CA1088520A

CA1088520A - Process for the manufacture of dipeptide derivatives

Info

Publication number: CA1088520A
Application number: CA274,078A
Authority: CA
Inventors: Eberhard Schwertner; Leopold A.N. Flohe; Siegfried Herrling
Original assignee: Gruenenthal GmbH
Current assignee: Gruenenthal GmbH
Priority date: 1976-04-09
Filing date: 1977-03-16
Publication date: 1980-10-28
Also published as: DK148902B; IE44485L; DK148902C; ATA113977A; FR2347338A1; GB1564078A; FR2347338B1; PT66283A; JPS52125166A; YU85977A; AU2322677A; SE427835B; DE2615455C2; DK157077A; BE853444A; JPS6110479B2; DE2615455A1; PT66283B; ES457563A1; AT352921B

Abstract

ABSTRACT OF THE DISCLOSURE
Process for the manufacture of dipeptide derivatives derived from histidyl-proline of the general formula

Description

i520 The present invention relates to a process for the manufacture of dipeptide derivatives, which are derived from histidyl-proline, one or both of the amino acids contained therein being optically active or racemic, but preferably having the L-configuration. More precisely the invention relates to the manufacture of compounds of formula (I) ~ ~ R

\ ~ J - NN G~ - C0 - ~ C0 - N \

and salts of these compounds with pharmaceuticaIly acceptable acids.
In formula (I) the radicals Rl and R2 are the same or different, -and each represent an alkyl or a cycloalkyl radical containing up to six carbon atoms or a benzyl group or represent - together with the nitrogen atom to which these radicals are attached - a five to seven membered hetero~
cyclic ring, R2 also may be a hydrogen atom. R3 and R4 are the same or different and each represent hydrogen or an alkyl radical containing from one to three carbon atoms. R3 and R4 together also can represent an addition-al bond between the carbon atoms to which these radicals are attached. R5 represents a hydrogen atom or an alkyl radical containing from one to three carbon atoms. Z represents a divalent structure which completes the ring to give a five- or six-membered ring, said divalent structure being selected from the structures:

pH
- NH -, - N = ~ -, - NH - C0 -, ; 20 lR6 16 - C - S -, and - f o . .
_ 1 - ~

wherein R6 and R7 are the same or different and each represent hydrogen or an alkyl radical containing from one to three carbon atoms.
The dipeptide derivatives of formula (I) are acyl derivative~ of histidyl_proline amides which may be derived from a carboxylic acid of formula (II):

