IE912254A1

IE912254A1 - Amino acid derivatives

Info

Publication number: IE912254A1
Application number: IE225491A
Authority: IE
Original assignee: Hoffmann La Roche
Priority date: 1990-06-28
Filing date: 1991-06-27
Publication date: 1992-01-01
Also published as: PT98123A; MX26375A; NO912537L; HUT61299A; BR9102730A; FI913179A0; EP0464572A2; NZ238645A; FI913179A; CA2044564A1; YU111991A; IS3725A7; ZA914808B; JPH04230380A; AU642021B2; AU7927891A; EP0464572A3; IL98576A0; KR920000762A; HU912097D0

Abstract

The compounds of the formula in which A, B, X, Y, R<1>, R<2>, R<3>, R<4> and R<5> have the meaning given in Claim 1, in the form of optically pure diastereomers, diastereomer mixtures, diastereomeric racemates or mixtures of diastereomeric racemates and pharmaceutically utilisable salts thereof inhibit the action of the natural enzyme renin and can therefore be used in the form of pharmaceutical preparations in the control or prevention of high blood pressure and cardiac insufficiency. They can be prepared by various processes known per se.

Description

The present invention is concerned with amino acid derivatives. In particular, it is concerned with amino acid derivatives of the general formula wherein one of A and B signifies a nitrogen atom and the other signifies -CH- or both signify a nitrogen atom, one of X and Y signifies a nitrogen atom and the other signifies -CH- or both signify -CH-, R1 . . . signifies phenyl, pyridyl or thienyl, R signifies alkyl or arylalkyl, R signifies hydrogen, alkyl, iraidazo1-2-ylmethyl. imidazol-4-ylmethyl. pyridylmethyl, pyrazol-3-ylmethyl. thien-2-ylmethyl, thiazol-4-ylmethyl. alkylthiomethyl. carbamoylmethyl. carbamoylethyl or benzyl, R signifies cyclohexyl5 methyl, benzyl or isobutyl and R signifies one of the groups OH ί (CH)m-R6 (h) (a) and in which R signifies cycloalkyl, alkyl, alkenyl or Kbr/15.5.91 - 2 arylalkyl. m signifies the number 2 or 3 and n signifies the number 3 or 4, in the form of optically pure diastereomers. mixtures of diastereomers. diastereomeric racemates or mixtures of diastereomeric racemates as well as pharmaceutically usable salts of these compounds.

These compounds are novel and are distinguished by valuable pharmacodynamic properties.

Objects of the present invention are the compounds of formula I and their pharmaceutically usable salts per se 3_5 and for use as therapeutically active substances, the manufacture of these compounds, medicaments containing these and the manufacture of such medicaments, as well as the use of compounds of formula I and their pharmaceutically usable salts in the control or prevention of ill20 nesses or in the improvement of health, especially in the control or prevention of high blood pressure and cardiac insufficiency.

The term alkyl used in the present description. alone or in combination, signifies straight-chain and branched hydrocarbon residues with 1-8. preferably 1-4. carbon atoms such as methyl, ethyl, n-propyl. isopropyl, n-butyl. isobutyl, sec.-butyl, t-butyl. pentyl, hexyl and the like. The term alkoxy signifies alkyl ether groups 30 in which the term alkyl has the above significance, such as methoxy, ethoxy, propoxy, isopropoxy. butoxy, isobutoxy, sec.-butoxy, t-butoxy and the like. The term cycloalkyl signifies saturated, cyclic hydrocarbon residues with 3-8, preferably 3-6, carbon atoms such as 35 cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like. The term alkenyl relates to straight-chain and branched, unsaturated hydrocarbon residue with 2-8, preferably 2-4. carbon atoms such as vinyl, allyl. 2IE 912254 - 3 -butenyl, 3-butenyl and the like. The term alkanoyloxy signifies the acid residue of a straight-chain or branched alkanoic acid with 1-8. preferably 1-4, carbon atoms attached via an oxygen atom, such as formyloxy. acetyloxy, propionyloxy, butyryloxy, valeryloxy, isovaleryloxy and the like. The term arylalkyl denotes straight-chain or branched alkyl groups in which in which one or more hydrogen atoms have been replaced by aryl groups, whereby the term aryl*1 signifies a mono- or bicyclic aromatic hydrocarbon residue with 6-14 carbon atoms which is optionally mono- or multiply-substituted by alkyl, alkoxy, alkanoyloxy. amino, alkylamino. dialkylamino, alkyl15 carbonylamino. hydroxy, halogen, trifluoromethyl or nitro, such as phenyl, a- or β-naphthyl. indenyl. anthryl or phenanthryl and the like. Examples of arylalkyl groups are benzyl, diphenylmethyl. trityl, a- or B-naphthylmethyl. 2-phenylethyl, 3-phenyl-2-propyl. 4-phenyl-320 -butyl. 2-(a- or β-naphthyl)ethyl. 3-a-naphthyl-2-propyl, 4-a-naphthyl-3-butyl and the like, whereby the aromatic residue can in each case be mono- or multiply-substituted as indicated above.

The term pharmaceutically usable salts'* embraces salts with inorganic or organic acids such as hydrochloric acid, hydrobromic acid, nitric acid, sulphuric acid, phosphoric acid, citric acid, formic acid, maleic acid, acetic acid, succinic acid, tartaric acid, methane30 sulphonic acid, p-toluenesulphonic acid and the like.

Such salts can be manufactured readily by any person skilled in the art having regard to the state of the art and taking into consideration the nature of the compound to be converted into a salt.

The compounds of formula 1 have at least three asymmetric carbon atoms and are therefore present in the form of optically pure diastereomers. mixtures of diastereoIE 912254 - 4 mere, diastereomeric racemates or mixtures of diastereomeric racemates. The present invention embraces all forms. Mixtures of diastereomers, diastereomeric racemates or mixtures of diastereomeric racemates can be separated according to usual methods, e.g. by column chromatography, thin-layer chromatography, HPLC and the like.

Those compounds of formula I in which A and B each signify a nitrogen atom are preferred. X preferably signifies a nitrogen atom and Y preferably signifies -CH-. Compounds of formula I in which R1 signifies pyridyl, especially 3-pyridyl. are also preferred. R preferably signifies alkyl or phenylalkyl. especially propyl, isopropyl, isobutyl. 1-methylpropyl or benzyl.

The preferred meaning of R3 is hydrogen, imidazol-2-ylmethyl. imidazol-4-ylmethyl or pyridylmethyl. especially imidazol-4-ylmethyl or pyridyl-3-methyl. Cyclohexyl4 5 methyl is the preferred meaning for R . R preferably signifies group (a). The preferred meaning for m is the number 2 and the preferred meaning for R6 is cycloalkyl.

From the above it follows that there are particularly preferred those compounds of formula I in which A. B and X each signify a nitrogen atom, Y signifies -CH-, R1 sig2 nifies 3-pyridyl. R signifies propyl, isopropyl. isobutyl, 1-methylpropyl or benzyl. R3 signifies imidazol4 . . . -4-methyl or pyridyl-3-methyl. R signifies cyclohexylmethyl and R5 signifies group (a) in which m signifies the number 2 and R6 signifies cycloalkyl.

Especially preferred compounds of formula 1 are: (R or S)-N-[(lS.2R.3S)-l-(Cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-a.6-bis(3-pyridyl)-striazolo[4.3-a]pyrazine-3-acetamide.

(R or S)-N-[(lS,2R.3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-8-isopropyl-α-(imidazol-4-ylmethy1)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide, (R or S)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclohexyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-8-isobutyl-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate, (R or S)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-2.3-dihydroxy-5-methylhexyl]-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetamide, (S or R)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-8-[(RS)-1-methylpropyl]-a-(3-pyridylmethy1)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide and N-[(1S.2R.3S)-1-(eyelohexyImethy1-3-cyclopropyl-2,3-dihydroxypropyl]-8-[(RS)-1-methylpropyl]-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-carboxamide.

The compounds of formula I in the form of optically pure diastereomers. mixtures of diastereomers. diastereoroeric racemates or mixtures of diastereomeric racemates as well as pharmaceutically usable salts thereof can be manufactured by a) reacting a compound of the general formula ... wherein R and R have the significance given above. with a compound of the general formula II . 12 3 wherein A. B. X, Y. R , R and R have the significance given above, or an activated derivative thereof, and b) if desired, separating a mixture of diastereomeric racemates into the diastereomeric racemates or optically pure diastereomers, and/or c) if desired, separating a mixture of diastereomers into the optically pure diastereomers. and/or d) if desired, converting a compound obtained into a pharmaceutically usable salt.

The acylation of a compound of formula II is effected according to methods known per se. Especially suitable acylating agents are activated acid derivatives 6uch as esters, mixed esters, acid halides and acid anhydrides or mixed anhydrides. The reaction is carried out in an organic solvent or solvent mixture which is inert under the reaction conditions at a temperature between about O’C and room temperature. As solvents there come into consideration especially aromatic hydrocarbons such as benzene, toluene or xylene, chlorinated hydrocarbons such as methylene chloride or chloroform, ethers such as diethyl ether, tetrahydrofuran or dioxan, and the like. The reaction is effected under reaction conditions which are usual in peptide chemistry, i.e. preferably in the presence of a condensation agent such as HBTU (O-benzo5 triazolyl-N.N.N*.N'-Letramethyluroniura hexafluorophosphate), BOP (benzotriazol-l-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate). BOPC (bis(2-oxo-2-oxozolidinyl)phosphine chloride). HOBT (N-hydroxybenzotriazole). DBU (1.8-diazabicyclo[5.4.O]-undec-7-ene). DCC (di10 cyclohexylcarbodiimide). EDC (N-ethyl-N'(3-dimethylaminopropyl)carbodiimide hydrochloride). Htinig base (ethyldiisopropylamine). and the like. The reaction is conveniently carried out in an organic solvent or solvent mixture which is inert under the reaction conditions at a temperat.ure between about OeC and 50°C. preferably at about room temperature. As solvents there come into consideration especially dimethylformamide, methylene chloride, acetonitrile. tetrahydrofuran, and the like.

