 1 H, H6), 3.46 (s, 3 H, -OCH₃), 3.11 (narrow m, 2 H, H2 + H3); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 162.5 (CO), 137.2 (arom.), 128.3 (arom.), 126.4 (arom), 102.6 (PhCH-), 94.5 (CI), 76.3 (C4), 68.9 (C6), 60.1 (C5), 55.9 (-OCH₃), 54.1 (-CO2CH₃), 39.3 (C3/C2), 36.9 (C3/C2). HRMS Calcd for Cι₆H₂₀NO₆ (M+H)⁺: m/e 322.12905. Found: m/e 322.12876. Anal, for C₁₆H₁₉NO₆. Calcd. C: 59.81; H: 5.96; N: 4.36. Found. C: 59.83; H: 5.94; N: 4.30.

Methyl 2-azido-4,6-0-benzyIidene-2,3-dideoxy-3-methoxycarbonylamino-α-D-altro- pyranoside (4).

A mixture of 3 (8.2g, 25.5 mmol), NaN₃ (6.63 g, 102 mmol), and NHjCl (2.1 g, 40.8 mmol) in dry DMF (150 L) were heated at reflux for 4 h, whereafter TLC analysis (4:1 EtOAc:Petrol) revealed that all of 3 had been consumed and that a single slower- moving product 4 had formed. The reaction mixture was cooled to RT, H₂O (200 mL) was added, and the aqueous solution was extracted with EtOAc (3 x 200 mL). The combined organic layers were washed with H₂O (2 x 200 mL) and brine (100 ml), and dried over MgSO₄. After removal of the drying agent by filtration, the solvent was removed in vacuo. The resulting white solid was suspended in Et₂O (50 mL) and the pure product 4 (5.9 g, 65%) was isolated by suction filtration. The mother liquor was concentrated in vacuo, and the resulting white solid was recrystallised from Et₂O/Petrol. A further crop of pure 4 (2.27 g) was isolated thereafter. The combined overall yield of 4 = 8.17 g (88%). [α]_D +34.1 ° (c 0.5, CH₂C1₂); IR (KBr) 3423 (s), 2106 (s), 1736 (s), 1514 (s), 1458 (m), 1404 (m), 1374 (m), 1350 (m), 1315 (m), 1267 (s), 1221 (s), 1129 (s), 1091 (s), 1063 (s), 1048 (s), 1024 (s), 988 (s), 956 (s), 933 (m), 894 (m), 825 (m), 763 (m), 700 (m); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 7.43-7.38 (m, 2 H, arom.), 7.37-7.30 (m, 3 H, arom.), 5.64 (d, J= 9.0 Hz, 1 H, -NHCO₂Me), 5.61 (s, 1 H, Ph-CH-), 4.66 (s, 1 H, HI), 4.41 (m, 1 H, H3), 4.27 (dd, J= 10.1, 4.5 Hz, 1 H, H6), 3.98 (dd, J= 9.8, 4.0 Hz, 1 H, H4), 3.92 (m, 1 H, H5), 3.88 (s, 1 H, H2), 3.81 (dd, J= 10.2, 10.0 Hz, 1 H, H6), 3.67 (s, 3 H, -CO₂CH₃), 3.42 (s, 3 H, -OCH₃); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 156.6 (CO), 137.0 (arom.), 128.9 (arom.), 128.2 (arom.), 126.0- (arom.), 101.6 (Ph-CH-), 99.2 (CI), 74.0 (C4), 68.9 (C6), 61.2 (C2), 59.2 (C5), 55.7 (-OCH₃), 52.3 (-CO₂CH₃), 49.3 (C3). HRMS Calcd for d₆H₂₁N₄O₆ (M+H)⁺: m/e 365.14610. Found: m/e 365.14552. Anal, for C₁₆H₂₀N₄O₆. Calcd. C: 52.74; H: 5.53; N: 15.38. Found. C: 52.90; H: 5.25; N: 15.10.

Methyl 4,6-0-benzylidene-2,3-dideoxy-3-methoxycarbonylamino-2-trimethylsilyl- ethylsulfonamido-α-D-altropyranoside (6).

(ix) SESCI, AgCN, C₆H₆, 75 °C,

(61%, 2 steps)

A suspension of 20% Pd(OH)₂ on C (Aldrich, wet type) (2.7 g, 2.6 mmol) and azide 4 (9.4 g, 26 mmol) were suspended in MeOH (280 mL) and the reaction vessel was sequentially evacuated and purged with H₂ gas five times before being allowed to stir vigorously under a hydrogen atmosphere (1 atm) at room temperature for 3 h. The suspension was then filtered through a pad of Celite^® and the solvent concentrated in vacuo. The resulting oil 5 (8.3 g) was sufficiently pure for use in the next step and was not purified any further.

To a mixture of amine 5 (10.4 g, 30.7 mmol) and AgCN (6.2 g, 46.1 mmol) in freshly distilled C₆H6 was added SESCI (9.3 g, 46.1 mmol) in one portion. The reaction mixture was heated at 75 °C for 22 h and then cooled to room temperature before being filtered through Celite^®. The filtrate was concentrated in vacuo and the crude residue purified by SiO₂ flash chromatography with 3:1 Petro EtOAc as eluent. Compound 6 (9.4 g, 61%) was obtained as a pale yellow oil. [α]_D +18.2 ° (c 0.5, CH₂C1₂); IR (Neat) 3427 (w), 3267 (br w), 3016 (w), 2954 (m), 1721 (s), 1517 (s), 1455 (m), 1413 (w), 1376 (w), 1354 (w), 1324 (s), 1252 (s), 1147 (s), 1108 (s), 1070 (m), 1045 (s), 963 (w), 921 (m), 890 (m), 860 (s), 841 (s), 757 (s), 700 (m), 664 (w), 541 (w), 510 (w); 1H-NMR (400 MHz, toluene-d₈, 363.8 K) δ 7.41-7.38 (m, 2 H, arom.), 7.09-6.97 (m, 3 H, arom.), 5.38 (s, 1 H, Ph-CH-), 5.34 (br d, J = 8.6 Hz, 1 H, -NHCO₂Me), 4.76 (d, J = 9.4 Hz, 1 H, - NHSes), 4.62 (s, 1 H, HI), 4.30 (m, 1 H, H3), 4.00 (dd, 7= 10.2, 5.0 Hz, 1 H, H6), 3.90 (d, J= 8.4, 1.3 Hz, 1 H, H2), 3.72 (ddd, J= 10.0, 9.9, 5.0, 4.9 Hz, 1 H, H5), 3.58 (dd, J = 10.0, 4.7 Hz, 1 H, H4), 3.52 (dd, J = 10.1, 10.1 Hz, 1H, H6), 3.33 (s, 3 H, -CO₂CH₃), 2.99 (dd, J= 9.2, 8.3 Hz, 2 H, Ses), 2.92 (s, 3 H, -OCH₃), 1.06 (m, 2 H, Ses), -0.10 (s, 9 H, -TMS); ¹³C-NMR partial spectrum(125 MHz, toluene-d₈, 298 K) δ 156.9 (CO), 138.1 (arom.), 126.7 (arom.), 102.4 (CI), 102.1 (Ph-CH-), 74.1 (C4), 69.2 (C6), 59.2 (C5), 55.3 (C3), 55.2 (-OCH₃), 51.8 (-CO₂CH₃), 51.7 (C2), 50.2 (Ses), 11.0 (Ses), -2.1 (- TMS). HRMS Calcd for C₂₁H₃₄N₂O₈SSiNa (M+Na)⁺: m/e 525.17027. Found: m/e 525.16969.

Methyl 2,3-dideoxy-3-methoxycarbonylamino-2-trimethylsilylethyIsulfonamido-α- D-altropyranoside (7).

To a stirred solution of the protected diamino-sugar 6 (29.2 g, 58.1 mmol) in dry MeOH (290 mL) at 0 °C was added AcCI (12.4 mL, 174 mmol) dropwise over 40 min. The reactants were stirred at 0 °C for 1 h, and then allowed to warm to RT for 0.5 h. Solid NaHCO₃ was added until pH7 was attained, and the solvents removed in vacuo. The residue was taken up in EtOAc (300 mL), and the solution washed with H₂O (200 mL). The aqueous layer was extracted ftirther with EtOAc (3 x 100 mL). The combined organic layers were washed successively with brine (200 mL), and dried over MgSO₄. After filtration and concentration in vacuo, the residue was purified by SiO₂ flash chromatography initially with 2:3 EtOAc/Petrol to remove faster moving by-products, and then with EtOAc to elute the product 7 (20.4g, 85%) as an oil. [α]_D +35.6 ° (c 0.5, CH₂C1₂); IR (Neat) 3410 (very br, s), 2954 (s), 1711 (s), 1525 (s), 1321 (s), 1252 (s), 1137 (s), 1108 (s), 1053 (s), 862 (m), 841 (m), 757 (w); Η-NMR (500 MHz, CDC1₃, 298 K) δ 5.97 (d, J= 8.0 Hz, 1 H, -NHSes), 5.75 (br s, 1 H, -NHCO₂Me), 4.67 (s, 1H, Hi), 4.18 (m, 1 H, H3), 4.04 (dd, J= 9.7, 4.2 Hz, 1 H, H4), 3.89 (dd, J= 12.0, 3.3 Hz, 1 H, H6), 3.83 (dd, J = 12.0, 3.0 Hz, 1 H, H6), 3.68 (s, 3 H, -CO₂CH₃), 3.64 (m, 2 H, H2 + H5), 3.40 (s, 3 H, -OCH₃), 2.96 (m, 2 H, Ses), 2.48 (br s, 2 H, -OH), 0.99 (m, 2 H, Ses), 0.05 (s, 9 H, -TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 158.1 (CO), 101.1 (CI),

69.0 (C5), 63.4 (C4), 61.7 (C6), 55.6 (-OCH₃), 54.4 (C2), 53.1 (C3), 52.7 (-CO₂CH₃),

50.1 (Ses), 10.4 (Ses), -2.0 (-TMS). HRMS Calcd for C₁₄H₃₀N₂O₈SSiNa (M+Na)⁺: m/e 437.13898. Found: m/e 437.13846.