~' " / S

¦ R4 ¦ / 3 \ N / b OOH (II) H

Preferred acids of formula (II) for use in preparing the dipeptides of the present invention are orotic acid, imidazolidine-(2)-one-(4)-carboxylic acid and thiomorpholine-(5)-one-(3)-carboxylic acid. Other suitable acids of formula (II) are for instance, morpholine-(5)-one-(3)-carboxylic acid, (4)-carboxy-imidazole-(2)-one, thiomorpholine-(6)-methyl-(5)-one-(3)-carboxylic acid, 5-methyl-, 5-ethyl- and 5-propyl-orotic acid, and thio rpholine-(5)-one-(2,2)-dimethyl-(3)-carboxylic acid.
Where R3 and R4 do not represent a second bond between the carbon -atoms to which said members are connected and/or in the case that R6 and R7 are different, the acyl groups derived from the acid of formula (II) can be present in the compound of formula (I) in racemic or optically active fonm, and are preferably in the L_configuration.
If R2 represents a hydrogen atom, Rl preferably is a straight chain alkyl radical containing up to six carbon atoms, especially a radical contain-ing one to four carbon atoms.
Where Rl and R2, together with the nitrogen atom to which these radicals are attached, represent a heterocyclic radical, this group may be the pyrrolidino-, the piperidino- or the hexamethylenimino-group or the 1(~5;~0 residue of a five to seven membered heterocyclic ring containing at least one further hetero atom, such as the thiazolidino-, morpholino- or thiomorpholino-eroup .
Due to the basicity of the histidyl radical the compounds of fonmula (I) can form salts with acids. A further object of the present invention accordingly is the preparation of salts of the compounds of formula (I) to provide pharmaceutically acceptable salts of inoreanic or organic acids, such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, propionic acid, benzoic acid, salicylic acid, phenyl acetic --~
acid and benzenesulfonic acid.
Surprisingly the compounds of formula (I) (and their salts) possess biological properties, which with respect to their effectiveness are nearly the same as those of pyroglutamyl-histidyl-proline amide, which compound normally is designated as "tyrotropine releasing hormone" or nTRHn. The effects of the new compounds, however, last considerably longer than those of the known product. Of special value in therapy is that the relation of the central nervous system stimulating effects to the endocronologic effects is shifted for the new compounds (if compared with those effects of TRH) favorably to the pharmacologically valuable properties.
The compounds of formula (I) may be administered orally or parenter-ally and act quickly For instance on parenteral administration the effects are observed after 10 minutes.
The most impressive effects in pharmacological tests indicate a central nervous system stimulating action for the new products. On administer-ing equal doses of TRH and one of the new products, respectively, to test animals the new compound has a central nervous system stimulating action which is several times longer than TRH.
The toxicity of the compound of formula (I) is very low. Due to these valuable properties the new compounds can be used as therapeutics, for lO~S~O

instance as psychostimulating agents or anti-depressive agents. The compounds are of therapeutic value in animals and humans.
Suitable pharmaceutical preparations containing the compounds of formula (I) or their salts are tablets for oral use, dragees, granules, capsules, drops, syrups, sprays for intranasal application or administration via bronchial sprays, and for parenteral application, sterile a~ueous solutions.
These pharmaceutical preparations are prepared as is known in the prior art with inert carriers, such as is known for other anti-depressants and CNS-stimulants used in human and warm-blooded animal therapy.
The therapeutically effective dosage of the new compounds depends on the severity of the depression to be treated and also on the route of a~min-istration. Preferably the compounds of the invention are used parenterally in a dosage of 0.005 to 0.5 mg/kg and orally in a dosage of 0.05 to 5 mg/kg. When the therapy does not call for such dosages as stated, the dosage _ay be in-creased or decreased as recommended by the circumstances.
The compounds of formula (I) are prepared by reacting a histidyl-proline amide (having the desired optical configuration) of formula (III), IN

H N - C - C0 - ~ C0 - ~ (III), wherein Rl and R2 have the same meaning as above with an acid of formula (II) in the presence of an agent, which is able to split off water, especially in presence of a carbodiimide, preferably dicyclohexyl carbodiim;de, or with a - functional derivative of an acid of formNla (II), as for instance an acid lO~iS~O

halide, anhydride, mlxed anhydride, azide or an acti~ated ester thereof.
Instead of the acid of formula (II) or a functional derivative thereof, also a compound of formula (IIa) , - _ / R5 I ¦ \ R

/ 3 (IIa), \ / ~COOH

Y

wherein R3, R4, R5 and Z have the same meaning as above and Y represents a group cleavable by hydrogenolysis, preferably a carbobenzoxy group or a substituted carbobenzoxy group, or a functional derivative of the acid of formula (IIa), as for instance an acid halide, anhydride, mixed anhydride, azide or an activated ester, may be used.
During the reaction of the histidyl-proline amide of formula (III) with the acid of fonmula (II) or (IIa) or a derivative thereof, the 1-(3)-position of the ~midazole group of the histidyl residue may be protected against acylation.- Suitable protective groups are known from peptide synthesis to those skilled in the art. Such groups are for instance the carbobenzoxy group, substituted carbobenzoxy groups, the trityl, o-nitrophenoxy acetyl or the tert.-butyloxycarbonyl group and other groups known E~ se, which after the reaction is completed can be split off by hydrolysis or hydrogenolysis.
Instead of the histidyl-proline amide of formula (III) with either a free or protected imidazole group, a derivative thereof, obtained by reacting it in a manner known per se with a silylating agent, derived from a triaIkyl-silanol or a dialkylsilanediol (each alkyl radical thereof containing from one to three carbon atoms) as for instance hexamethyldisilazene, trimethylchloro-silane, trimethylsilylacetamide or dimethyldichlorosilane and the known ., _ 5 _ S'~
equivalents thereof, may be used in the process of the present invention.After the acylation reaction (which in this case has to be perfor~ed in absence of a proton active solvent) is finished, the silyl groups can easily be split off by hydrolysis or alcoholysis.
In preparing the compounds of formula (I) it is possible also to react a compound of fonmula (IV):