The starting materials of formula II in which R signifies group (a), wherein m signifies the number 3. or group (b) are novel and are also an object of the present invention. They can be prepared, for example, by cleaving off the amino protecting group and simultaneously also the O-protecting group in a compound of the general formulae wherein B sigifies an amino protecting group, prefer35 ably t-butoxycarbonyl or benzyloxycarbonyl. and R . and n have the significance given above. - 8 The cleavage of the N-protecting group and ©-protecting group is also effected according to methods known per se, for example in an organic solvent or solvent mixture which is inert under the reaction conditions at a temperature between about 0°C and room temperature using an acid such as hydrochloric acid, trifluoroacetic acid, and the like. Suitable solvents are ethers such as tetrahydrofuran or dioxan, alcohols such as methanol or chlorinated hydrocarbons such as methylene chloride, and the like. Under these reaction conditions the oxazolidine ring is. as already mentioned, simultaneously cleaved.

The starting materials of formula II in which R signifies group (a), wherein m signifies the number 2, are known or can be obtained in analogy to the preparation of the known compounds.

The compounds of formulae IV and V are also novel and are objects of the present invention. They can be prepared according to different methods known per se starting from compounds of formula VI. These preparative procedures are compiled in Scheme I hereinafter. In this Scheme Met signifies a metal such as lithium or magnesium 6 ... and B. R . R and n have the significance as given above. With respect to the precise reaction conditions reference is made to the experimental section.

Scheme I - 10 The starting materials of formula III in which A, B and X each signify a nitrogen atom and Y signifies -CH- are known from EP-A 0.369.743 or can be obtained in analogy to the preparation of the known compounds.

The remaining compounds of formula III are also novel and are an object of the present invention. They can be prepared starting from corresponding pyrazinones. pyridaz inones and pyridinones according to various methods which are known per se and which are in part analogous to the process described in EP-A 0.369.743. These preparative procedures as well as the process according to EP-A 0.369.743 are compiled in Schemes II-IV hereinafter. In 2 these Schemes R signifies alkyl and A. B, R . R and R3 have the significance given above. The pyrazinones of formula XVI in Scheme TT and the pyridazinones of formula XXIV in Scheme III as well as their preparation 2o ate described in part in EPA 0.369.743 or Chim. Ther.. 6., 109 (1971) or can be obtained in analogy to the preparation of the known compounds. The pyridinones of formula XXXII in Scheme IV are novel, but belong to a known class of substance. They can be prepared in analogy to the preparation of the compounds described in Tetrahedron Letters 1974. 1183 and Arch. Pharm.. 317. 183 (1984). !ySh R,™ I - 11 Scheme II CN HN—NH, XIX ygl. EPA 0.369. 743 NH, •A R,XS / / COOR COOH COOR - 12 Scheme III COOR COOH Rirab COOR - 13 Scheme IV XXXIII III c COOR COOR - 14 The compounds of formula 1 and their pharmaceutically usable salts have an inhibitory activity on the natural enzyme renin. The latter passes from the kidneys into the blood and there brings about the cleavage of angiotensinogen with the formation of the decapeptide angiotensin 1 which is then cleaved in the lungs, the kidneys and other organs to the octapeptide angiotensin II. Angiotensin II increases the blood pressure not only directly by arterial constriction, but also indirectly by the liberation of the sodium ion-retaining hormone aldosterone from the adrenal gland, with which is associated an increase in the extracellular fluid volume. This increase is attributed to the action of angiotensin II itself or to the heptapeptide angiotensin 111 which is formed therefrom ae a cleavage product. Inhibition of the enzymatic activity of renin brings about a decrease in the formation of angiotensin I and as a consequence thereof the formation of a smaller 2q amount of angiotensin II. The reduced concentration of this active peptide hormone is the actual reason for the blood pressure-lowering activity of renin inhibitors.

The activity of renin inhibitors can be demonstrated experimentally by means of the in vitro test described hereinafter: In vitro test with pure human renin The test is carried out in Eppendorf test tubes. The 3Q incubation mixture consists of (1) 100 μΐ of human renin in buffer A (0.1M sodium phosphate solution, pH 7.4. containing 0.1* bovine serum albumin. 0.1* sodium azide and 1 mM ethylenediaminetetraacetic acid), sufficient for a renin activity of 2-3 ng of angiotensin I/ml/hr.; (2) 35 145 μΐ of buffer A; (3) 30 μΐ of 10 μΜ human tetradecapeptide renin substrate (hTD) in 10 mM hydrochloric acid; (4) 15 μΐ of dimethyl sulphoxide with or without inhibitor and (5) 10 μΐ of a 0.03 molar solution of - 15 hydroxyquinoline sulphate in water.

The samples are incubated for three hours at 37°C or 4°C in triplicate. 2 x 100 μΐ samples per experimental test tube are used in order to measure the production of angiotensin I via RIA (standard radioimmunoassay; clinical assay solid phase kit). Cross reactivities of the antibody IQ used in the RIA are: angiotensin 1 100%; angiotensin II 0.0013%; hTD (angiotensin I-Val-Ile-His-Ser-OH) 0.09%. The production of angiotensin I is determined by the difference between the experiment at 37°c and that at 4°c.

The following controls are carried out: (a) Incubation of hTD eamples without renin and without inhibitor at 37eC and 4®C. The difference between these two values gives the base value of the angiotensin I 20 production. (b) Incubation of hTD samples with renin, but without inhibitor at 37°C and 4°C. The difference between these values gives the maximal value of angiotensin I production In each sample the base value of the angiotensin I production is subtracted from the angiotensin I production which is determined. The difference between the maximal value and the base value gives the value of the maximal substrate hydrolysis ( 100%) by renin.

The results are given as ΙΟ^θ values which denote that concentration of the inhibitor at which the enzymatic activity is inhibited by 50%. The IC__ values are deterbO mined from a linear regression curve from a logit-log plot The results obtained in this test are compiled in the following Table: Compound - 16 Table IC_ value in nmol/lt 50 A 61 B 43 C 42 D 57 E 48 F A = (R or S)-N-[(IS,2R,3S)-1-(Cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl]-8-propyl-a,6-bis(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide.

B = (R or S)-N-[(IS.2R,3S)-1-(Cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-isopropyl-a-(imidazol-4 -ylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]-pyrazine-3 -acetamide.

C = (R or S)-N-[(1S.2R,3S)-1-(Cyclohexylmethyl)-3-cyclohexyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylraethyl)-8-isobutyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate.

D = (R or S)-N-[(lS.2R.3S)-l-(Cyclohexylmethyl)-2.3-dihydroxy-5-methylhexyl]-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetamide E = (S or R)-N-[(lS.2R,3S)-l-(Cyclohexylraethyl)-3-cyclopropy1-2,3-dihydroxypropylJ-8-[(RS)-l-methylpropylj-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a ] pyrazine-3-acetamide. - 17 F = N-[(lS,2R,3S)-l-(Cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl] - 8- [(RS)-1-methylpropyl]-6-(3-pyridyl) s-triazolo[4,3-a]pyrazine-3-carboxamide.

The compounds of formula I as well as their pharmaceutically usable salts can be used as medicaments, e.g. in the form of pharmaceutical preparations. The pharmaceutical preparations can be administered enterally such as orally, e.g. in the form of tablets, coated tablets, dragees, hard and soft gelatine capsules, solutions, emulsions or suspensions, nasally, e.g. in the form of nasal sprays, or rectally. e.g. in the form of suppositories. However, the administration can also be effected parenterally such as intramuscularly or intravenously, e.g. in the form of injection solutions.

For the manufacture of tablets, coated tablets, dragees and hard gelatine capsules the compounds of formula I as well as their pharmaceutically usable salts can be processed with pharmaceutically inert, inorganic or organic excipients. Lactose, maize starch or derivatives thereof, talc, stearic acid or its salts etc can be used as such excipients for e.g. tablets, dragees and hard gelatine capsules.

Suitable excipients for soft gelatine capsules are e.g. vegetable oils, waxes, fats, semi-solid and liquid polyols etc.

Suitable excipients for the manufacture of solutions and syrups are e.g. water, polyols, saccharose, invert sugar, glucose etc.

Suitable excipients for injection solutions are e.g. water, alcohols, polyols, glycerol, vegetable oils etc. - 18 -Suitable excipients for suppositories are e.g. natural or hardened oils, waxes, fats, semi-liquid or liquid polyols etc.

Moreover, the pharmaceutical preparations can contain preserving agents, solubilizers, viscosity-increasing substances, stabilizing agents, wetting agents, emulsi10 tying agents, sweetening agents, colouring agents. flavouring agents, salts for varying the osmotic pressure, buffers, coating agents or antioxidants. They can also contain other therapeutically valuable substances.

In accordance with the invention the compounds of general formula I as well as their pharmaceutically usable salts can be used in the control or prevention of high blood pressure and cardiac insufficiency. The dosage can vary within wide limits and will, of course, be fitted to 2o the individual requirements in each particular case. In general, in the case of oral administration there ehould suffice a daily dosage of about 3 mg to about 3 g. preferably about 10 mg to about 1 g. e.g. approximately 300 mg per person, divided in preferably 1-3 unit doses, which can e.g. be of the same amount, whereby, however, the upper limit just given can also be exceeded when this is found to be indicated. Usually, children receive half of the adult dosage.

The following Examples are intended to illustrate the present invention, but are not intended to be limiting in any manner. All temperatures are given in degrees Celsius.