Methyl 2,3-dideoxy-3-methoxycarbonylamino-6-0-toluenesuIphonyl-2-trimethyl- silylethylsulfonamido-α-D-altropyranoside (8).

To a mixture of the diol 7 (15.5 g 37.4 mmol) and 4-dimethylaminopyridine (457 mg, 3.74 mol) in dry CH₂C1₂ (190 L) was added Et₃N (53 mL, 374 mmol). The reactants were cooled to 0 °C whereafter TsCI (7.46 g, 39.3 mmol) (freshly recrystallised from C₆H₆) was added portionwise over 1 h. Stirring was continued at 0 °C for a further 3 h, before the cooling-bath was removed, and the reaction mixture was allowed to warm to

RT, where it was maintained for a further 13 h. Saturated aq. NΗ CI (200 mL) was then added, and the biphasic mixture separated. The aqueous layer was extracted with CH₂C1₂

(2 x 100 mL), and the combined organic extracts were washed with brine (50 mL), dried

(MgSO₄) and filtered. The solvent was then removed in vacuo and the crude residue purified by SiO₂ flash chromatography (gradient elution 3:2 PetrokEtOAc to EtOAc) to give 8 (16.9 g, 79%) as a white foam. [α]_D +22.2 ° (c 0.5, CH₂C1₂); IR (Neat) 3412 (br m), 2955 (m), 1708 (s), 1598 (w), 1522 (s), 1452 (w), 1362 (s), 1324 (s), 1288 (w), 1253

(s), 1175 (s), 1140 (s), 1099 (s), 1055 (s), 981 (m), 839 (s), 758 (s); 1H-NMR (400 MHz,

CDC1₃, 328 K) δ 7.79 (d, J= 8.4 Hz, 2 H, Ts), 7.32 (d, J= 8.0 Hz, 2 H, Ts), 5.85 (d, J = 8.7 Hz, 1 H, -NHCO₂Me), 4.85 (d, J= 9.5 Hz, 1 H, -NHSes), 4.60 (s, 1 H, HI), 4.36 (dd, J = 11.2, 2.1 Hz, 1H), 4.25 (dd, J= 11.2, 5.3 Hz, 1 H, H6), 4.16 (m, 1 H,), 3.86-3.74 (m, 3 H,), 3.67 (s, 3 H, -CO₂CH₃), 3.37 (s, 3 H, -OCH₃), 2.96 (m, 2 H, Ses), 2.86 (br s, 1H), 2.42 (s, 3 H, Ts), 1.01 (m, 2 H, Ses), 0.06 (s, 9H); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 158.2 (CO), 145.0 (arom.), 132.7 (arom.), 129.9 (arom.), 128.0 (arom.), 100.8 (CI), 69.2 (C6), 67.1 (C5), 63.9 (C4), 55.7 (-OCH₃), 54.0 (C2), 52.9 (C3), 52.8 (-CO₂CH₃), 50.4 (Ses), 21.6 (Ts), 10.5 (Ses), -2.0 (-TMS). HRMS Calcd for C₂₁H₃₆N₂O₁₀S₂SiNa (M+Na)⁺: m/e 591.14783. Found: m/e 591.14793.

Methyl 2,3-dideoxy-3-methoxycarbonylamino-6-0-toluenesulphonyl-4- O-triethyl- silyl-2-trimethylsilylethyl-sulfonamido-α-D-altropyranoside (9).

To a stirred solution of 8 (22.5 g, 39.6 mmol) and 4-dimethylaminopyridine (484 mg, 3.96 mmol) in dry pyridine (200 mL) was added chlorotriethylsilane (9.96 mL, 59.3 mmol) dropwise over 5 min. The reactants were stirred at RT for 19 h, whereafter the solvent was removed in vacuo. The residue was taken up in EtOAc (200 mL) and sat. aq.

NILCl (200 mL) was added. The organic layer was separated. The aqueous layer was extracted with EtOAc (3 x 200 mL), and the combined organic layers were washed with brine (50 mL) before being dried (MgSO₄) and filtered. The solvent was removed in vacuo and the crude residue purified by SiO₂ flash chromatography (gradient elution 4:1

Petro EtOAc to EtOAc) to give 9 (24.1 g, 89%) as an oil. [α]_D +42.6 ° (c 0.31, CH₂C1₂);

IR (Neat) 3434 (br m), 2955 (s), 1726 (s), 1597 (w), 1517 (s), 1455 (w), 1366 (s), 1324

(s), 1251 (s), 1176 (s), 1138 (s), 1110 (s), 1059 (s), 1018 (m), 929 (m), 862 (s), 837 (s),

742 (m), 665 (w); Η-NMR (500 MHz, CDC1₃, 298 K) δ 7.78 (d, J = 8.3 Hz, 2 H, Ts), 7.34 (d, J= 8.6 Hz, 2 H, Ts), 5.44 (d, J= 9.6 Hz, 1 H, -NHCO₂Me), 4.67 (d, J= 9.7 Hz, 1

H, -NHSes), 4.52 (d, J= 2.4 Hz, 1 H, HI), 4.25 (dd, J= 10.9, 1.8 Hz, 1 H, H6), 4.14 (dd,

J= 10.8, 5.6 Hz, 1 H, H6), 3.98 (m, 1 H, H3), 3.82 (m, 1 H, H4), 3.74 (m, 1H, H5), 3.64

(s, 3 H, -CO₂CH₃) superimposed upon 3.62 (m, 1 H, H2), 3.31 (s, 3 H, -OCH₃), 2.97 (m, 2 H, Ses), 2.43 (s, 3 H, Ts), 1.01 (m, 2 H, Ses), 0.88 (t, J= 8.0 Hz, 9 H, Tes), 0.56 ( , 6 H, Tes), 0.05 (s, 9H, -TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 156.9 (CO), 145.0 (arom.), 133.0 (arom.), 129.9 (arom.), 128.0 (arom.), 101.4 (CI), 69.0 (C6), 68.3 (C5), 64.4 (C4), 55.7 (~OCH₃), 54.3 (C2), 52.8 (C3), 52.3 (-CO₂CH₃), 50.2 (Ses), 21.6 (Ts), 10.6 (Ses), 6.7 (Tes), 4.6 (TES), -2.0 (-TMS). HRMS Calcd for C₂₇H₅₀N₂Oι₀S₂Si₂Na (M+Na)⁺: m/e 705.23429. Found: m/e 705.23488.

Methyl 6-iodo-3-methoxycarbonylamino-2,3,6-trideoxy-4-0-triethylsilyl-2- trimethylsilylethylsulfonamido-α-D-altropyranoside (lO).

To a stirred solution of 9 (13 g, 19 mmol) in acetone (380 mL) was added Nal (28.5 g, 190 mmol). The reaction mixture was heated at reflux for 24 h, the solvent removed in vacuo, and the residue suspended in EtOAc (400 ml), washed with H₂O (200 mL), brine (50 mL) and then dried over MgSO₄. Filtration, and concentration of the filtate in vacuo, gave a residue that was purified by SiO₂ flash chromatography (gradient elution 85:15 to 7:3 Petro EtOAc). The title compound 10 (11.8 g, 98%) was obtained as a colourless oil. [α]_D +40.3 ° (c 0.27, CH₂C1₂); IR (Neat) 3434 (m), 3267 (m), 2956 (s), 2913 (s), 2879 (s), 2840 (w), 1729 (s), 1517 (s), 1451 (m), 1324 (s),1251 (s), 1136 (s), 1026 (s), 851 (s), 800 (m), 742 (s), 699 (w); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 5.52 (d, J= 9.6 Hz, 1 H, -NHCO₂Me), 4.82 (d, J= 10.1 Hz, 1 H, -NHSes), 4.67 (d, J= 2.0 Hz, 1 H, HI), 4.01 (m, 1 H, H3), 3.75 (m, 1 H, H4), 3.67 (m, 1 H, H2) superimposed upon 3.65 (s, 3 H, -CO₂CH₃), 3.48 (m, 2 H, H5 + H6) superimposed upon 3.45 (s, 3 H, - OCH₃), 3.27 (dd, J= 11.1, 8.0 Hz, 1 H, H6), 2.99 (m, 2 H, Ses), 1.03 (m, 2 H, Ses), 0.94 (t, J = 8.0 Hz, 9 H, Tes), 0.65 (m, 6 H, Tes), 0.04 (s, 9 H, Ses); ¹³C-NMR (125 MHz, CDCI₃, 298 K) δ 156.9 (CO), 101.5 (CI), 69.3 (C5), 68.5 (C4), 56.0 (-OCH3), 54.6 (C2), 53.0 (C3), 52.3 (-CO₂CH₃), 50.3 (Ses), 10.6 (Ses), 7.1 (C6), 6.8 (Tes), 4.7 (Tes), - 2.0 (-TMS). HRMS Calcd for C^FLtflN^SS^Na (M+Na)⁺: m/e 661.12718. Found: m/e 661.12809.