, ` / R5 I ¦ \ R

l\ 1 ~ 3 ~ \ N / ~ NH - CH - COOH (IV), wherein R3, R4, R5 and Z have the same meaning as above and X represents a hydrogen atom or a group of type Y as defined before, or a derivative of the compound of formula (IV) in which the 1-(3)-position of the imidazole group is protected reversibly as described above, in the presence of an agent which is able to split off water, especially in presence of a carbodiimide, preferably dicyclohexyl carbodiimide or with a functional derivative of a compound of formula (IV) as for instance an acid halide, anhydride, mixed anhydride or an activated ester with a compound of formula (V), ~ ON / (V), `

wherein R1 and R2 have the same meaning as above and thereafter splitting off any protecting groups; if present.
Furthermore compounds of formula (I) can be prepared by reacting a compound of formula (VI) iO~i5;~0 - _ ~ R5 ~ R3 ~NH (VI), O \ N CO - NH - CH - CO - N ~ O - W

wherein R3, R4, R5, ~ and Z have the same meaning as above and W repreQent~ a hydroxy, acyloxy, p-nitrophenoxy, tri- or pentachlorophenoxy-, pentafluoro-phenoxy, pyridyloxy, phenylmercapto, p-nitrophenylmercapto or cyanomethyloxy group or the residue of N-hydroxysuccinimide, or a derivative of the compound of formula (VI) wherein the 1-(3)_position of the imidazole group is protected reversibly in the manner described hereinabove, with an ~mine of formula (VII), Rl -HN~/ (VII) wherein Rl and R2 have the same meaning as above and splitting off any pro-tecting groups, if present.
Compounds of fonmula (I), (one or both of the amino acid groups contained therein being optically active or racemic but preferably having the ;~
L,configuration) derived from orotic acid, wherein Rl and R2 have the same meaning as above, provided that neither of these radicals may be a benzyl :~ group in this instance, are preferably manufactured by reacting the compound of formula (III) having the desired optical configuration with an acid of the formNla:

~o~
IN N OCH (VIII) lO~S;~O
wherein Hal represents a chlorine or a bromine atom in the presence of an agent able to split off water, especially in the presence of a carbodiimide, preferably dicyclohexylcarbodiimide or with a functional derivative of such an acid of formula (VIII), as for instance an acid halide, anhydride, mixed anhydride, azide or an activated ester thereof, and thereafter dehalogenating the intermediate by hydrogenolysis.
During the reaction of the compound of formula (III) with the acid of formula (VIII) or the derivative thereof, the 1-(3)-position of the imida-zol group of the histidyl residue may be protected against acylation. Suit-able protective groups are those mentioned already hereinabove. In this lastdescribed method, it is especially useful to employ such protective groups as can be split off by hydrogenolysis (as for instance the carbobenzoxy group, substituted carbobenzoxy group or the o-nitrophenoxyacetyl group). In this case the removal of the protective group from the intermediate occurs coin-cidently with the hydrogenolysis of the halogen atom. Naturally, it is also possible, however, to protect the imidazole group with such groups, which can be split off by hydrolysis (as for instance trityl or tert. butyloxycarbonyl groups and others) and to remove such protective groups from the intermediate product or from the product obtained by hydrogenolysis of the halogen atom from the intermediate.
The hydrogenolysis of the halogen atom is preferably carried out by means of catalytically activated hydrogen. Preferably a noble metal hydrogena-tion catalyst, as for instance palladium or platinum on charcoal, on barium sulfate, on alumina, on calcium or barium carbonate and other noble metal catalysts known E~ se, are used inthehydrogenolysis, which can be perfonmed under nonmal or increased pressure , preferably at room temperature. Solvents like water or mixtures of water with lower alcohols (methanol, ethanol) or with tetrahydrofuran and dioxane are preferably used in the hydrogenolysis step. It is, however, also possible to use glacial acetic acid for example.