Example 1 218 mg (0.56 mmol) of rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid. 127 mg (0.56 mmol) of (IS.2R.3S)-3-amino-4-cycloIE 912254 - 19 -hexyl-l-cyclopropyl-1.2-butanediol (EP-A 0.332.008) and 248 mg of (0.56 mmol) of benzotriazol-l-yloxy-tris-(di5 methylamino)phosphonium hexafluorophosphate (BOP) are dissolved in 20 ml of methylene chloride (CH2C12). 0.192 ml (1.12 mmol) of HUnig base is added thereto and the solution is stirred at room temperature for 12 hours. Subsequently, it is partitioned between CH2C12 and Xq saturated ammonium chloride solution, the organic phase is dried over sodium sulphate and finally the solvent is removed under reduced pressure.

The crude product (600 mg of yellow oil), which con25 tains the desired product as a 1:1 mixture of two epimere, is purified and separated into the two epimers by chromatography on silica gel using a 10:1 mixture of CH2C12 and methanol. There are thus obtained 33 mg (10*) of the more polar epimer (R or S)-N-[(1S.2R,3S)-1-(cyclohexyl2o methyl)-3-cyclopropyl-2.3-dihydroxylpropyl]-8-propyl-a,6-bis(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide as yellow crystals, MS: 598 (M4H)+. 76 mg (22.7*) of the pure, less polar epimer (S or R)-N-[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihyroxypropyl]-8-propyl-a,6-bis (3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acet25 . + amide. MS: 598 (M+H) , and 166 mg (49.6*) of a mixture of both epimers, i.e. (RS)-N-[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-a.6-bis(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide. MS : 3Q 598 (M+H)+.

The rac-8-propyl-6-(3-pyr idyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid used as the starting material was prepared as follows: 3.31 g (11.7 mmol) of 3-(2-ammo-l.l-diethoxyethyl)pyridine [Org. Synthesis 64, 19(1986)] and 1.17 ml (11.7 mmol) of 2-oxo-n-valeric acid are dissolved in - 20 150 ml of dimethylformamide. 2.63 ml (23.4 mmol) of N-methylmorpholine and 4.85 g (12.8 mmol) of TBTU [2-(lH5 -benzotriazol-l-yl)-l,1.3.3-tetramethyluronium tetrafluoroborate] are added thereto and the solution is stirred at room temperature under argon for 14 hours. The mixture is partitioned between ethyl acetate and water and there are obtained, after the usual working-up of the 2Q organic phase. 2.6 g of crude product as a brown oil which is purified by chromatography on silica gel (eluent: 95:5 mixture of CH2C12 and ether, yield: 1.42 g (39%) of N-[2.2-diethoxy-2-(3-pyridyl)ethyl]-2-oxovaleramide. MS: 309 (M+H)+. 500 mg (1.62 mmol) of N-[2.2-diethoxy-2-(3-pyridyl)ethyl]-2-oxovaleramide are treated with 20 ml of 2N hydrochloric acid and subsequently etirred at 30° for hour6. Thereafter the solvent is removed in a high 20 vacuum and the residue is treated twice with toluene, which is again removed each time under reduced pressure.

The desired product is thus obtained as beige crystals, yield: 420 mg (95%). Recrystallization from methanol/ether yields N-(nicotinoylmethyl)-2-oxo-valera25 . . . mide. melting point 80-82°. 150 mg (0.55 mmol) of N-(nicotinoylmethyl)-2-oxovaleramide and 1.5 g (19.3 mmol) of ammonium acetate are dissolved in 10 ml of ethanol and the solution is heated to reflux for 90 minutes. Then, the mixture is poured on to 50 ml of ice/water. extracted three times with 20 ml of ethyl acetate each time, the organic phase is washed with 30 ml of water, dried over sodium sulphate and the solvent is then removed under reduced pressure, crude yield: 195 mg of yellow crystals. Recrystallization from ethyl acetate yields 3-propyl-5-(3-pyridyl)-2(lH)-pyrazinedione. melting point 188-189° (dec.). - 21 430 mg (2 mmol) of 3-propyl-5-(3-pyridyl)-2(lH)-pyrazinedione are treated with 2 ml of phosphorus oxychloride and the mixture is subsequently heated to reflux for 5 hours. Then, the phosphorus oxychloride is removed under reduced pressure, the residue is evaporated once with toluene and the crude product is dissolved in 20 ml of CH^Cl^ and washed with 10 ml of ice-water. The aqueous phase is extracted once with 10 ml of CH2C12 and the combined organic phases are dried over sodium sulphate. The solvent is removed under reduced pressure and the desired 2-chloro-3-propyl-5-(3-pyridyl)pyrazine is obtained as beige crystals, yield: 468 mg (36%); melting 15 point 207-209° (from CH2Cl2/ether). 2.5 ml of pyridine are treated with 2.5 ml (51.4 mmol) of hydrazine hydrate. 500 mg (1.85 mmol) of 2-chloro-3-propyl-5-(3-pyridyl)pyrazine are added thereto and the 2θ mixture is subsequently heated to reflux for 90 minutes. Thereafter, the reaction solution is left to cool. 10 ml of water are added, the mixture is cooled at 5° for 30 minutes and finally the crystallized-out product is filtered off under suction.

The crude product is dried over potassium hydroxide at 40° under reduced pressure and recrystallized from alcohol/water (1:1). whereby there are obtained 270 mg (63.6%) of 2-hydrazino-3-propyl-5-(3-pyridyl)pyrazine as beige needles, melting point 162-163°. 340 mg (1.35 mmol) of diethyl (3-pyridyl)malonate (Arch. Pharm. 308. (1975) 663). 311 mg (1.35 mmol) of 2-hydrazino-3-propyl-5-(3-pyridyl)pyrazine and 257 mg (1.35 mmol) of p-toluenesulphonic acid are treated with 150 ml of xylene and the mixture is subsequently heated to reflux on a water separator for 12 hours. Thereafter, the xylene is distilled off, the residue is dissolved in - 22 CH^Cl^. washed with sodium bicarbonate solution, the organic phase is dried over sodium sulphate and the solvent is removed under reduced pressure. The residue is chromatographed on silica gel using a 10:1 mixture of CH2C12 and methanol, whereby there are obtained 300 mg (53%) of ethyl rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetate. MS: 416 (M)+. 300 mg (0.72 mmol) of ethyl rac-8-propyl-6-(3-pyridyl )-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetate are dissolved in 50 ml of ethanol, treated with 15 1.44 ml of IN sodium hydroxide solution (1.44 mmol) and the solution is subsequently heated at 50° for 2 hours.

It is neutralized by adding 1.44 ml of IN hydrochloric acid (pH 5) and evaporated to dryness under reduced pressure. The residue ie then partitioned between water 20 (5 ml) and a 10:1 mixture of CH2C12 and methanol (50 ml). The organic phase is dried over sodium sulphate and the solvent is removed under reduced pressure. There are thus obtained 300 mg (53%) of rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid as a yellow amorphous powder, R_:0.1 F (CH2Cl2/MeOH: 5:1).

Example 2 The following compounds were manufactured in an analogous manner to that described in Example 1: From rac-α-(imidazol-4-ylmethyl)-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R,3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the two epimers (R or S)-N-[(IS,2R.3S)-1-(cyclohexylmethyl )-3-cyclopr opyl-2. 3-d ihydroxypropyl] -a- ( imidazo 1-4-ylmethyl-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazineIE 912254 - 23 -3-acetamide and (R or S)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-a-(imidazol-45 -ylmethy1)-8-propyl-6-(3-pyridyl)-a-triazolo[4.3-a]-pyrazine -3-acetamide, each as a pale yellow solid, MS: 587 (M+H)*; from 8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine10 -3-acetic acid and (1S.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the N-[(lS,2R.3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide as a solid. MS: 507 (M+H)+; from rac-8-isopropyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R,3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the (RS)-N-[(1S.2R,3S)-l-(cyclohexylmethyl)-3-cyclo20 pr opyl-2.3-d ihydroxypropy 1)-8-isopropyl-6-(3-pyr idyl )-+; from rac-8-i6opropyl-a-(imidazol-l-ylmethyl)-6-(325 -pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the two epimers (S or R)-N-[(IS.2R.3S)-1-(cyclohexylmethyl )-3-cyclopropy1-2.3-dihydroxypropy1)-8-isopropyl-a-(imidazol-4-ylmethy1)-6-(3-pyridyl)-s-triazolo[4.3-a)3q -pyrazine-3-acetamide and (R or S)-N-[(1S.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2,3-dihydroxypropyl)-8-isopropyla-(imidazol-4-ylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]-pyrazine-3-acetamide. each as a pale yellow solid, MS: 587 (M+H)+; from rac-B-isobutyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropy1-1,2-butanediol - 24 the 3:l-epimer mixture (RS)-N-[(1S.2R,3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl]-8-isobutyl-a5 -(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolot4,3-a]pyrazine-3-acetamide and the les6 polar, pure epimer (5 or R)-N-[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-isobutyl-α-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide. each as a pale yellow solid. MS: 612 (M+H)+; from rac-8-isobutyl-a-(imidazol-l-ylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R,3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the two epimers (S or R)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclohexyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-8-isobutyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate and (R or S)-N-[(IS.2R,3S)-1-(cyclohexylmethyl )-3-cyclohexyl-2. 3-d ihydroxypropyl] -a- (imidazol-42o -ylmethyl)-8-isobutyl-6-(3-pyridyl)-s-tri azolot4.3-a]pyrazine-3-acetate, each as a solid. MS: 601 (M+H)+; from 8-isobutyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l25 -cyclopropyl-1.2-butanediol theN-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-isobutyl-6-(3-pyridyl)-s-triazolof4.3-a]pyrazine-3-acetamide as a solid, MS: 521 (M+H)+: - from rac-6-(4-pyridyl)-a-(3-pyridylmethyl)-8-propyl-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l,2-butanediol the 1:1 epimer mixture (RS)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl]-8-propyl-6-(4-pyridyl)... -a- (3-pyr idylmethyl )-s-tr iazolo [ 4.3-a]pyrazine-3-acetamide as a solid. MS: 598 (M+H) ; from rac-α-(imidazol-4-ylmethyl)-8-propyl-6-(4IE 912254 - 25 -pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butane5 diol the (RS)-N-[(lS.2R,3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-8-propyl-6-(4-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide as a 1:1 epimer mixture, MS: 587 (M+H)+; - from 8-propyl-6-(4-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS,2R,3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the N-[(IS.2R.3S)-1-(cyclohexylmethy1)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propy1-6-(4-pyridyl)-s-triazolo[4,3-a]pyrazine-3-carboxamide as a pale yellow solid. MS: 507 (M+H)+; from 6-phenyl-8-propyl-s-triazolo[4,3-b]-pyridazine-3-acetic acid and (1S.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the N-[(IS,2R.3S)-1-(cyclohexyl2Q methyl)-3-cyclopropyl-2,3-dihydroxypropyl]-6-phenyl-8-propyl-s-triazolo[4.3-b]pyridazine-3-acetamide as a solid, MS: 508 (M+H)+; from rac-6-phenyl-8-propyl-a-(3-pyridylmethyl)-s-triazolo[4.3-b]pyridazine-3-acetic acid and (1S.2R.3S)25 -3-amino-4-cyclohexyl-l-cyclopropy1-1.2-butanediol the (RS)-N-[(IS.2R,3S)-1-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-6-phenyl-8-propyl-a-(3-pyridylmethyl)-s-triazolo[4.3-b]pyridazine-3-carboxamide as a solid.