Alkenyl- Aldehyde 11.

To a stirred solution of iodide 10 (12.1g, 19 mmol) in THF:H₂0 (4:1, 380 L) was added Zn dust (24.9 g, 0.380 mol) (Aldrich 20,998-8) and the mixture heated at reflux for 3 h. The suspension was then cooled, diluted with EtOAc (400 mL) and filtered through Celite^®, and the filtrate thereafter washed with brine (2 x 100 mL), before being dried over MgSO₄. After filtration, the solvent was removed in vacuo and the residue purified by SiO₂ flash chromatography with 7:3 PetroP.EtOAc to give 11 as a colourless oil (8.43g, 92%). [α]_D +10.6 ° (c 0.4, CH₂C1₂); IR (Neat) 3334 (br m), 2956 (s), 2913 (s), 2878 (s), 1728 (s), 1644 (w), 1535 (s), 1458 (s), 1419 (s), 1329 (s), 1250 (s), 1171 (m), 1145 (s), 1101 (s), 1062 (s) 1010 (m), 861 (s), 840 (s), 744 (s); Mixture of 2 rotamers: α and β (3/1) ^!H-NMR (500 MHz, toluene-d₈, 363 K) δ 9.32 (s, 1 H, HI α), 9.23 (s, 1 H, HI β), 5.65 (ddd, J = 17.3, 10.4, 7.0 Hz, 1 H, H5 α), 5.60 (m, 1 H, H5 β), 5.17 (br d, J= 6.9 Hz, 1 H, -NHSes), 5.05 (ddd, J= 17.2, 1.3 Hz, 1 H, H6 α), 4.99 (ddd, J= 17.2, 1.3 Hz, H6 β), 4.94 (ddd, J= 10.4, 1.3 Hz, H6 α), 4.90 (m, IH, H6 β), 4.71 (d, J = 8.0 Hz, 1 H, -NHCO₂Me), 4.30 (dd, J= 7.2, 3.5 Hz, 1 H, H2 α), 4.25 (m, 1 H, H4 α), 4.15 and 4.10 (m, 2 H, H2 β + H4 β), 3.99 (m, 1 H, H3 α), 3.44 (s, 3 H, -CO₂CH₃ β), 3.40 (s, 3 H, -CO₂CH₃ α), 2.83 (m, 2 H, Ses α), 2.80 (m, 2 H, Ses β), 1.02 (m, 4 H, Ses α,β), 0.89 (t, J= 8.1 Hz, 9 H, Tes α), 0.83 (t, J= 7.9 Hz, 9 H, Tes β), 0.55 (q, J= 8.0 Hz, 6 H, Tes α), 0.46 (q, J= 8.0 Hz, 6 H, Tes β), -0.15 (s, 9 H, -TMS α), -0.16 (s, 9 H, -TMS β); ¹³C-NMR (125 MHz, toluene-d₈, 363 K) δ 196.9 (CI α), 195.2 (CI β), 137.7 (C5), 117.7 (C6), 74.7 (C4), 63.5 (C2 β), 62.8 (C2 α), 55.7 (C3), 51.5 (-CO₂CH₃), 50.0 (Ses α), 49.4 (Ses β), 10.5 (Ses), 6.2 (Tes α), 6.1 (Tes β), 5.0 (Tes α), 4.9 (Tes β), -2.8 (-TMS). HRMS Calcd for C₁₉H₄₀N₂O₆SSi₂Na (M+Na)⁺: m/e 481.22237. Found: m/e 481.22286. Cyclopentene-Oxazolidinone 16.

To a stirred solution of sulfone 12 (5.48 g, 24.5 mmol) and aldehyde 11 (8.4 g, 17.5 mmol) in freshly distilled THF (75 mL) at -20 °C was added potassium hexamethyldisilazide (0.5 M soln in PhMe, 126 mL, 63.0 mmol) dropwise over 30 min. The mixture was stirred at -20 °C for 2 h before H₂O (50 mL) was added, and the cooling bath removed. Most of the THF was removed by evaporation in vacuo, and the product extracted from the aqueous solution with EtOAc (400 mL). The combined organic layers were washed with H₂O (100 ml), 1M aq. HCl (2 x 50 mL), sat. aq. NaHCO₃ (50 mL), brine (100 mL) and dried over MgSO₄. Filtration, concentration in vacuo, and purification of the crude residue by SiO₂ flash chromatography with 85:15 PetrokEtOAc provided 13 as a colourless oil (5.07 g) slightly contaminated by tetrazole by-product.

The slightly impure diene 13 and the Grubbs-Hoveyda catalyst 14 (130 mg, 0. 208 mmol) were dissolved in freshly distilled C₆H₆ (390 mL) and the reaction mixture heated at reflux for 14 h. The solvent was removed in vacuo and the crude residue partially purified by SiO₂ flash chromatography with 88:12 PetrokEtOAc as eluent. Cyclopentene 15 (3.7 g) was obtained slightly contaminated with the aforementioned tetrazole derivative.

To a solution of the slightly impure cyclopentene 15 (3.15 g) in MeOH (140 mL) was added K₂CO₃ (4.83 g, ca. 34.9 mmol) and the mixture heated at reflux for 2 h before being allowed to stand overnight for 11 h. The solvent was removed in vacuo, and the residue was taken up in EtOAc (150 mL) and H₂O (100 mL). The organic layers were separated and the aqueous fraction extracted with EtOAc (2 x 50 mL). The combined organic layers were washed with H₂O (50 mL), brine (50 mL), and dried (MgSO ). Filtration and concentration in vacuo gave a residue that was purified by SiO₂ flash chromatography with 3:2 EtOAc.Petrol to give pure 16 as a foam (1.9 g, 41% for 3 steps). [α]_D -65.7 ° (c 0.38, CH₂C1₂); IR (Neat) 3350 (s), 3286 (s), 2959 (m), 2897 (w), 1765 (s), 1716 (s), 1538 (w), 1454 (s), 1420 (s), 1321 (s), 1253 (s), 1212 (w), 1137 (s), 1043 (s), 947 (s), 836 (s), 775 (s); 1H-NMR (500 MHz, DMSO-d₆, 298 K) δ 8.11 (s, 1 H, -NHCO-), 7.36 (s, 1 H, -NHSes), 6.02 (m, with appearance of a large s, 2 H, H5 + H6), 5.53 (m, 1 H, H6a), 4.17 (s, 1 H, H4), 4.01 (d, J= 7.1 Hz, 1 H, H3a), 2.96 ( , 2 H, Ses), 0.87 (m, 2 H, Ses), 0.04 (s, 9 H, -TMS); ¹³C-NMR (125 MHz, DMSO-d₆, 298 K) δ 157.1 (CO), 135.4 (alkene), 132.0 (alkene), 83.5 (C6a), 64.5 (C4), 60.6 (C3a), 48.2 (Ses), 10.0 (Ses), -1.9 (-TMS). HRMS Calcd for C_πH₂₁N₂O₄SSiNa (M+H)⁺: m/e 305.09912. Found: m/e 305.09997.

BOC-Cyclopentene oxazolidinone 17.

16 17

To a stirred solution of oxazolidinone 16 (1.22 g, 4.01 mmol), 4- dimethylaminopyridine (123 mg, 1 mmol), and Et₃N (0.62 ml, 4.4 mmol) in dry CH₂C1₂ (80 mL) was added a solution of Boc₂O (963 mg, 4.41 mmol) in CH₂C1₂ (1.1 mL) dropwise at RT over 10 min. The reactants were stirred at RT for 12 h, whereupon more Boc₂O (88 mg, 0.4 mmol) was added, and the stirring continued for a further 2 h. H₂O (40 mL) was added to the reaction mixture, and the organic layer separated. The aqueous layer was extracted with CH₂C1₂ (2 x 15 mL), and the combined organic layers washed with 1M aq. HCl (10 mL), sat. aq. NaHCO₃ (10 mL), dried (MgSO₄), and filtered. The solvent was removed in vacuo and the crude residue recrystallised from EtO Ac/petrol to provide 17 (807 mg, 50%) as a white crystalline solid. The mother liquors were concentrated in vacuo, and the residue purified by SiO₂ flash chromatography with 3:2 PetrohEtOAc to provide a further quantity of 17 (210 mg, 62% overall). [α]_D -88.0 ° (c 0.22, CH₂C1₂); IR (KBr) 3283 (s), 2979 (w), 1792 (s), 1724 (s), 1455 (m), 1366 (s), 1338 (s), 1251 (s), 1168 (s), 1138 (s), 1073 (s), 901 (m), 856 (s); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 6.14 (dd, J = 5.5, 2.1 Hz, 1 H, H5), 6.05 (ddd, J = 5.7, 1.7,1.5 Hz, 1 H, H6), 5.50 (br d, J= 7.4 Hz, 1 H, H6a), 4.60 (d, J= 7.9 Hz, 1 H, -NHSes), 4.53 (m, 2 H, H3 and H4), 3.10 (m, 2 H, Ses), 1.54 (s, 9H, Boc), 1.03 (m, 2 H, Ses), 0.05 (s, 9 H, TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 150.4 (CO), 150.2 (CO), 136.5 (C5), 131.8 (C6), 85.0 (Boc), 80.1 (C6a), 65.1 (C3a), 63.6 (C4), 50.3 (Ses), 27.9 (Boc), 10.5 (Ses), - 2.0 (TMS). HRMS Calcd for C₁₆H₂₈N₂O₆SSiNa (M+Na)⁺: m/e 427.13349. Found: m/e 427.13286.