lO~S~O
The hydrogen halide formed during the hydrogenolysis is preferably bound as soon as it is formed. To that end the hydrogenolysis is preferably performed in the presence of an agent which is able to bind hydrogen halides.
If the abovementioned preferred or other non-acidic solvents are used, suit-able hydrogen halide binding agents are for instance magnesium oxide, barium oxide, aIkali hydroxides, ammonia or ammonium hydroxide, triethyl~mine or salts of such bases with acids which are very much weaker than the hydrogen halide being formed, as for instance aIkali carbonates or acetates. Suitable media for the performance of the hydrogenolysis step also include for instance, solutions of aIkali metal, aIkaline earth metal, ammonium or amine acetates in acetic acid.
Mixed anhydrides of the acids of formulae (II), (IIa), (n) and (VIII) are preferably obtained from trimethylacetic acid or from noesters of carbonic acid especially those in which the carbonic acid is esterified with aliphatic alcohols containing from one to four carbon atoms. Suitable activated esters of such acids are those with p-nitrophenol, tri- or penta-chlorophenol, pentafluorophenyl, N-hydroxysuccinimide, 2- or 4-~ydroxypyridine, thiophenol, p-nitrothiophenol, hydroxyacetonitrile, l-hydroxybenzotriazole and other h~vdroxy- or mercapto compounds conventionally used in peptide chemistry to prepare activated esters from acids.
The compounds of formula (I) and their salts are relatively stable products. They can therefore be purified for instance, by dissolving and reprecipitation, by recrystallization~ and also by column chr~matography or counter-current distribution.
The following non-limiting examples further illustrate the invention.
All temperature references are uncorrected.
E~llMPI~: 1 a) ~ solution of 12.7 g of methylamine in 350 ml of absolute tetrahydro-; furan is treated, while stirring, at o& with 71 g of the N-hydroxysuccinLmide l(U~S~O

ester of benzyloxycarbonyl-L-proline.
The mixture is stirred for 15 minutes at o& and thereafter for two hours at room temperature. After distilling off the sol~ent in ~ac~um the residue is dissolved in ethyl acetate, which solution is washed with a 5%
aqueous solution of potassium hydrogen sulfate, a saturated aqueous solution of sodium hydrogen carbonate and finally with water. The solution is dried with anhydrous sodium sulfate and evaporated. Thus 46 g (85% of the theoret-ical yield) of benzyloxycarbonyl-L_proline-N-methylamide are obtained in the form of a colorless, viscous oil which crystallizes on storage at 3 - 5 C, but melts at room temperature.
b) 102.3 g of benzyloxycarbonyl-L_proline-methylamide dissolved in methanol are treated in the presence of freshly prepared palladium black and 22.3 ml of glacial acetic acid with hydrogen. The catalyst is filtered off and the solution is mixed with 100 ml of 4 N hydrochloric acid, then e~aporated in vacuum, mixed with absolute ethanol and again evaporated. The crystalline residue is recrystallized from methanol/ether (3:10). The product is dried in vacuum over phosphorus pentoxide. Thus 49.7 g (77% of the theoretical yield) of L_proline-methylamide hydrochloride melting at 165 C are obtained. [~]D =
_ 55.3 (c = l; methanol)-c) To a suspension of 60.8 g of benzyloxycarbonyl-L_histidinhydrazide -in 400 ml of dimethylformamide which is chilled to - lS to - 20& are added 228 ml of a 4.38 molar solution of hydrogen chloride in absolute tetrahydrofuran.
- While stirring, 24 ml of tert.butyl nitrite are added in such manner than the temperature remains below -15 & . Thereafter the mixture is stirred for 30 minutes at - 15 & , chilled to - 45 & and then treated dropwise with 139 ml of triethylamine at a temperature below - 30 C. 32.9 g of L_proline-methyl~mide ; hydrochloride, 27.8 ml of triethyl~ine and, 15 minutes later, 22 ml of N-methylmorpholine are added. The reaction mixture is stirred for 24 hours, during which time it is allowed to wanm to room temperature. The precipitate _ 10 --~(t~ ~ S ~ O