MS:598 (M+H)+; from 8-benzyl-6-phenyl-s-triazolo[4.3-b]pyridazine-3-acetic acid and (1S.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the 8-benzyl-N-[(IS,2R.3S)-1-(cyclohexylmethyl )-3-cyclopropy1-2.3-dihydroxypropyl]-6-phenyl-s35 . . -tnazolo[4.3-b]pyridazine-3-acetamide. MS: 482 (M-C4H?O)+; - 26 from (RS)-8-benzyl-6-phenyl-a-(3-pyridylmethyl)-s-triazolo[4.3-b]pyridazine-3-acetic acid and (IS,2R,3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l,2-butanediol the (RS)-8-benzyl-N-[(1S,2R.3S)-1-(cyclohexylmethyl)-35 -cyclopropyl-2.3-dihydroxypropyl]-6-phenyl-a-(3-pyridylmethyl)-s-triazolo[4,3-b]pyridazine-3-acetamide, MS: 645 (M+H)+; from rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)10 -s-triazolo[4.3-a]pyrazine-3-acetic acid and (2S.3R.4S)-2-amino-1-cyclohexy1-6-methyl-3,4-heptanediol (J.Med.Chem. 31 (12), 2277, 1988) the two epimers (S or R)-N-((IS.2R,3S)-1-( eyelohexyImethyl)-2,3-dihydroxy-5-methy1hexyl]-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s15 -triazolo(4.3-a]pyrazine-3-acetamide and (R or S)-N-[(lS.2R.3S)-l-(eyelohexyImethyl)-2.3-dihydroxy-5-methylhexy1)-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetamide. MS: in each case 614 (M+H)+; from rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid and (1S.2R,3S)-3-amino-l-cyclopropyl-4-phenyl-l.2-butanediol the 1:1 epimer mixture (RS)-N-[(lS,2R.3S)-l-(cyclohexylmethyl)-325 -cyclopropyl-2.3-dihydroxypropyl]-8-propyl-a-(3-pyr idyl-methyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide.MS: 592 (M+H) + ; from rac-8-benzyl-6-(3-pyridyl)-a-(3-pyridylmethyl) 30 -s-triazolo[4,3-a]pyrazine-3-acetic acid and (IS,2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the 1:1 epimer mixture (RS)-8-benzyl-N-[(lS,2R,3S)-l-(cyclohexyImethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]-pyrazine35 -3-acetamide. MS: 646 (M+H)+; - 27 from rac-8-benzyl-a-(imidazol-4-ylmethyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropy1-1.2-butanediol the 1:1 epimer mixture (RS)-8-benzyl-N-[(IS,2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide. MS: 635 (M+H)+; from 8-benzyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the 8-benzyl-N-[(lS.2R,3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-6-(315 -pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide as a solid. MS: 555 (M+H)+; from rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-6-triazolo[4.3-a]pyrazine-3-acetic acid and (2S,3R.4S)-22q -amino-l-cyclohexyl-5-methyl-3.4-hexanediol (EP-A 0.332.008) the two epimers (R or S)-N-[(1S.2R.3S)-1-(cyclohexylmethyl)-2,3-dihydroxy-4-methylpentyl]-8-oxopropyl-6-(3-pyridyl)-a-(3-pyridylmethy1)-s-triazolo-[4,3-a]pyrazine-3-acetamide and (S or R)-N-[(IS,2R.3S)-1-(cyclohexylmethyl)-2.3-dihydroxy-4-methy1pentyl]-8-oxo25 propyl-6-(3-pyridyl)-a-(3-pyridylmethy1)-s-triazolo[4.3-a]pyrazine-3-acetamide. MS: in each case 600 (M+H)+; from rac-α-(imidazol-4-ylmethy1)-8-propyl-6-(33Q -pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-l-eyelopropyl-4-pheny1-1,2-butanediol the 2:1 epimer mixture (RS)-N-[(IS,2R.3S)-1-(cyclohexylmethyl )-3-cyclopropyl- 2. 3-d ihydroxypropyl] -a- ( imidazol-4-ylmethyl)-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide as a solid. MS: 580 (M) + ; from rac-α-(imidazol-4-ylmethyl)-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and - 28 (2S.3R,4S)-2-amino-l-cyclohexyl-6-methy1-3,4-heptanedio1 the two epimers (R or S)-N-f(IS.2R.3S)-1-(cyclohexyl5 methyl)-2.3-dihydroxy-4-methylhexyl]-a-(imidazol-4-ylmethyl)-8-propy1-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide and (S or R)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-2.3-dihydroxy-4-methylhexyl]-a-(imidazol-4-ylmethyl)-8-propyl-6-(3-pyridyl)-s-triazolot4.3-a]pyrazine-310 -acetamide. MS: in each case 603 (M+H)+; from rac-α-(imidazol-4-ylroethyl)-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (2S.3R.4S)-2-amino-l-cyclohexyl-5-methy1-3.4-hexanediol the two epimers (R or S)-N-t(lS.2R.3S)-l-(cyclohexylmethyl)-2.3-dihydroxy-4-methylpentyl]-a-(imidazol-4-yImethyl)-8-propy1-6-(3-pyridyl)-6-triazolot4,3-a]pyrazine-3-acetamide and (S or R)-N-f(lS.2R.3S)-l-(cyclohexylmethyl)-2,3-dihydroxy-4-methylpentyl]-a-(imidazo1-42q -ylmethyl)-8-propyl-6-(3-pyridyl)-s-triazolof4.3-a]pyrazine -3-acetamide. MS: in each case 589 (M+H)+; from rac-8-propyl-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo(4.3-b]pyridazine-3-acetic acid and (1S.2R.3S)25 -3-amino-4-cyclohexyl-l-cyclopropyl-l,2-butanediol the (RS)-N-[(1S.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo(4.3-b]pyridazine-3-acetamide as a 1:1 epimer mixture, MS: 598 (M+H)+; from rac-8-propyl-a-(3-pyridylmethyl)-6-(2-thienyl)-6-triazolo(4.3-b]pyridazine-3-acetic acid and (1S.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-l.2-butanediol the two epimers (S or R)-N-t(IS.2R.3S)-1-(cyclohexylmethyl)-355 -eyelopropyl-2.3-d ihydroxypropyl]-8-propy1-a-(3-pyridylmethyl )-6-(2-thienyl)-s-triazo lot 4. 3-b]pyridazine-3-acetamide and (R or S)-N-t(IS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propy1-a-(3IE 912254 - 29 -pyridylmethyl)-6-(2-thienyl)-6-triazolo[4.3-b]-pyridazine-3-acetamide. each as a solid. MS: 603 (M+H)*: from 8-propyl-6-(2-thienyl)-s-triazolo[4.3-b]-pyridazine-3-acetic acid and (1S.2R.3S)-3-amino-4-cyclohexyl-1-cyclopropyl-l.2-butanediol the N-[(IS.2R,3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-610 -(2-thienyl)-s-triazolo[4.3-b]pyridazine-3-acetamide as a solid. MS: 511 (M)+; from rac-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IR or S.2R or S)-l-[(lR.2S)-l-amino-3-cyclohexyl-l-hydroxypropyl]-1.2-cyclohexanediol the two epimers (R or S)-N-[(IS.2R)-1-(cyclohexylmethyl)-2-hydroxy-2-[(IR or S.2R or S)-1.2-dihydroxyphenyl]ethyl]-8-propyl-a-(3-pyridylmethyl)-8-propyl-s-triazolo(4,3-a]pyrazine-3-acetamide and (S or R)-N-[(IS.2R)-1-(cyclohexylmethyl)-2-hydroxy-2-[(IR or S.2R or S)-l.2-dihydroxyphenylJethyl)-8-propyl-a-(3-pyridylmethyl)-8-propyl-s-triazolo[4,3-a]pyrazine-3-acetamide. each as a solid. MS: 642 (M+H)*; - from (RS)-8-[(RS)-l-methylpropyl]-a-(3-pyridylmethy1)-6-(3-pyridyl)-6-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the two epimer mixtures (S or R)-N-[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-8-[(RS)-l-methylpropyl]-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide and (RS)-N-[(IS.2R,3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-[(RS)-l-methylpropyl]-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-335 -acetamide, each as a pale yellow solid, MS: 612 (M+H)*; from rac-8-(l-methylpropyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid and (lS.2R.3S)-3-amino-4IE 912254 - 30 -cyclohexyl-l-cyclopropyl-1.2-butanediol the N-[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-di5 hydroxypropyl]-8-[(RS)-1-methylpropyl]-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-carboxamide as a solid. MS: 520. (M)+. from rac-15 methy1)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide and (R or S)-8-[(RS)-l-methylpropyl]-N-[(1S.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-6-(3-pyridyl)-ε-triazolo[4.3-a]pyrazine-3-acetamide, each as a pale yellow solid, MS: 601 (M+H>+: from rac-a-methyl-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexyl-l-cyclopropyl-1.2-butanediol the (RS)-N-[(IS.2R.3S)-1-(eyelohexyImethyl)-3-cyclopropyl-2.3-di25 hydroxypropyl]-a-methyl-8-propyl-6-(3-pyridyl)-s-trlazolo[4.3-a]pyrazine-3-acetamide as a 1:1 epimer mixture.