5-TMS-Pyrrole-2-carboxamido-N-SES-Cyclopentene-Boc-Oxazolidinone 19.

To a suspension of lithio 2-TMS-pyrrole-5-carboxylate (3.3 g, 20.2 mmol) in freshly distilled CH₂C1₂ (30 mL) at 0 °C was added oxalyl chloride (1.8 mL, 20.4 mmol) followed by 4 drops of dry DMF. After 10 min, the ice-bath was removed, and the reactants were stirred at RT for 2 h. The resulting suspension of 18 and LiCl was taken up via a glass syringe (slightly greased) and added dropwise over 1.5 h via syringe pump (flow rate 20 mL/h) to a solution of the amide 17 (3.3 g, 8.16 mmol) and DMAP (100 mg, 0. 816 mmol) in dry THF (44 mL) and Et₃N (5.7 mL, 40.8 mol) at RT. After the addition was complete, TLC (7:3 petrohEtOAc) analysis indicated that none of the starting amide 17 remained. Sat. aq. NaHCO₃ (23 mL) was added in one portion, and the mixture was partitioned between brine (75 mL) and CH₂C1₂ (150 mL). The organic layer was separated, dried over MgSO₄, and filtered. The solvent was removed in vacuo and the residue was purified by SiO₂ flash chromatography with 4: 1 petrohEtOAc to give 19 (3.7 g, 80%) as a white foam. [ ]_D -127 ° (c 0.5, CH₂C1₂); IR (KBr) 3417 (m), 2959 (m), 2902 (w), 1817 (s), 1723 (s), 1629 (s), 1528 (w), 1440 (s), 1350 (s), 1277 (s), 1253 (s), 1188 (s), 1140 (s), 1054 (s), 843 (s), 751 (s), 699 (m); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 9.36 (br s, 1 H, NH), 6.81 (dd, J= 3.8, 2.3 Hz, 1 H, arom), 6.42 (dd, J= 3.8, 2.7 Hz, 1 H, arom.), 6.17 (dd, J= 5.9, 2.1 Hz, 1 H, H5), 6.13 (m, 1 H, H6), 5.62 (m, 2 H, H4 and H6a), 4.98 (dd, J= 7.4, 1.4 Hz, 1 H, H3a), 3.59 (ddd, J = 14.1, 13.8, 4.5 Hz, 1 H, Ses), 3.46 (ddd, J= 14.1, 13.8, 4.3 Hz, 1 H, Ses), 1.38 (s, 9 H, Boc), 1.08 (ddd, J= 13.7, 9.6 Hz, 1 H, Ses) superimposed upon 1.01 (ddd, J= 13.7 Hz, 4.7 Hz, 1 H, Ses), 0.26 (s, 9 H, TMS), 0.03 (s, 9 H, Ses); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 162.6 (CO), 150.9 (CO), 149.6 (CO), 140.3 (arom.), 134.5 (alkene), 133.1 (alkene), 126.9 (arom.), 119.2 (arom.), 117.3 (arom.), 84.7 (Boc), 81.4 (C6a), 71.3 (C4), 61.5 (C3a), 52.9 (Ses), 27.7 (Boc), 9.9 (Ses), -1.4 (TMS), -2.0 (Ses). HRMS Calcd for C₂₄H₃₉N₃O₇SSi₂ (M)⁺: m/e 569.20471. Found: m/e 569.20520.

5-TMS-Pyrrole-2-carboxamido- Cyclopentene-Boc-Oxazolidinone 20.

Protocol A. To a solution of the sulfonamide 19 (348 mg, 0.675 mmol) in dry DMF (3.5 mL) was added CsF (103 mg, 0.675 mmol) at RT and the mixture stirred at RT for 19 h before being heated at 50 °C for 1 h. After cooling to RT, H₂O (50 mL) was added and the aqueous solution was extracted with EtOAc (6 x 15 mL). The combined organic layers were washed with H₂O (10 mL) and brine (10 mL), dried (MgSO₄), and filtered.

The solvent was then removed in vacuo and the residue was purified by SiO₂ flash chromatography with 3:2 Petrol/EtOAc to give 20 (169 mg, 68%) as a yellow oil; 19 (58 mg) was also recovered. Data for 20: [α]_D -166 ° (c 0.274, CH₂C1₂); IR (Neat) 3293 (w),

2957 ( ), 1807 (s), 1725 (w), 1636 (m), 1550 (s), 1524 (m), 1365 (s), 1336 (s), 1252 (s),

1200 (s), 1155 (s), 1075 (s), 1041 (m), 842 (s), 756 (s) cm^-1; 1H-NMR (500 MHz,

CDC1₃, 298 K) 6 9.17 (br s, 1 H, NH), 6.57 (dd, J= 3.6, 2.3 Hz, 1 H, arom.), 6.35 (dd, J = 3.6, 2.7 Hz, 1 H, arom.), 6.31 (d, J= 7.9 Hz, 1 H, NH), 6.05 (s, 2 H, alkene), 5.61 (ddd,

J= 7.7, 1.8, 1.0 Hz, 1 H, H6a), 4.92 (m, 1 H, H3a), 4.68 (dd, J= 7.6, 1.4 Hz, 1 H, H4),

1.50 (s, 9 H, Boc), 0.23 (s, 9 H, TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 160.7 (CO), 151.4 (CO), 149.4 (CO), 136.7 (alkene), 136.5 (arom), 130.8 (alkene), 128.5 (arom), 118.3 (arom.), 110.0 (arom.), 84.5 (Boc), 81.2 (C6a), 62.8 (C4), 62.7 (C3a), 27.9 (Boc), -1.2 (TMS). HRMS Calcd for C₁₉H₂₇N₃O₅Si (M+H)⁺: m/e 406.17981. Found: m/e 406.17997.

Larger Scale Protocol B. To a stirred solution of the sulfonamide (3.56 g, 6.25 mmol) in dry DMF (30 mL) was added CsF (950 mg, 6.25 mmol) at RT and the mixture stirred at RT for 17.5 h before being heated at 50 °C for 5 h. After cooling to RT, H₂O (500 mL) was added and the aqueous solution extracted with EtOAc (3 x 200 mL). The combined organic layers were washed with H₂O (10 mL) and brine (10 mL), dried (MgSO₄), and filtered. The solvent was then removed in vacuo and the residue was purified by SiO₂ flash chromatography with 3:2 Petrol/EtOAc to give 20 (1.17 g, 46%) as a yellow oil.

5-TMS-Pyrrole-2-carboxamido-Cyclopentene-Boc-Oxazolidinone 25.

2 (-)-25 23

(7% overall from 20) (18% overall from 20)

To a solution of the protected oxazolidinone 20 (1.12 g, 2.77 mmol) in THF/H₂O (9:1, 70 mL) was added LiOH.H₂O (0.93 g, 22.2 mmol) in one portion. The solution was vigorously stirred at RT for 2 h. Excess silica gel was added, and the solvents removed in vacuo. Application of the silicated sample to the top of a column containing SiO₂ followed by elution with EtOAc afforded 21 and 22 (1.06 g) as an essentially inseparable mixture. 500 MHz 1H NMR analysis of the entire mixed sample of 21 and 22 indicated it was a 7:3 mixture enriched in 22. To a solution of the aforementioned mixture of 21 and 22 (ca. 2.64 mmol) in freshly distilled MeCN (53 mL) was added successively NMO (619 mg, 5.28 mmol), 4A MS (ca. 4 g), and TPAP (93 mg, 0.264 mmol), and the solution vigorously stirred at RT for 2 h. The solvent was then removed in vacuo, the crude residue taken up in EtOAc (50 mL) and the solution filtered through a pad of Celite^®, and the pad thoroughly washed with more EtOAc. The filtrate was concentrated in vacuo, and the residue partially purified by gradient elution SiO₂ flash chromatography (with 7:3 PetrohEtOAc progressing to EtOAc) to give a mixture of 23 and 21 (530 mg, in ca. 3:1 ratio according to 1H NMR analysis).

The aforementioned mixture of ketone 23 and oxazolidinone 21 (ca. 1.41 mmol) was dissolved in MeOH (140 mL) and Cs₂CO₃ (460 mg, 1.41 mmol) was added. The reactants were stirred vigorously at RT for 1 h whereafter a further quantity of Cs₂CO (1.84 g, 4 equiv) was added. Stirring was continued for a further 1 h, whereupon TLC analysis indicated that two faster-moving products had formed and that the starting oxazolidinone 21 remained. The mixture was partitioned between EtOAc (560 mL) and brine (140 mL). The layers were separated and the organic layer dried (MgSO ), filtered, and concentrated in vacuo. The crude residue was purified by SiO₂ flash chromatography with 7:3 Petrol:EtOAc to give 24 (72 mg, 7% from 20) initially as a white solid, followed by 25 (189 mg, 18% from 20) as a colourless oil, and finally, recovered oxazolidinone 21 (130 mg) as a white solid.