fonmed is separated and the filtrate is evaporated under reduced pressure.
The residue is dissolved in 300 ml of water containing a small amount of hydrochloric acid. On bringing the pH value to 9 by adding a concentrated aqueous solution of ammonia, an oil separates which is isolated by decanting the aqueous layer and dissolved in tetrahydrofuran. This solution is diluted with the same volume of ethyl acetate and then extracted several times with water. The organic layer, after drying over sodium/sulfate is evaporated under reduced pressure. After drying the residue over phosphorus pentoxide in vacuum benzyloxycarbonyl-L histidyl-L_proline-methylA~ide is obtained in form of a solid foam. Yield: 46.5 g - 58% of the theoretical. []D = ~40 3 (c = l; methanol).
d) 30 g of benzyloxycarbonyl-L histidyl-L proline-methylamide are dissolved in 100 ml of glacial acetic acid and treated with 100 ml of a 40%
solution of hydrogen bromide in glacial acetic acid. After stirring for one hour at room temperature, 500 - 600 ml of dry ether are added, the precipitate formed is separated, washed with dry ether and dried in vacuum over phosphorus pentoxide and potassium hydroxide. The hydrobromide of L,histidyl-L-proline-methylamide thus obtained, 12.8 g of thiomorpholine 4 -(D,L)-methyl-5-on-3-(L)-carboxylic acid and 10.5 g ofl-hydroxybenzotriazole are dissolved in 150 ml of dimethylformamide, chilled to -5 to 0 and treated with the amount of tri-ethylamine being equivalent to the amount of hydrogen bromide present in the mixture. Finally 15 g of N,N1-dicyclohexyl-carbodi;m;de dissolved in a few ml of dimethylformamide are added. After stirring for 10 minutes in the ice bath the mixture is stirred for 12 hours, during which time it is allowed to reach room temperature. The precipitate formed is separated, the filtrate is evapo-rated under reduced pressure and the residue thus obtained is dissolved in 150 ml of water and stored at 3C. After filtration the filtrate is mixed with an equal volume of methanol and treated with a cationic e~changer in free acidic ; state as, for instance, the product known under the trade name "Dowex 50 W~ 4n 10~5~
The cationic exchanger carrying the product is separated by filtration, wa~hed with methanol and water and then it is slurried in methanol/water (1:1) and treated, while stirring, with ammonia until the pH of the mixture is 9.5.
The exchanger resin is separated and the filtrate is evaporated under reduced pressure. The residue is recrystallized twice from a small volume of water and then dried over phosphorus pentoxide. Thus 9.4 g of 5-Oxo-6-(D,L)-methyl-thiomorpholine-3-(L)-carbonyl-L-histidyl-L,proline-N-methylamide melting at 138 - 139 & are obtained. [a]D = - 48.0 (c = l; methanol).