MS: 521 (M+H)+; and - from rac-a-methyl-8-[(RS)-l-methylpropyl]-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid and (IS.2R.3S)-3-amino-4-cyclohexy1-1-cyclopropyl-1.2-butanediol the (RS)-8-((RS)-l-methylpropyl]-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-a-methyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide 35 . . + ae a mixture of diastereomers, MS: 535 (M+H) .

The acids and amine diols used as the starting - 31 materials were prepared as follows: rac-a-(Imi dazol-4-ylmethy1)-8-propyl-6-(3-pyridyl)-s-triazolof4.3-a 1pyrazine-3-acetic acid In an analogous manner to that described in Example 1, by condensing 2-hydrazino-3-propyl-5-(3-pyridyl)pyrazine with diethyl (imidazol-4-yl-methyl)malonate (J.Chem.Soc. 99. (1911) 1390) there is obtained ethyl rac-α-(imidazol-4-ylmethy1)-8-propyl-6-(3-pyridyl)-s-triazolof 4.3-a]pyrazine-3-acetate, MS: 405 (M)+. which is converted into the above acid by saponification analogously to 15 Example 1. 8-Propyl-6-(3-pyridyl)-s-triazolof 4.3-a]pyrazine-3-acetic acid 2θ In an analogous manner to that described in Example 1, by condensing 2-hydrazino-3 propyl-5-(3-pyridyl)pyrazine with diethyl malonate in toluene in place of xylene there is obtained ethyl 8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate, MS: 325 (M)+. and by corresponding basic saponification there is obtained the . . + desired acid. MS: 269 (M-C2H4) . rac-8-Isopropyl-6-(3-pyridyl)-a-(3-pyr idylmethyl)-s-triaζο!οΓ4.3-a1pyrazine-3-acetic acid In an analogous manner to Example 1. by condensing 3-(2-amino-l,1-diethoxyethyl)pyridine with 3-methyl-2-oxobutanoic acid there is obtained N-[2,2-diethoxy-2-(3-pyridyl)ethyl]-3.3-dimethyl-2-oxobutyramide. Acidic hydrolysis to 3-methyl-N-(nicotinoylmethyl)-2-oxobutyramide and . . . . subsequent ring closure gives 3-isopropyl-5-(3-pyndyl)-2(1H)-pyrazίnone as a yellow, crystalline solid, melting point 200-202° (from ethyl acetate). The conversion into - 32 the corresponding chloride. 2-chloro-3-isopropyl-5-(3-pyridyl)pyrazine, is effected analogously to Example 1.

Hydrazinolysis yields 2-hydrazino-3-isopropyl-5-(35 -pyridyl)pyrazine as beige crystals, melting point 164-165° (from ethanol/water), and subsequent condensation with diethyl (3-pyridyl)malonate yields ethyl rac-8-isopropy1-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetate as a pale yellow solid. MS: 416 (M)+. which is converted into the above acid by basic saponification. rac-8-Isopropyl-g-(imidazol-4-ylmethyl)-6-(3-pyridyl) - s-triazoloH, 3-alpyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 2- hydrazino-3-isopropyl-5-(3-pyridyl)pyrazine with diethyl (imidazol-4-ylmethylJmalonate there is obtained ethyl rac-8-isopropyl-a-(imidazol-4-ylmethyl)-6-(3-pyridyl)-s20 -triazolo[4,3-a]pyrazine-3-acetate. MS: 405 (M)+. which is converted into the above acid by alkaline saponification. rac-8-Isobutyl-g-(3-pyridylmethyl)-6-(3-pyridyl)-s25 -triazolor4,3-a1pyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 3- (2-amino-l.1-diethoxyethyl)pyridine with 4-methyl-2-oxopentanoic acid there is obtained N-(2,2-diethoxy-2-(330 -pyridyl)ethyl]-4-methyl-2-oxovaleramide as a colourless, amorphous solid. Acidic hydrolysis yields 4-raethyl-N-(nicotinoylmethyl)-2-oxovaleramide and subsequent ring closure yields 3-isobutyl-5-(3-pyridyl)-2(lH)-pyrazinone as a crystalline solid, melting point 195-196° (from ethyl acetate). The conversion into the corresponding chloride. 2-chloro-3-isobutyl-5-(3-pyridyl)pyrazine, is also - 33 effected analogously to Example 1.

Hydrazinolysis of the chloride yields 2-hydrazino-3-isobutyl-5-(3-pyridyl)pyrazine as beige crystals, melting point 154-155° (from ethanol/water) and subsequent condensation with diethyl (3-pyridyl)malonate yields ethyl rac-8-isobutyl-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 430 (M)+, which is converted into the above acid by basic saponification. rac-α-(Imidazo1-4-ylmethy1)-8-isobutyl-6-(3-pyridyl)-s-triazoloH, 3-alpyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 215 -hydrazino-3-isobutyl-5-(3-pyridyl)pyrazine with diethyl (imidazol-4-ylmethyl)malonate there is obtained ethyl rac-a-(imidazo1-4-ylmethyl)-8-isobuty1-6-(3-pyridyl)-s-triazolo[4.3-s]pyrazine-3-acetate, MS: 419 (M)+. which is converted into the above acid by alkaline saponi20 fication. 8-Isobutyl-6-(3-pyridyl)-s-triazolor4.3-s]pyrazine-3-acetic acid In an analogous manner to Example 1. by condensing 2- hydrazino-3-isobutyl-5-(3-pyridyl)pyrazine with diethyl malonate there is obtained ethyl 8-isobutyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 339 (M)+. which is converted by saponification into the above acid: MS 267 (M-CO2)+. rac-8-Benzyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4,3-a1pyrazine-3-acetic acid In an analogous manner to Example 1. by condensing 3- (2-amino-l.1-diethoxyethyl)pyridine with phenylpyruvic - 34 acid there is obtained N-[2,2-diethoxy-2-(3-pyridyl)ethyl]-3-phenylpyruvamide as an amorphous, yellow solid. Subsequent acidic hydrolysis to 3-phenyl-N-[[(3-pyridyl)carbonylJmethylJpyruvamide and ring closure gives 35 -benzyl-5-(3-pyridyl)-2(1H)-pyrazinone as a solid, melting point 188-190° (from ethyl acetate).

Chlorination to 2-benzyl-3-chloro-6-(3-pyridyl)pyrazine and hydrazinolysis yields 2-benzyl-3-hydrazino-610 -(3-pyridyl)pyrazine as a beige, crystalline solid.

Melting point 183-184° (from methanol/water).

Condensation with diethyl (3-pyridyl)malonate finally gives ethyl rac-8-benzyl-a-(3-pyridylmethyl)-6-(315 -pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate, MS: 464 (M)+. which is converted into the above acid by basic saponification. rac-8-Benzy1-a-(imidazo1-4-ylmethyl)-6-(3-pyridyl)-s20 -triazolof4.3-a1pyrazine-3-acetic acid In an analogous manner to that described in Example 1. by condensing 2-benzyl-3-hydrazino-6-(3-pyridyl)pyrazine with diethyl (imidazol-4-ylmethyl)malonate there is obtained ethyl rac-8-benzyl-a-(imidazol-4-ylmethyl)-6- (3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 453 (M)+. which is converted into the above acid by alkaline saponification. 8-Benzy1-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 2-benzyl-3-hydrazino-6-(3-pyridyl)pyrazine with diethyl malonate there is obtained ethyl 8-benzyl-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate, which is converted by - 35 basic saponification into the above acid, MS: 301 (M-CO2)+. rac-6-(4-Pyridyl)-a-(3-pyridyl)-8-propyl-s-triazolo5 [4.3-a]pyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 4-(2-amino-l.l-diethoxyethyl)pyrimidine [Org. Synthesis 64. 19 (1986)] with 2-oxopentanoic acid there is obtained N-[2.2-diethoxy-2-(4-pyridyl)ethyl]-2-oxovaleramide as a white solid, melting point 95-96°. Subsequent acidic hydrolysis to N-(isonicotinoylmethyl)-2-oxovaleramide and ring closure gives 3-propyl-5-(4-pyridyl)-2-pyrazinone as yellow crystals, melting point 237-238° (dec.).

Chlorination to 2-chloro-3-propyl-5-(4-pyridyl)-pyrazine and hydrazinolysis yields 2-hydrazino-3-propyl-5-(4-pyridyl)pyrazine as a red. crystalline solid, melting point 216-217’ (from ethanol/water).