The respective spectral data for 24 and 25 are presented below.

Enaminone/pyrrole 24: IR ( Br) 3226 (s), 2957 (w), 1693 (s), 1662 (s), 1631 (s), 1545 (s), 1501 (s), 1426 (m), 1372 (s), 1308 (s), 1273 (s), 1248 (s), 1161 (s), 1057 (w), 964 (s), 843 (s), 736 (w); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 11.90 (s, 1 H, NH), 9.37 (s, 1 H, NH), 6.97 (dd, J= 4.5, 2.2 Hz, 1 H, arom.), 6.78 (br s, 1 H, NH), 6.45 (dd, J = 3.4, 2.8 Hz, 1 H, arom.), 3.33 (m, 2 H, CHb), 2.47 ( , 2 H, Clfc), 1.50 (s, 9 H, Boc), 0.26 (s, 9 H, TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 198.6 (CO), 158.4 (CO), 154.5 (CO), 149.5 (alkene), 138.2 (alkene), 129.4 (arom.), 118.9 (arom.), 117.3 (arom.), 112.4 (arom.), 82.2 (Boc), 31.7 (CH₂), 28.1 (Boc), 25.4 (CH₂), -1.2 (TMS). HRMS Calcd for Cι₈H₂₇N₃O₄Si (M+H)⁺: m/e 378.18489. Found: m/e 378.18492.

Desired Tricycle 25: [α]_D -134° (c 0.5 CHC1₃); IR (Neat) 3347 (br w), 2977 (w), 1765 (m), 1712 (m), 1665 (s), 1543 (m), 1366 (m), 1336 (m), 1251 (s), 1164 (s), 842 (s), 754 (s); 1H-NMR (500 MHz, MeOD, 298 K) δ 6.92 (d, J= 3.8 Hz, 1 H, arom.), 6.43 (d, J = 3.8 Hz, 1 H, arom.), 5.13 (ddd, J= 9.0, 4.5 Hz, 1 H, H4), 4.79 (br d, J= 4.0 Hz, 1 H, H2), 4.59 (apparent t, J= 4.4 Hz, 1 H, H3), 2.96 (dd, J= 19.1, 10.2 Hz, 1 H, H5), 2.17 (dd, J = 19.1, 9.1 Hz, 1 H, H5), 1.48 (s, 9 H, Boc), 0.36 (s, 9 H, TMS); ¹³C-NMR (125 MHz, MeOD, 298 K) δ 208.6 (CO), 162.2 (CO), 157.9 (CO), 139.7 (arom.), 126.8 (arom.), 121.1 (arom.), 116.0 (arom.), 81.4 (Boc), 63.7 (C2), 56.2 (C3), 51.4 (C4), 41.6 (C5), 28.6 (Boc), -0.5 (TMS). HRMS Calcd for Cι₈H₂₇N₃O₄Si (M+H)⁺: m/e 378.18489. Found: m/e 387.18418.

Pyrrole Bromide 26

To a stirred solution of the N-Boc-α-amino-ketone (-)-25 (110 mg, 0.292 mmol) in freshly distilled THF (21 mL) at 0 °C was added N-bromosuccinimide (62 mg, 351 mmol) in one portion. The reactants were stirred at 0 °C for 1 h and then at RT for a further 5 h. Sat. aq. ΝaHC0₃ (20 mL) and sat. aq. Na₂S₂O₃ (5 ml) were added to the mixture, and the product 26 extracted with EtOAc (3 x 50 mL). The combined organic layers were washed with brine (100 mL), dried (MgSO₄), and filtered. The solvent was then removed in vαcuo, and the crude residue purified by SiO₂ flash chromatography with 3:2 Petrol EtOAc to give (-)-26 (83 mg, 74%) as a colourless oil. [α]_D -112° in (c 0.66, MeOH); IR (Neat) 3334 (br w), 2979 (w), 1764 (s), 1711 (s), 1665 (s), 1554 (m), 1423 (s), 1378 (m), 1338 (s), 1251 (m), 1165 (s), 1062 (w), 751 (s); 1H-NMR (500 MHz, MeOD, 298 K) δ 6.93 (d, J= 4.1 Hz, 1 H, arom.), 6.35 (d, J= 4.1 Hz, 1 H, arom.), 5.22 (ddd, J= 9.1, 4.8, 4.7 Hz, 1 H, H4), 4.74 ( br d, 1 H, H2), 4.62 (apparent t, J= 4.6 Hz, 1 H, H3), 3.02 (dd, J= 19.1, 9.0 Hz, 1 H, H5), 2.13 (dd, J= 19.1, 9.2 Hz, 1 H, H5), 1.48 (s, 9 H, Boc); ¹³C-NMR (125 MHz, MeOD, 298 K) δ 208.3 (CO), 161.5 (CO), 157.8 (CO), 123.9 (arom.), 116.4 (arom.), 114.2 (arom.), 107.5 (arom.), 81.4 (Boc), 63.4 (C2), 55.5 (C3), 49.8 (C4), 39.8 (C5), 28.6 (Boc). HRMS Calcd for C₁₅Hι₈N₃O₄Br (M+H)⁺: m/e 384.05588. Found: m/e 384.05552.

(+)-26 has previously been converted into racemic agelastatin A by Weinreb et al. Enantiomerically pure (-)-26 will thus yield (-)-agelastatin A, if subjected to the same protocol.

Experimental Procedures for the Synthesis of (-)- gelastatin A and B from Oxazolidinone 16.

In this section, details are provided of the synthesis of (-)-agelastatins A and B from optically pure oxazolidinone 16.

Oxazolidinone 16

(i) n-BuLi, THF, -78 °C,

To a stirred solution of 16 (3.0 g, 9.86 mmol) in dry THF (95 mL) at -78 °C under N₂ was added dropwise over 2 min a solution of n-BuLi (6.2 mL, 1.6 M in hexanes, 9.92 mmol), and 15 min later, acid chloride 27 (3.6 g, 19.7 mmol) in dry THF (5 mL) was added dropwise over 5 min. The cooling bath was removed, the reaction mixture is allowed to warm to RT over 15 min, and the reaction vessel was then transferred to an oil bath and heated at reflux for 4 h. DABCO (6.6 g, 112.2. mmol) was then added in one portion and the heating at reflux was continued for 18 h. The reactants were then cooled to RT, and sat. aq. NH C1 (20 mL) and brine (30 L) were added, and the organic layer separated. The aqueous layer was then extracted with EtOAc (2 x 50 mL), and the combined organic layers were dried over MgSO₄, filtered, and concentrated in vacuo. The residue was dissolved in the minimum amount of CH₂C1₂ needed to fully solublise it, and applied to a SiO₂ flash column packed with petrol. The product was then gradient eluted with 7:3 PetrolrEtOAc through to to 1:1 PetroLEtOAc to give 28 (4.2 g, 93%) as a white solid.

Data for 28: IR (KBr) 2954 (w), 1769 (s), 1685 (s), 1482 (w), 1453 (m), 1420 (w), 1403 (w), 1370 (s), 1324 (s), 1284 (m), 1254 (m), 1203 (m), 1167 (w), 1135 (m), l l l l (w), 1079 (m), 1042 (m), 1003 (w), 987 (w), 945 (w), 892 (m), 856 (m), 840 (m), 809 (w), 795 (w), 752 (w), 733 (m), 718 (w), 697 (m); 1H-NMR (400 MHz, Tol-dg, 323K) δ 7.12- 6.90 (m, 5 H, Ph), 5.54 (dd, J= 5.7, 2.4 Hz, 1 H, H5), 5.40 (ddd, J= 5.7, 1.6, 1.6 Hz, 1 H, H6), 4.87 (dd, J= 7.3, 0.9 Hz, 1 H, H6a), 4.36 (d, J= 7.3 Hz, 1 H, H3a), 4.31 (d, J= 8.3 Hz, 2 H, CH₂), 4.26 (s, 1 H, H4), 3.98 (br s, 1 H, NH), 3.07-2.99 (m, 2 H, SES), 2.63 (s, 3 H, NMe), 1.07-0.95 (m, 2 H, SES), -0.06 (TMS); ¹³C-NMR (125 MHz, Tol-d₈, 323 K, some resonances overlap and are hidden by the NMR solvent peaks) δ 154.2 (CO), 152.3 (CO), 137.2 (arom.), 136.6 (C5), 131.8 (C6), 128.0 (arom.), 81.9 (C6a), 64.8 (C4), 64.3 (C3a), 53.9 (CH₂), 50.8 (SES), 36.0 (NMe), 11.3 (SES), -1.8 (TMS). HRMS Calcd for C₂₀H₃oN₃O₅SSi: (M+H)⁺ 452.16754. Found: 452.16673.