Condensation with diethyl (3-pyridyl)malonate analogously to Example 1 finally gives ethyl rac-6-(4-pyridyl) -g-(3-pyridyl)-8-propyl-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 416 (M)+. which is converted into the above acid by basic saponification. rac-g-(Imidazol-4-ylmethyl)-8-propyl-6-(4-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetic acid Analogously to Example 1. by condensing 2-hydrazino-3 -propyl-5-(4-pyridyl)pyrazine with diethyl (imidazol-4-yl methyl)malonate there is obtained ethyl rac-g-(imidazol-4-ylmethy1)-8-propy1-6-(4-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate, MS: 405 (M)+. which is converted into the above acid by basic saponification. - 36 8-Propy1-6-(4-pyridyl)-s-triazoloΓ4,3-a1pyrazine-3-acetic acid Analogously to Example 1. by condensing 2-hydrazino-3-propyl-5-(4-pyridyl)pyrazine with diethyl malonate there is obtained ethyl 8-propyl-6-(4-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate, MS: 325 (M) + . which is converted into the above acid by basic saponification. 6-Phenyl-8-propyl-s-triazolof4.3-b]pyridazine-3-acetic acid In an analogous manner to Example 1. by chlorinating 15 6-phenyl-4-propyl-3(2H)-pyridazinone [Chim. Ther. 6, 109 (1971)] there is obtained 3-chloro-6-phenyl-4-propylpyridazine, MS: 232 (M)+, which is converted by hydrazinolysis into 3-hydrazino-6-phenyl-4-propylpyridazine, MS: 228 (M)+. Subsequent ring condensation with diethyl 2o malonate to ethyl 6-phenyl-8-propyl-s-triazolo[4.3-b]pyridazine-3-acetate. MS: 324 (M) + . followed by basic saponification gives the above acid as a solid, MS: 252 (M-CO2)+. rac-6-Phenyl-8-propy1-g-(3-pyridylmethyl)-s-triazoloΓ4.3-b]pyridazine-3-acetic acid In an analogous manner to Example 1. by condensing 3-hydrazino-6-phenyl-4-propylpyridazine with diethyl 30 (3-pyridyl)malonate there is obtained ethyl rac-6-phenyl-8-propyl-a-(3-pyridylmethyl)-s-triazolo[4.3-b]pyridazine-3-acetate. which is converted by basic saponification into the above acid. MS: 398 (M+H)+. 8-Benzyl-6-phenyl-s-triazoloΓ4.3-blpyridazine-3-acetic acid In an analogous manner to that described in Example 1, by the ring condensation of 4-benzyl-3-hydrazino-6-phenylIE 912254 - 37 pyridazine [Indian J.Chem., 15B. 352 (1977)] with diethyl malonate there is obtained ethyl 8-benzyl-6-phenyl-s-triazolo[4,3-b]pyridazine-3-acetate, MS: 372 (M)+, which is saponified with a base to the above acid, MS: 316 (M-CO)+.

(RS)-8-Benzyl-6-phenyl-g-(3-pyridylmethyl)-s-triazoloΓ4,3-b]pyridazine-3-acetic acid In an analogous manner, by the ring condensation of 4-benzyl-3-hydrazino-6-phenylpyridazine with diethyl (3-pyridyl)malonate there is obtained ethyl rac-8-benzyl-6-phenyl-a-(3-pyridylmethyl)-s-triazolo[4,3-b]pyridazine-3-acetate, which is converted by basic saponification into the above acid. MS: 436 (M+H)+. rac-8-(1-Methylpropyl )-6-(3-pyridyl)-s-triazolor4,3-a1pyrazine-3-acetic acid In an analogous manner to Example 1, by condensing 3-(2-amino-l,1-diethoxyethylJpyridine with 3-methyl-2-oxopentanoic acid there is obtained rac-N-[2.2-diethoxy-2-(3-pyridyl)ethyl]-3-methyl-2-oxovaleramide as an amorphous, colourless solid. Subsequent acidic hydrolysis to rac-325 -methyl-2-oxo-N-[(3-pyridylcarbony1)methyl]valeramide hydrochloride (beige, crystalline solid, melting point 158-159°) and ring closure gives rac-3-(l-methylpropyl)-5-(3-pyridyl)-2(lH)-pyrazinone as a yellow solid, melting point 146-148° (from acetonitrile). The conversion into rac-2-chloro-3-(l-methylpropyl)-5-(3-pyridyl)pyrazine is also effected analogously to Example 1. Hydrazinolysis to rac-2-hydrazino-3-(1-methylpropyl)-5-(3-pyridyl)pyrazine in the form of beige crystals, melting point 166-167° (from ethanol/water) and subsequent condensation with diethyl malonate gives ethyl rac-8-(1-methylpropyl)-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate. MS: 335 - 38 (M)+, which is converted by saponification into the above acid. MS: 267 (M-CC>2) + .

(RS)-8-Γ(RS)-l-Methylpropyll-g-(3-pyridylmethyl)-6-(35 -pyridyl)-s-triazolor4,3-a1pyrazine-3-acetic acid In an analogous manner to Example 1, by condensing rac-2-hydrazino-3-(1-methylpropyl)-5-(3-pyridyl)pyrazine with diethyl (3-pyridyl)malonate there is obtained ethyl (RS)-8-[(RS)-1-methylpropyl]-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 430 (M)+. which is converted into the above acid by alkaline saponification. rac-g-(lmidazol-4-yImethyl)-8-((RS)-1-methylpropyl]-6-(3-pyridyl)-s-triazolor4.3-a1pyrazine-3-acetic acid In an analogous manner to Example 1. by condensing rac-2-hydrazino-3-(l-methylpropyl)-5-(3-pyridyl)pyrazine with diethyl (imidazol-4-ylmethyl)malonate there is obtained ethyl (RS)-8-[(RS)-1-methylpropyl]-a-(imidazol-4-yImethyl)-6-(3-pyridyl)-s-triazolo(4,3-a]pyrazine-3-acetate, MS: 419 (M)+, which is converted into the above acid by alkaline saponification. 8-Propyl-6-(2-thienyl)-s-triazolor4.3-b]pyridazine-3-acetic acid 11.2 g (200 mmol) of potassium hydroxide in 75 ml of water are added at 0° dropwise to a suspension of 11.6 g (lOO mmol) of 2-oxo-n-valeric acid and 12.6 g (100 mmol) of 2-acetylthiophene in 75 ml of ethanol and the suspension is held at 0° for 48 hours. After evaporation of the ethanol the residue is made acid with 25% hydro35 chloric acid and extracted three times with ethyl acetate. The combined ethyl acetate extracts are dried. - 39 filtered and evaporated. After chromatography on silica gel using a 5:1 mixture of methylene chloride and methanol as the eluent and crystallisation from ether there are obtained 10.0 g (41%) of rac-a-hydroxy-a-propyl-γ5 -oxo-2-thiophenebutyric acid as a colourless powder, melting point 128-131°. MS: 197 (M-COOH)*.

A solution of 10 g of rac-a-hydroxy-a-propyl-γ-oxo-2-thiophenebutyric acid and 25 ml of hydrazine hydrate in 250 ml of ethanol is heated to reflux for hours. The solution is evaporated to about 40 ml and the separated crystals are filtered off under suction. There are thus obtained 5.1 g (56%) of 4-propyl-6-(2-thienyl)-3(2H)-pyridazinone as a colourless powder.

Melting point 171-174°, MS: 220 (M)+.

Chlorination to 3-chloro-4-propyl-6-(2-thienyl)pyridazine. MS: 238 (M)+. and hydrazinolysis yields 3-hydrazino-4-propyl-6-(2-thienyl)pyridazine. melting point 129-132°, analogously to Example 1.

Subsequent ring condensation with diethyl malonate yields ethyl 8-propyl-6-(2-thienyl)-s-triazolo[4,3-b]pyridazin-3-acetate. which is converted by basic saponi25 fication into the desired 8-propyl-6-(2-thienyl)-ε-triazolo [4,3-b]pyridazine-3-acetic acid. MS: 258 (M-CO2)+. rac-8-Propyl-a-(3-pyridylmethyl)-6-(2-thienyl)-s-triazoloΓ4.3-blpyridazine-3-acetic acid In an analogous manner to Example 1. by condensing the above-described 3-hydrazino-4-propyl-6-(2-thienyl)pyridazine with diethyl (3-pyridyl)malonate there is obtained ethyl rac-8-propyl-a-(3-pyridylmethyl)-6-(2-thienyl)35 -s-triazolo-[4.3-b]pyridazine-3-acetate. which is converted by alkaline saponification into the above acid, MS: 349 (M-CO2)+. - 40 rac-8-Propyl-ct- (3-pyridylmethyl )-6-( 3-pyridyl )-s-triazolo[4,3-b]pyridazine-3-acetic acid In an analogous manner to that described above, by an aldol condensation of 2-oxo-n-valeric acid with 3-acetylpyridine there is obtained γ-οχο-α-[(E)-propylidene]-3-pyridinebutyric acid, MS: 219 (M+H)+. Ring closure with hydrazine yields 4-propyl-6-(3-pyridyl)-3(2H)-pyridazinone. MS: 215 (M)+. which is converted into the corresponding chloride, 3-chloro-4-propyl-6-(3-pyridyl)pyridazine. MS: 233 (M) + . Hydrazinolysis to 3-hydrazino-4-propyl-6-(3-pyridyl)pyridazine. MS: 229 (M)+, and condensation with diethyl (3-pyridyl)malonate yields ethyl rac-8-propyl-g-(3-pyridylmethyl)-6-(3-pyri15 dyl)-s-triazolo[4,3-b]pyridazine-3-acetate. which is converted by basic saponification into the above acid. MS: 388 (M) + . rac-g-Methyl-8-propyl-6-(3-pyridyl)-s-triazolof4.3-a]20 pyrazine-3-acetic acid In an analogous manner to that described in Example 1. by condensing 2-hydrazino-3-propyl-5-(3-pyridyl)pyrazine with diethyl methylmalonate there is obtained ethyl rac-g-methy1-8-propyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetate. MS: 339 (M)+. which by saponification analogously to Example 1 is converted into the above acid which is used directly in the next step. rac-g-Methyl-8-Γ(RS)-1-methylpropyl]-6-(3-pyridyl)-6-triazolor4.3-a1pyrazine-3-acetic acid In analogous manner to that described in Example 1, by condensing 2-hydrazino-3-[(RS)-l-methylpropyl]-5-(335 - 41 -pyridyl)pyrazine with diethyl methylmalonate there is obtained ethyl rac-a-methyl-8-[(RS)-l-methylpropyl]-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate, MS: 353 (M) , which by saponification analogously to Example 1 is converted into the above acid which is used directly in the next step.

(IS,2R.3S)-3-Amino-l-cyclopropy1-4-pheny1-1,2-butanediol 9.96 ml (124.5 mmol) of bromocyclopropane in ether (100 ml) are added dropwise within 30 minutes under slight reflux to 3.03 g (124.5 mmol) of magnesium in absolute ether (10 ml) and the mixture is subsequently heated to reflux for 2 1/2 hours. Subsequently, 6.25 g (22.63 mmol) of tert.-butyl [IS,2R)-l-benzyl-2-cyano-2-hydroxyethyl]carbamate (EP-A 0.266.950) are added dropwise within 45 minutes under reflux and the mixture is heated at reflux for a further 2 1/2 hours. The mixture is then left to cool to 10°, 10% citric acid (100 ml) is added dropwise thereto and the mixture is extracted twice with 250 ml of ether each time. After usual working-up of the organic phase the crude product ΐε purified by flash chromatography on silica gel using a 9:1 mixture of toluene and ethyl acetate as the eluent. In this manner there are obtained 2.83 g (39%) of tert.-butyl [(1S,2R)-1-benzyl-2-(cyclopropylcarbonyl)-2-hydroxyethyl]carbamate, MS :246 (M-C3H9O) + . 2.83 g (8.77 mmol) of tert.-butyl [(IS,2R)-l-benzyl-230 -(cyclopropylcarbonyl)-2-hydroxyethyl]carbamate are dissolved in methylene chloride (130 ml), acetic acid (3 ml) is added thereto and the mixture is then treated portionwise at 0-10° with 332 mg (8.78 mmol) of sodium borohydride. The reaction solution is stirred at 5° for a further 2 hours and then partitioned between 2N sodium bicarbonate solution and methylene chloride. After the - 42 usual working-up of the organic phase the residue is crystallized from ether/hexane. whereby there are obtained 2.1 g (74%) of tert-butyl [(lS,2R,3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl]carbamate. melting point 83-85°. 2.0 g (6.23 mmol) of tert-butyl [ (IS.2R.3S)-1-(cyclohexyImethyl)-3-eyelopropyl-2.3-dihydroxypropyl]carbamate are dissolved in methanol (20 ml), 2N hydrochloric acid (20 ml) is added thereto and the solution is heated to 50° for 90 minutes.

The solution is neutralized by adding IN sodium hydroxide solution (40 ml) and concentrated to dryness under reduced pressure. The residue is partitioned between water and methylene chloride and the organic phase is worked-up as usual. There is thus obtained the desired (IS,2R.3S)-3-amino-l-cyclopropyl-4-phenyl-l.2-butanediol as a white, crystalline solid, yield 0.7 g (50.8%), MS: 150 (M-C4H8O)+.

(IR or S.2R or S)-1-f(IR.2S)-l-Amino-3-cyclohexyl-l-hydroxypropyl]-1.2-cyclohexanediol 1.28 g (5 mmol) of tert-butyl (IS)-(2-cyclohexyl-l-formylethyl)carbamate (EP-A 0.332.008) are dissolved in 25 ml of ether and there are added dropwise thereto at -78° 70 ml (7 molar eq.) of a 0.5 molar 1-lithium-l-cyclohexene solution (J.C.S. 1950. 2014) in ether.

Thereafter, the reaction solution is left to react at -78° for 1 1/2 hours and is subsequently heated to reflux for a further 48 hours. After the usual aqueous working-up the desired product is obtained as an epimer mixture which is separated into the individual components by chromatography on silica gel (eluent: 9:1 mixture of toluene and ethyl acetate). In this manner there obtained 270 mg (16%) of -43tert-butyl Γ(IS.2S)-2-(l-cyclohexen-l-yl)-l-cyclohexylmethyl)ethyl]carbamate as crystals and 800 mg (47%) of tert-butyl [(lS.2R)-2-(l-cyclohexen-l-yl)-l-(cyclohexylmethyl)ethyl]carbamate as an oil. R :0.4 and, F respectively. 0.35 (4:1 mixture of toluene and ethyl acetate ae the eluent). 260 mg of tert-butyl [(lS.2S)-2-(l-cyclohexen-l-yl)-l-(cyclohexylmethyl) ethylJcarbamate (or the epimeric tert-butyl [(IS.2R)-2-(1-cyclohexen-l-y1)-1-(cyclohexylmethyl ) ethyl ]carbamate) are dissolved in 2,2-dimethoxypropane (10 ml), 15 mg of p-toluenesulphonic acid mono15 hydrate are added thereto and the solution is stirred at room temperature for 3 hours. After the usual aqueous working-up the residue is chromatographed on silica gel (ethyl acetate/toluene; 9:1) and there are obtained 270 mg (39%) of tert-butyl (4S,5S)-5-(l-cyclohexen-l-yl)-420 -(eyeloheylmethy1)-2.2-dimethyl-3-oxazolidinecarboxylate, as an oil. Rp: 0.4 (9:1 mixture of ethyl acetate and toluene as the eluent). 340 mg (0.9 mmol) of tert-butyl (4S.5S)-5-(1-cyclohexen-l-y 1)-4- (eye loheylmethyl )-2. 2-d ime thy 1-3 -oxazo lid ine carboxylate in 36 ml of a 3:1 mixture of acetone and water are treated with 2.27 mmol of 4-methylmorpholine 4-oxide monohydrate and subsequently with 3.4 ml of osmium tetroxide solution (1 g of osmium tetroxide in 199 ml of 3Q t-butanol and 1 ml of t-butyl hydroperoxide. 70% in water) and the solution is stirred at room temperature for 4 hours. Subsequently, it is treated with 3.4 ml of 38% sodium bisulphite solution, concentrated under reduced pressure, extracted with ethyl acetate and there iB obtained after the usual workinq-up the desired product as a diastereomer mixture (9:1), which is separated by chromatoqraphy. Yield: 30 mq (8%) of the less polar epimer of tert-butyl (4S.5R)-4-(cyclohexylmethyl)-5-[(IS or R.2S - 44 or R)-l.2-dihydroxycyclohexyl]-2,2-dimethyl-3-oxazolidinecarboxylate as an oil. Rj.:0.3 (4:1 mixture of toluene and ethyl acetate as the eluent) and 330 mg (89%) of the more polar epimer tert-butyl (4S.5R)-4-(cyclohexylmethyl)-5-[(lR or S.2R or S)-1.2-dihydroxycyclohexyl]-2.2-dimethyl-3-oxazolidine carboxylate as a foam. RpiO.28 (4:1 mixture of toluene and ethyl acetate as the eluent). 310 mg (0.753 mmol) of tert-butyl (4S.5R)-4-(cyclohexylmethyl )-5- [ (IS or R.2S or R)-l.2-dihydroxycyclohexyl]-2.2-dimethyl-3-oxazolidinecarboxylate (or tert-butyl (4S.5R)-4-(cyclohexylmethyl)-5-[(IR or S.2R or S)15 -1.2-dihydroxycyclohexyl]-2.2-dimethy1-3-oxazolidinecarboxylate) are dissolved in 8 ml of methanol. 4 ml of 2N hydrochloric acid are added thereto and the mixture is stirred at room temperature for 22 hours. The reaction mixture is then evaporated under reduced pressure, toluene 2o is added thereto twice and evaporation under reduced pressure is carried out each time. In this manner there is obtained (IR or S.2R or S)-l-[(lR.2S)-l-amino-3-cyclohexyl-l-hydroxypropyl]-l.2-cyclohexanediol as an amorphous solid, Rp.:0.15 (65:10:1 mixture of methylene chloride. methanol and ammonia as the eluent).

Example A A sterile filtered, aqueous solution of (R or S)-N30 -[(IS.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl ]-8-propyl-a.6-bis(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide is mixed while warming with a sterile gelatine solution, which contains phenol as a preserving agent, under aseptic conditions so that 1.0 ml of solution has the following composition: - 45 (R or S)-N-[(IS,2R,3S)-1-(Cyclohexylmethyl)-3-cyclopropyl -2.3-dihydroxypropyl]-8-propy1-a,6-bis(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide 3.0 mg Gelatine 150.0 mg Phenol 4.7 mg Diet. Water ad 1.0 ml The mixture is filled into 1.0 ml vials under aseptic conditions .

Example B mg of (R or S)-N-[(lS,2R,3S)-l-(cyclohexylmethyl)-3-cyclopropyl-2,3-dihydroxypropyl]-8-propy1-a,6-bis(315 -pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide are dissolved in 1 ml of an aqueous solution with 20 mg of mannitol. The solution is filtered sterile and filled under aseptic conditions into a 2 ml ampoule, cooled to a low temperature and lyophilized. Prior to administration the lyophilizate is dissolved in 1 ml of distilled water or 1 ml of physiological saline. The solution is used intramuscularly or intravenously. This formulation can also be filled into double chamber injection ampoules.