Pyrrole carboxamide 29

To a vigorously stirred suspension of the lithium carboxylate salt of 5- trimethylsilyl-pyrrole-2-carboxylic acid (800 mg, 4.23 mmol) in dry CH₂C1₂ (12 mL) under an N₂ atmosphere was added oxalyl chloride (370 mg, 4.23 mmol) in one portion followed by 2 drops of dry DMF. The reactants were stirred at RT for 3 h, and then taken up in a syringe, and added by syringe pump (flow rate 10 mL/h) to a solution of 3 (955 mg, 2.12 mmol) in dry THF (18 mL) containing freshly distilled Et₃N (1.5 mL, 10.6 mmol) and 4-dimethylaminopyridine (52 mg, 0.42 mmol). When the addition of 18 was complete, the reaction mixture was stirred at RT for 1.25 h, and sat. aq. NaHCO₃ (9 mL) was added. The mixture was then partitioned between brine (30 mL) and CH₂C1₂ (60 mL). The organic layer was separated, dried over MgSO₄, filtered and concentrated in vacuo. The residue was taken up in the minimum amount of CH₂C1₂ needed to fully dissolve it, and applied to a SiO₂ flash column packed with petrol. The product was then eluted with 4:1 PetrokEtOAc to give 29 (1.25 g, 98%) as a white foam. Although this run gave the product in 98% yield, other runs have given 29 in lower yields (52%); we therefore quote the lower yield as the more realistic amount of product that one can expect to obtain.

Data for 29; IR (neat) 3335 (w), 2955 (m), 2361 (w), 1777 (s), 1680 (s), 1537 (w), 1484 (w), 1452 (w), 1404 (w), 1351 (s), 1251 (s), 1149 (s), 1054 (m), 952 (w), 918 (w), 842 (s), 803 (w), 757 ( ), 700 ( ), 631 (w); 1H-NMR (400 MHz, Tol-d₈, 343 K) δ 9.51 (br s, 1 H, NH pyrrole), 7.35 (dd, J= 3.8, 2.2 Hz, 1 H, pyrrole), 7.24-7.19 (m, 4 H, Ph), 7.06 (m, 1 H, Ph), 6.35 (dd, J= 3.8, 2.5 Hz, 1 H, pyrrole), 5.54 (m, 1 H, H5), 5.51-5.43 (m, 3 H, H6 + H4 + H6a), 5.28 (m, 1 H, H3a), 4.48 and 4.40 (2 x br d, 2 H, CH₂), 3.79-3.71 (m, 1 H, SES), 3.59-3.51 (m, 1 H, SES), 2.73 (s, 3 H, NMe), 1.23-1.20 (m, 2 H, SES), 0.05 (s, 9 H, TMS), -0.08 (s, 9 H, TMS); ¹³C-NMR (100 MHz, Tol-d₈, 343 K.) δ 162.9 (CO), 154.4 (CO), 152.8 (CO), 141.3 (C6), 137.1 (C5), 134.1 (arom), 133.1 (alkene), 130.6 (pyrrole), 129.0 (arom.), 121.7 (pyrrole), 119.6 (pyrrole), 83.4 (C6a), 70.9 (C4), 62.2 (C3a), 53.7 (CH₂), 52.0 (SES), 35.7 (NMe), 10.6 (SES), -1.6 (TMS), -2.1 (TMS). HRMS Calcd for C₂₈H₄₀N₄O₆SSi₂Na: (M+Na)⁺ 639.20223. Found: 639.21130. Pyrrole carboxamide 30

29 30

To a degassed solution of the sulfonamide 29 (1.55 g, 2.59 mmol) in freshly distilled C₆H₆ (50 mL) under N₂ was added BU₃S11H (1.88 g, 6.47 mmol) and the mixture brought to reflux. AIBN (1.06 g, 6.47 mmol) was then added in 25 equal portions (42.4 mg, 0.1 equiv) approx. every 20 min over 7 h. The mixture was allowed to cool to RT, and the solvent removed in vacuo. The residue was purified by gradient elution SiO₂ flash chromatography with 4:1 Petrol/EtOAc to 3:2 Petrol/EtOAc, and the resulting oil further purified by SiO₂ flash chromatography with 3:2 Petrol/EtOAc to give 30 (945 mg, 81%) as a white foam.

Data for 30: IR (KBr) 2956 (m), 2362 (w), 1779 (s), 1696 (s), 1621 (m), 1577 (m), 1549 (w), 1521 (m), 1481 (w), 1455 (m), 1401 (w), 1354 (s), 1251 (m), 1194 (s), 1147 (w), 1051 (s), 992 (w), 960 (w), 842 (s), 800 (m), 760 (m); 1H-NMR (400 MHz, CDC1₃, 328 K) δ 9.12 (s, 1 H, NH pyrrole), 7.36-7.25 (m, 5 H, Ph), 6.52 (dd, J = 3.6, 2.3 Hz, 1 H, pyrrole), 6.36 (dd, J= 3.6, 2.7 Hz, 1 H, pyrrole), 6.10 (br s, 2 H, alkene), 5.93 (d, J= 6.9 Hz, 1 H, NHCO), 5.67 (d, J= 7.5 Hz, 1 H, H6a), 4.89 (m, IH, H3a), 4.74 (d, J=15.3 Hz, 1 H, CH₂), 4.53 (m, IH, H4), 4.52 (d, J= 15.3 Hz, IH, CH₂), 2.97 (s, 3 H, NMe), 0.26 (s, 9 H, TMS); ¹³C-NMR (125 MHz, CDC1₃, 328 K) δ 160.8 (CO), 153.6 (CO), 153.0 (CO), 136.5 (arom.), 136.4 (arom.), 136.1 (alkene), 131.7 (alkene), 128.8 (arom.), 128.7 (arom.), 127.8 (arom.), 127.6 (arom.), 118.4 (pyrrole), 110.1 (pyrrole), 82.8 (C6a), 63.8 (C3a), 61.7 (C4), 53.7 (CH₂), 36.1 (NMe), -1.2 (TMS). HRMS Calcd for C₂₃H₂₉N₄O₄Si: (M+H)⁺ 453.19528. Found: 453.19528. Allylic alcohol 31

To a vigorously stirred solution of oxazolidinone 30 (615 mg, 1.36 mmol) in THF:H₂O (9:1) (34 mL) at RT was added LiOH.H₂O (569 mg, 13.6 mmol) in one portion, and the solution stirred at RT for 78 h. A further portion of LiOH.H₂O (285 mg, 6.8 mmol) was added, and vigorous stirring continued for a further 16.5 h. The solvents were then removed in vacuo, and the residue taken up in EtOAc (100 mL) and brine (20 mL), and the layers partitioned in a separatory funnel. The EtOAc layer was separated and dried over MgSO₄; it was then filtered and concentrated in vacuo.

The residue was then purified by SiO₂ flash chromatography using EtOAc as eluent to give 31 (337 mg, 65%) as a white foam.

Data for 31: IR (neat) 3312 (m), 2956 (w), 1633 (s), 1555 (m), 1527 (s), 1453 (w), 1389 (w), 1339 (w), 1250 (m), 1203 (m), 1148 (w), 1049 (w), 950 (w), 841 (m), 758 (w), 699 (w); 1H-NMR (500 MHz, CDC1₃, 298 K) δ 7.50 (d, J = 5.8 Hz, 1 H, NH pyrrole), 7.28- 7.20 (m, 5 H, Ph), 6.83 (dd, J= 3.6, 2.3 Hz, 1 H, pyrrole), 6.41 (dd, J= 3.6, 2.7 Hz, 1 H, pyrrole), 6.18 (dd, J= 6.1, 1.4 Hz, H3), 6.07 (m, 1 H, H2), 5.08 (dd, J= 6.0, 6.0 Hz, 1 H, H4), 4.66 (br s, 1 H, HI), 4.49 (m, 2 H, CH₂), 4.19 (dd, J = 13.2, 7.1 Hz, 1 H, H4), 3.58 (br s, 1 H, OH), 2.84 (s, 3 H, NMe), 0.30 (s, 9 H, TMS); ¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 162.3 (CO), 159.0 (CO), 137.6 (arom.), 137.2 (C3), 135.8 (arom.), 133.1 (C2), 129.2 (arom.), 128.6 (arom.), 127.4 (arom.) 127.2 (arom.), 118.5 (pyrrole), 111.1 (pyrrole), 73.2 (CI), 60.0 (C4), 59.9 (C5), 52.2 (CH₂), 34.0 (NMe), -1.1 (TMS). HRMS Calcd for C₂₂H₃₁N₄O₃Si: (M+H)⁺ 427.21653. Found: 427.21697. Cyclopentenone 32

To a stirred solution of alcohol 31 (361 mg, 0.847 mmol) in DMF (8.5 mL) was added pyridinium dichromate (1.59 g, 4.23 mmol) and the mixture was stirred at RT for 1.5 h. The mixture was then partitioned between EtOAc (170 mL) and H₂O (30 mL), and the organic layer was separated and washed successively with H₂O (6 x 10 mL) and brine (10 mL). After being dried over MgSO₄, and filtered, the solvent was removed in vacuo. The residue was then purified by SiO₂ flash chromatography using 4: 1 EtO Ac/Petrol to give 32 (262 mg, 73%) as a white foam.

Data for 32: IR (neat) 2956 (m), 1725 (s), 1835 (s), 1553 (s), 1535 (s), 1452 (w), 1388 (w), 1335 (m), 1250 (m), 1199 (m), 1148 (w), 1117 (w), 1080 (w), 1049 (w), 979 (w), 842 (s), 798 (w), 759 (m), 699 (w); ^!H-NMR (500 MHz, CDC1₃, 298 K) δ 9.33 (br s, 1 H, NH pyrrole), 7.88 (d, J= 6.1 Hz, 1 H, alkene), 7.77 (br s, 1 H, NHCO pyrrole), 7.31-7.18 (m, 5 H, Ph), 6.77 (dd, J = 3.3, 2.4 Hz, 1 H, pyrrole), 6.38 (dd, J = 3.4, 2.7 Hz, 1 H, pyrrole), 6.29 (d, J= 6.1 Hz, 1 H, alkene), 5.32 (d, J= 1.4 Hz, 1 H, Bn), 4.71 (br s, 1 H, H4), 4.54 (d, J= 15.7 Hz, IH, CH₂), 4.40 (d, J= 15.7 Hz, CH₂), 4.37 (dd, J= 4.4, 4.3 Hz, 1 H, H5), 2.87 (s, 3 H, NMe), 0.24 (s, 9 H, TMS);

¹³C-NMR (125 MHz, CDC1₃, 298 K) δ 201.3 (CO ketone), 162.3 (CO), 160.7 (alkene),

158.9 (CO), 137.1 (arom.), 136.1 (arom.), 131.4 (alkene), 128.9 (arom.), 128.8 (arom.), 127.5 (arom.), 127.3 (arom.), 118.5 (pyrrole), 111.1 (pyrrole.), 62.7 (C5), 59.2 (C4), 52.3 (CH₂), 34.3 (NMe), -1.1 (TMS). HRMS Calcd for C₂₂H₂₉N₄O₃Si: (M+H)⁺ 425.20089. Found: 425.20174. (-)-DebromoageIastatin A

To a solution of the α,β-unsaturated ketone 32 (308 mg, 0.726 mmol) in dry THF (36 mL) at 0 °C was added N-bromosuccinimide (ΝBS) (155 mg, 0.871 mmol) in one portion. The mixture was stirred for 1 h at 0 °C and then at RT for 2 h. The reactants were cooled to 0 °C and more ΝBS (39 mg, 0.218 mmol) was added, and the mixture was stirred at RT for 3 h. After further cooling to 0 °C, a further quantity of ΝBS (26 mg, 0.145 mmol) was added and the reactants stirred for lh. The reaction mixture was then warmed to RT and Et Ν (735 mg, 7.26 mmol) was added dropwise, and stirring continued for a further 15 h. Sat. aq. a₂SO₃ (5 mL) was added to quench any excess NBS, followed by brine (20 mL). The aqueous solution was then extracted with EtOAc (2 x 50 mL) and the combined organic layers were dried over MgSO₄. After filtration, removal of the solvents in vacuo led to a residue that was partially purified by SiO₂ flash chromatography (3:2 EtO Ac/Petrol). The two main products of brominative cyclisation (33 and 34) were not readily separated from one another by this flash chromatographic purification and so were used directly for the next step.

A solution of the above product mixture containing 33 and 34 (210 mg, assumed to be ca. 0.486 mmol) was dissolved in MeOH (24 mL) and NaOAc (60 mg, 0.729 mmol) was added followed by 10% Pd on C (wet) (105 mg, ca. 0.0486 mmol), and the mixture hydrogenated under an atmosphere of H₂ at 1 atm for 2 h. The suspension was filtered through Celite, and the filtrate concentrated in vacuo. The residue was taken up in EtOAc (60 mL), washed with H₂O (10 mL) and brine (10 mL), dried over MgSO₄, filtered, and concentrated in vacuo. The resulting oil (145 mg), which was a mixture of products in which 35 predominated, was not purified any further but used directly for the next step.

To a solution of the crude 35/36 (145 mg, assumed to be 0.413 mmol) in freshly distilled THF (8 L) was added 20% Pd(OH)₂ on carbon (100 mg). The mixture was hydrogenated under a atmosphere of H₂ (1 arm) for 17 h at RT, and then filtered through Celite. The filter pad was washed with MeOH to remove all of the products, and the combined filtrate was concentrated in vacuo. The residue was then taken up in MeOH and applied to a 2 mm thickness SiO₂ preparative TLC plate, which was eluted with an 82:18 mixture of EtOAc/MeOH. The main product 37 was isolated from the plate in essentially pure condition but was further purified by SiO₂ flash chromatography to give 37 (18 mg, 10% over 3 steps) as a white solid.

Data for 37: 1H-NMR (400 MHz, MeOD, 298 K) δ 7.02 (dd, J = 2.5, 1.6 Hz, 1 H, HI), 6.88 (dd, J = 3.9, 1.5 Hz, 1 H, H3), 6.23 (dd, = 3.9, 2.6 Hz, 1 H, H2), 4.65 (dt, J= 10.4, 6.1 Hz, 1 H, H9a), 3.99 (dd, J= 5.3, 1.1 Hz, 1 H, H5a), 3.80 (d, J= 1.3 Hz, 1 H, H5b), 2.78 (3H, NMe), 2.61 (dd, J = 13.3, 6.4 Hz, 1 H, H9), 2.27 (dd, J= 13.3, 10.4 Hz, 1 H, H9); ¹³C-NMR (100 MHz, MeOD, 298 K) δ 162.1 (C7), 161.3 (C4), 125.7 (C3a), 122.9 (CI), 115.4 (C3), 111.1 (C2), 95.8 (C8a), 68.0 (C5b), 62.8 (C5a), 55.6 (C9a), 41.6 (C9), 24.3 (N-Me). LRMS (ES) Calcd for C₁₂H₁₅N₄O₃Na: (M+H+Na)⁺. Found: 284.9.

(-)-Agelastatins A and B

37 (-)-Agelastatin A (-)-Agelastatin B To a stirred solution of 37 (16 mg, 0.061 mmol) in MeOH (1.5 mL) and freshly distilled THF (3 mL) at RT was added N-bromosuccinimide (ΝBS) (10.9 mg, 0.0610 mmol). After 2.5 h, a further quantity of ΝBS (5.4 mg, 0.03 mmol) was added and the reactant stirred for a 0.5 h. The solution was then applied directly to a 1 mm thickness SiO₂ preparative TLC plate, which was eluted with 82:18 EtOAc/MeOH, to give a 4:1 mixture of (-)-agelastatins A and B (10 mg, ca. 50%) as a white solid after a further SiO₂ flash chromatographic filtration (same eluent).

Data for (-)-agelastatin A: 1H-ΝMR (500 MHz, MeOD, 298 K) δ 6.90 (d, J= 4.1 Hz, 1 H, H3), 6.32 (d, J = 4.1 Hz, 1 H, H2), 4.59 (m, 1 H, H9a), 4.08 (d, J= 5.5 Hz, 1 H, H5a), 3.88 (s, 1 H, H5b), 2.80 (s, 3 H, N-Me), 2.64 (dd, 7= 13.1, 6.5 Hz, 1 H, H9), 2.09 (dd, J = 12.6, 12.6 Hz, 1 H, H9); ¹³C-NMR (125 MHz, MeOD, 298 K) δ 161.4 (CI), 161.1 (C4), 124.1 (C3a), 116.0 (C3), 113.8 (C2), 107.2 (CI), 95.7 (C8a), 67.4 (C5b), 62.2 (C5a), 54.4 (C9a), 40.0 (C9), 24.2 (N-Me). LRMS (CI) Calcd for C₁₂Hι₃N₄O₃Br. Found: /e 341 (M)⁺.

Slightly contaminated with 20% (-)-agelastatin B

1H-NMR (500 MHz, MeOD, 298 K) δ 6.95 (s, 1 H, H3), 4.58 (d(app.)t, J = 12.0, 1 H, H9a), 4.10 (d, J= 5.4 Hz, 1 H, H5a), 3.87 (s, 1 H, H5b), 2.80 (s, 3 H, N-Me), 2.65 (m, 1 H, H9), 2.11 (dd, J= 12.7, 12.5 Hz, 1 H, H9); ); ¹³C-NMR (125 MHz, MeOD, 298 K) δ 161.4 (C7), 160.0 (C4), 124.7 (C3a), 116.9 (C3), 108.7 (CI), 101.7 (C2), 95.6 (C8a), 67.4 (C5b), 62.0 (C5a), 55.4 (C9a), 39.9 (C9), 24.2 (N-Me).

Claims

Claims:

A compound of general structure I:

(I) or a pharmaceutically acceptable salt thereof, wherein,

C— A and Z— C = independently a single or a double bond;

A = C, N, O, S, or Se; Z = C, N, O, S, or Se;

R¹, R ², R³, R⁷ and R⁸ are independently selected from H, C_1-10 alkyl, Cι_-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR⁹, SR⁹, OH,

NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂, NR⁹COR⁹,

NHCO₂R⁹, CO₂R⁹, CO₂H, COR⁹, CONHR⁹, CON(R⁹)₂, S(O)₂R⁹, S(O)R⁹, SONH₂, SO₂NHR⁹, NHS(O)₂R⁹, and Si(R⁹)₃ groups, or an optionally substituted heterocyclic group; and

R = H, Ci.io alkyl, C_1-10 cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl.

2. A compound according to claim 1, wherein when Z is S R⁷ is a single O or a pair of O groups and R is an alkyl, a cycloalkyl, an aryl or a heteroaryl group.