Example C 500 mg of finely milled (R or S)-N-[(1S.2R.3S)-1-(cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-propyl-a.6-bis(3-pyridyl)-s-triazolo[4.3-a]pyraz ine30 -3-acetamide are suspended in a mixture of 3.5 ml of Myglyol 812 and 0.08 g of benzyl alcohol. This suspension is filled into a container having a dosage valve. 5.0 g of Freon 12 are filled under pressure into the container through the valve. The Freon is dissolved in the Myglyol-benzyl alcohol mixture by shaking. This spray container contains about 100 single doses which can be applied individually. - 46 Example D When the procedures described in Examples A-C are followed, corresponding galenical preparations can be manufactured from the following, likewise preferred, compounds: (R or S)-N-r(lS,2R.3S)-l-(Cyclohexylmethyl)-3-cyclopropyl-2.3-dihydroxypropyl]-8-isopropyl-α-(imidazol-4-ylmethyl)-6-(3-pyridyl)-s-triazolo[4.3-a]pyrazine-3-acetamide; (R or S)-N-[(lS.2R,3S)-l-(cyclohexylmethyl)-3-cyclohexyl-2,3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)-8-isobuty1-6-(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetate (R or S)-N-[(lS.2R.3S)-l-(cyclohexylmethyl)-2.3-di2o hydroxy-5-methylhexyl]-8-propyl-6-(3-pyridyl)-a-(3-pyridylmethyl)-s-triazolo[4.3-a]pyrazine-3-acetamide; (S or R)-N-[(1S.2R,3S)-1-(cyclohexylmethyl)-3-cyclopropy1-2.3-dihydroxypropyl]-8-[(RS)-1-methylpropyl]-a-(325 -pyridylmethyl)-6-(3-pyridyl)-s- triazolo[4,3-a]pyrazine-3-acetamide and N-[(1S,2R,3S)-1-(cyclohexylmethyl-3-cyclopropyl-2,3-dihydroxypropyl]-8-[(RS)-1-methylpropy1]-6-(3-pyridyl)-s30 -triazolof4,3-a]pyrazine-3-carboxamide.

Claims

Claims Amino acid derivatives of the general formula X NH \ wherein one of A and B signifies a nitrogen atom and the other signifies -CH- or both signify a nitrogen atom, one of X and Y signifies a nitrogen atom and the other signifies -CH- or both signify -CH-, R1 . . . . 2 . . . signifies phenyl, pyridyl or thienyl. R signifies 1. -16 and a therapeutically inert excipient. - 53 23. The use of an amino acid derivative according to any one of claims 1-16 in the control or prevention of i1lnesses. 5 24. The use of amino acid derivative according to any one of claims 1-16 in the control or prevention of high blood pressure and cardiac insufficiency. 25. The use of an amino acid derivative according to 10 any one of claims 1-16 for the manufacture of medicaments against high blood pressure and/or cardiac insufficiency. - 54 26. Amino acid derivatives according to one of claims 1-16, whenever prepared according to the process as claimed in claim 20 or by an obvious chemical equivalent thereof. - 55 27. The invention as hereinbefore described 28. A method of treating or preventing high blood pressure and/or cardiac insufficiency which comprises administering to a patient requiring such treatment an effective amount of an amino acid derivative according to

1 . . . . . 2 R signifies phenyl, pyridyl or thienyl. R 20 signifies alkyl or arylalkyl. R signifies hydrogen, alkyl, imidazol-2-ylmethyl. imidazol-4-ylmethyl, pyridylmethyl. pyrazol-3-ylmethyl, thien-2-ylmethyl. thiazol-4-ylmethyl. alkylthiomethyl, carbamoylmethyl, carbamoylethyl or benzyl and R signifies one of the 25 groups in which m signifies the number 2 or 3. - 51 18. Amino acid derivatives according to any one of claims 1-16 for use as therapeutically active substances 19. Amino acid derivatives according to any one of 5 claims 1-16 for use in the control or prevention of high blood pressure and cardiac insufficiency. 20. A process for the manufacture of a compound according to any one of claims 1-16. which process 1Q comprises a) reacting a compound of the general formula FL H,N‘ 2. . . . wherein R signifies alkyl or phenylalkyl, preferably 15 propyl, isopropyl, isobutyl. 1-methylpropyl or benzyl. 6. Compounds according to any one of claims 1-5,

2. Compounds according to claim 1, wherein A and B 5 each signify a nitrogen atom. 3. . . . 35 R signifies imidazol-4-ylmethyl or pyridyl-3-methyl, 3 . . . wherein R signifies hydrogen, imidazol-2-ylmethyl, imidazol-4-ylmethyl or pyridylmethyl. preferably 20 imidazol-4-ylmethyl or pyridyl-3-methyl. 7. Compounds according to any one of claims 1-6, 3. Compounds according to claim 1 or 2, wherein X signifies a nitrogen atom and Y signifies -CH-. 10 4. Compounds according to any one of claims 1-3, wherein R 1 signifies pyridyl, preferably 3-pyridyl. 5. Compounds according to any one of claims 1-4.

3 . . . alkyl or arylalkyl. R signifies hydrogen, alkyl, imidazol-2-ylmethyl, imidazol-4-ylmethyl, pyridylmethyl, pyrazol-3-ylmethyl, thien-2-ylmethyl, thiazol-4-ylmethyl. alkylthiomethyl, carbamoylmethyl, 4. 5 ... . . wherein R and R have the significance given in claim 1, with a compound of the general formula 12 3 wherein A. Β, X, Y, R . R and R have the significance given in claim 1. or an activated derivative thereof, and - 52 b) if desired, separating a mixture of diastereomeric racemates into the diastereomeric racemates or optically pure diastereomers, and/or 5 c) if desired, separating a mixture of diastereomers into the optically pure diastereomers, and/or d) if desired, converting a compound obtained into a pharmaceutically usable salt. 21. A medicament containing an amino acid derivative according to any one of claims 1-16 and a therapeutically inert excipient. 15 22. A medicament for the control or prevention of high blood pressure and cardiac insufficiency, containing an amino acid derivative according to any one of claims 4 . . . 5 . . . R signifies cyclohexylmethyl and R signifies - 49 group (a) in which m signifies the number 2 and R 6 signifies cycloalkyl. 11. (R or S)-N-[(IS,2R,3S)-1-(Cyclohexylmethy1)-35 -cyclopropyl-2,3-dihydroxypropyl]-8-propyl-a,6-bis(3-pyridyl)-s-triazolo[4,3-a]pyrazine-3-acetamide. 12. (R or S)-N-[(IS,2R,3S)-1-(Cyclohexylmethyl) -3-cyclopropyl-2.3-dihydroxypropylJ-8-isopropyl-a-(imidazol10 -4-ylmethy1)-6-(3-pyridy1)-s-triazolo[4.3-a]pyrazine-3-acetamide. 13. (R or S)-N-[(IS,2R,3S)-l-(Cyclohexylmethyl)-3-cyclohexy1-2,3-dihydroxypropyl]-a-(imidazol-4-ylmethyl)15 -8-isobutyl-6-(3-pyridyl)-s-triazolo[4.3-a]pyraz ine-3-acetate. 14. (R or S)-N-[(IS,2R.3S)-l-(Cyclohexylmethyl)-2,3-dihydroxy-5-methylhexyl]-8-propyl-6-(3-pyridyl)-a-(320 -pyridylmethyl)-s-triazolo[4,3-a]pyrazine-3-acetamide. 15. (S or R)-N-[(IS,2R,3S)-1-(Cyclohexylmethy1)-3-cyclopropyl-2,3-dihydroxypropyl]-8-[(RS)-1-methylpropyl]-a-(3-pyridylmethyl)-6-(3-pyridyl)-s-triazolo[4,3-a]25 pyrazine-3-acetamide. 16. N-[(1S.2R,3S)-1-(Cyclohexylmethyl-3-cyc1opropy1-2,3-dihydroxypropyl]-8-[(RS)-l-methylpropyl]-6-(3-pyridyl) -s-triazolo[4,3-a]pyrazine-3-carboxamide. 17. Compounds of the formulae IV V and III' 10 wherein B signifies an amino protecting group. R 4 signifies cyclohexylmethyl. benzyl or isobutyl. R 6 signifies cycloalkyl, alkyl, alkenyl or arylalkyl. n signifies the number 3 or 4. one of A' and B' signifies a nitrogen atom and the other signifies -CH- or 15 both signify a nitrogen atom and one of X and Y signifies a nitrogen atom and the other signifies -CH- or both signify -CH-, with the proviso that X signifies -CH- when A' and B' each signify a nitrogen atom,, 4 . . . wherein R signifies cyclohexylmethyl. 25 8. Compounds according to any one of claims 1-7. 5 . . . wherein R signifies group (a). 9. Compounds according to claim 8, wherein m 6 . . signifies the number 2 and R signifies cycloalkyl. 10. Compounds according to any one of claims 1-9, wherein A. B and X each signify a nitrogen atom. Y . . 1 . . . 2 signifies -CH-, R signifies 3-pyndyl, R signifies propyl, isopropyl, isobutyl. 1-methylpropyl or benzyl,

4 . . . carbamoylethyl or benzyl. R signifies cyclohexyl5 . . . methyl, benzyl or isobutyl and R signifies one of the groups OH I —(CH) m -—R 6 (a) .6 (b) and in which R signifies cycloalkyl, alkyl, alkenyl or arylalkyl, m signifies the number 2 or 3 and n signi fies the number 3 or 4, in the form of optically pure diastereomers, mixtures of diastereomers, diastereomeric racemates or mixtures of - 48 diastereomeric racemates as well as pharmaceutically usable salts of these compounds.

5. Any one of claims 1-16.