3. A compound of general structure II:

(II)

or a pharmaceutically acceptable salt thereof, wherein,

C— A, X— Y, Y— Z, and Z— C = independently a single or a double bond;

A, X, Y and Z = independently selected from C, N, O, S, or Se;

R¹, R ², R³, R ⁴, R⁵, R⁶, R⁷ and R⁸ are independently selected from H, C ₀ alkyl, C_Wo cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl, halogen, haloalkyl, OR⁹, SR⁹, OH, NO₂, CN, NH₂, NHR⁹, N(R⁹)₂, NHOR⁹, NHCONHR⁹, NHCONR⁹ ₂,

NR⁹COR⁹, NHCO₂R⁹, CO₂R⁹, CO₂H, COR, CONHR, CONR⁹ ₂, S(O)₂R⁹, S(O)R⁹,

SONH₂, SO₂NHR⁹, NHS(O)₂R⁹, and Si(R⁹)₃ groups, or an optionally substituted heterocyclic group or R³ and R ⁴, R⁵ and R⁶, and R⁷ and R⁸ are taken together and selected from O, 0(R⁹)₂, =S, =NR⁹, =Se; and R⁹ = H, Ci.io alkyl, .io cycloalkyl, aryl, substituted aryl, optionally substituted alkylaryl; n is any number of atoms that will produce a partially unsaturated or fully saturated 3 to 8 membered ring system containing 0 to 3 heteroatoms.

4. A process for enantiospecific synthesis of (-)-agelastatin A from D- glucosamine hydrochloride, wherein said process involves the enantiospecific synthesis of Boc- cyclopentene oxazolidinone.

5. A process according to claim 4, wherein Boc cyclopentene oxazolidinone is prepared by N-acylating a compound of the following formula:

ES

using a suitable reagent in the presence of a catalyst.

6. A process according to claim 5, wherein the reagent is Boc₂O with the catalyst is as DMAP.

7. A process according to any one of claims 4 to 6 wherein the process comprises a step of preparing an oxazolidinone of the following formula:

ES in the presence of a base.

8. A process according to claim 7 wherein the base is potassium carbonate.

9. A process according to any one of claims 4 to 8 wherein the process comprises a step of preparing a compound of the following formula :

by way of metal catalysed metathesis reaction.

10. A process according to claim 9 wherein the said reaction is catalysed by a ruthenium catalyst of the following formula:

11. A process according to any one of claims 4 to 10, wherein the process further comprises a step of preparing a compound of the following formula:

using an anion derived from the following sulfone.

12. A process according to any one of claims 4 to 11, wherein the process further comprises a step of preparing a compound of the following formula:

by way of a Vasella reductive ring opening reaction.

13. A process according to any one of claims 4 to 12, wherein the process further comprises a step of preparing a compound of the following formula:

by way of a nucleophilic displacement reaction using a halide source.

14. A process according to claim 13, wherein the halide source is sodium iodide.

15. A process according to any one of claims 4 to 14, wherein the process further comprises a step of preparing a compound of the following formula:

16. A process according to claim 15, wherein the silyl halide compound is triethyl silyl chloride which is used in the presence of DMAP and a suitable base.

17. A process according to claim 16, wherein the base is pyridine.

18. A process according to any one of claims 4 to 17, wherein the process comprises a step of selectively protecting a compound of the following formula:

its primary alcohol using a suitable reagent to afford a compound of the following formula:

19. A process according to claim 18, wherein the said reagent comprises tosyl chloride which is used in the presence of a catalyst and suitable base.

20. A process according to claim 19, wherein the catalyst is DMAP.

21. A process according to any one of claims 4 to 20, wherein the said process comprises a step of hydrolysing a protected amino pyranoside of the following formula:

using an acid chloride in a protic solvent to afford a diol of the following formula:

22. A process according to claim 21, wherein the acid chloride is aectyl chloride.

23. A process according to claim 21 or claim 22, wherein the said solvent is MeOH.

24. A process according to any one of claims 4 to 23, wherein the process further comprises a step of preparing an amino pyranoside of the following formula:

using a silyl halide.

25. A process according to claim 24, wherein the said silyl halide is SESCI which is used in the presence of silver cyanide.

26. A process according to any one of claims 4 to 25, wherein the process further comprises a step of preparing a compound f the following formula:

by catalytic hydrogenolysis.

27. A process according to claim 26, wherein the hydrogenolysis is catalysed by Pearlman's catalyst.

28. A process according to any one of claims 4 to 27, wherein the process comprises a step of regioselectively ring opening a compound of the following formula:

using a nucleophilic reagent to provide an azide of the following formula:

29. A process according to claim 28, wherein the nucleophilic reagent comprises sodium azide.

30. A process according to claim 4 or claim 5, wherein the process comprises a step of N-acylating the compound of claim 5 using an acid chloride in the presence of a catalyst to afford a compound of the following formula:

31. A process according to claim 30, wherein the said acid chloride is of the following formula:

32. A process according to claim 30 or claim 31, wherein the catalyst is DMAP.

33. A process according to claim 4, claim 5 or any one of claims 30 to 32, wherein the said process comprises a step of cleaving an SES group of the compound of claim 30 using a fluoride ion source to provide a compound of the following formula:

34. A process according to claim 33, wherein the fluoride ion source is caesium fluoride.

35. A process according to claim 4, claim 5 or any one of claims 30 to 34, wherein the process comprises a step of selective hydrolysing the compound of claim 33 using a base to provide a compound of the following formula:

36. A process according to claim 35, wherein the said base is lithium hydroxide.

37. A process according to claim 4, claim 5 or any one of claims 30 to 36, wherein the process comprises a step of oxidising the compound of claim 35 using a transition metal oxidising agent to afford a compound of the following formula:

38. A process according to claim 37, wherein the said oxidising agent is TPAP and this is employed in the presence of NMO.

39. A process according to claim 4, claim 5 or any one of claims 30 to 38, wherein the process comprises a step of preparing an oxazolidinone of the following formula:

by way of base mediated cylisation reaction.

40. A process according to claim 39, wherein the base is caesium carbonate.

41. A process according to claim 4, claim 5 or any one of claims 30 to 40, wherein the process comprises a step of brominating the compound of claim 39 using a suitable brominating agent to provide a compound of the following formula:

42. A process according to claim 41, wherein the brominating agent is NBS.

43. A process for enantiospecific synthesis of (-)-agelastatins A and B, characterised in that the process comprises a step of cleaving an SES group a pyrrole carboxamide of the following formula:

under free radical conditions using an organotin hydride and a free radical initiator in a suitable solvent to provide a cyclopentene compound of the following formula:

44. A process according to claim 43, wherein the organotin hydride is tributyl tin hydride.

45. A process according to claim 43 or 44, wherein the free radical initiator is AIBN.

46. A process according to any one of claims 43 to 45, wherein the process comprises a step of N-acylating the cylopentene compound of claim 43 using an acid chloride in the presence of an organometallic base in a suitable solvent to provide a cyclopentene of the following formula:

47. A process according to claim 46, wherein the acid chloride is of the following formula:

O ci- N^

Me

48. A process according to claim 46 or 47, wherein the organometallic base is n- BuLi.

49. A process according to any one of claims 43 to 48, wherein the process comprises a step of N-acylating the cyclopentene compound of claim 46 at its sulfonamido nitrogen with an acid chloride in the presence of a catalyst.

50. A process according to claim 49, wherein the acid chloride is of the following formula:

// \\

TMS^N COCl H

51. A process according to claim 49 or 50, wherein the catalyst is DMAP.

52. A process according to any one of claims 43 to 51 , wherein the process comprises a step of preparing an allylic alcohol of the following formula:

using a base in a suitable solvent.

53. A process according to claim 52, wherein the base is lithium hydroxide.

54. A process according to any one of claims 43 to 53, wherein the process comprises a step of oxidising the allylic alcohol of claim 52 using a suitable oxidising agent to provide a compound of the following formula:

55. A process according to claim 54, wherein the oxidising agent is pyridium dichromate.

56. A process according to any one of claims 43 to 53, wherein the process comprises a step of preparing pyrrole compounds of the following formulas:

ing a suitable brominating agent.

57. A compound according to claim 56, wherein the brominating agent is NBS.

58. A process according to any one of claims 43 to 57, wherein the process comprises a step of partially hydrogenating the compounds of claim 56 in the presence of a mild base and a suitable catalyst to afford compounds of the following formulas:

59. A process according to claim 58, wherein the mild base is NaOAc.

60. A process according to claim 58 or claim 59, wherein the catalyst is Pd/C.

61. A process according to any one of claims 43 to 60, wherein the process comprises a step of hydrogenating the compounds of 58 with a suitable catalyst to provide a compound of the following formula:

62. A process according to any one of claims 43 to 61, wherein the process comprises a step of brominating the compound of claim 61 using a suitable brominating agent to provide a mixture comprising (-)-agelastatin A and (-)-agelastatin B.

63. A process according to claim 62, wherein the brominating agent is NBS.

64. A compound according to any of claims 1 to 3 for use as a medicament.

65. A pharmaceutical composition comprising as an active ingredient at least one compound according to any of claims 1 to 3.

66. A pharmaceutical composition comprising as an active ingredient at least one compound according to any of claims 1 to 3, wherein said composition is in the form of a pro-drug derivative.

67. A composition according to claim 66, wherein the prodrug derivative is selected from any of the following either alone or in combination: ester, amide or glycoside.

68. The use of a compound according to any of claims 1 to 3 in the manufacture of a medicament for the treatment of cancer.

69. The use of a compound according to any of claims 1 to 3 in the manufacture of a medicament for the treatment of diabetes.

70. The use of a compound according to any of claims 1 to 3 in the manufacture of a medicament for the treatment of Alzheimer's disease.

71. The use of a compound according to any of claims 1 to 3 in the manufacture of a medicament for the treatment of inflammation.