The procedure is the same as in example ld, there are used however 11.4 g of orotic acid (anhydrous) instead of the thiomorpholine-6-(D,L)-methyl-5-on-3(L)-carboxylic acid. The residue remaining after evaporating the eluate of the cationic exchanger is recrystallized twice from ethanol/
ether (4:1) and once from ethanol. The product is dissolved in water and lyophylized. After drying over phosphorus pentoxide 5.4 g of orotyl-L-histidyl-L proline-N-methylamide are obtained. The melting point of the product is not characterizing. [a]D = -46.6 (c = l; methanol).
The combined mother liquors are evaporated and the residue thus obtained is recrystall;zed several times from isopropanol. After drying of the product in vacuum, a second batch of 3.6 g of the desired compound is obtained.

The procedure is the same as in example ld, there are used however 35 g benzyloxycarbonyl-L,histidyl-L,proline-cyclohexylamide instead of the benzyloxycarbonyl-L,histidyl-L,proline-methylamide and 11.4 g of orotic acid (as in example 2). The eluate of the cationic exchanger is evaporated and the residue is further purified by column chromatography on silicagel (particle size 0.063 - 0.200 mm), using ethanol~water (5:1) for elution. On evaporation of the eluate, ~.6 g of orotyl-L_histidyl-L_prolin-cyclohexylamide are obtained.

_ 12 --S~

[]24= _54 3 (c = 0.3; methanol).

a) Using the procedure described in example la, 20 ml of n-butylamine are reacted with 69.2 g of the N-hydroxy-succinimide ester of benzyloxycarbon-yl-L-proline. The desired product is recrystallized from ethylacetate/ligroin (1:1). After drying in vacuum 49.8 g (82 % of the theoretic yield) of benzyloxycarbonyl_L,proline_(n_butyl)_amide melting at 84-85 & are obtained.
[~]D5= -48.9 (c = 1; methanol).
b) 60.8 g benzyloxycarbonyl-L,proline-(n-butyl)-amide are hydrogenated in presence of palladium black and 11.6 ml of glacial acetic acid as described in example lb. Thereafter 50 ml of 4 N hydrochloric acid are added, the mix-ture is evaporated and the residue dissolved in ethanol. The oil remaining after distilling off the ethanol is crude L,proline-(n-butyl)-amide-hydro-chloride, which without further purification is used in the next step.
c) The product obtained in example 4b is used in the procedure of example lc instead of the L_proline-methylamide-hydrochloride. The residue obtained on evaporating the reaction mixture in vacuum is treated with water, then with ammonia (until pH 9.5 is reached). This solution is extracted several times with ethyl acetate. The combined extracts are washed consecu-tively with water, 10~ aqueous sodium carbonate solution and water. Theorganic layer is dried over sodium sulfate and evaporated. After drying the residue in vacuum 53 g (60% of the theoretical yield) of benzyloxycarbonyl-L, histidyl-L,proline-(n-butyl)-amide are obtained in form of a porous mass.
[~]D = ~ 47.6 (c = 1; methanol).
d) The procedure is as described in example 3, there are used however 33.1 g of benzyloxycarbonyl-I-histidyl-L,proline-n-butylamide and 11.4 g of orotic acid, the elution from the column of silicagel being made with methanol in this instance. ~hus 10.8 g (33.4 ~ of the theoretical yield) of orotyl-L, histidyl-I-proline-N-(n-butyl)-amide are obtained. []D = ~ 55.0 (c = O.S;

_ 13 -SZO
methanol).
E~IE _ The procedure is the same as in example ld, there are used, however, 35.2 g benzyloxycarbonyl-L,histidyl-L,proline-(n-hexyl)_amide and 11.4 g orotic acid. The residue obtained on distilling off the dimethylfonmamide is dis-solved in methanol/water tl:l) and treated (as described) with a cationic exchanger resin. The eluate of the exchanger resin is evaporated. The resi-due is dissolved by adding 50 ml of water and 4 N hydrochloric acid until pH 3 is reached. A small amount of impurities is filtered off, the filtrate evaporated in vacuum and the residue recrystallized twice from n-butanol, saturated with water. The substance thus obtained is dissolved in water, which solution is extracted several times with n-butanol. The combined ex-tracts are evaporated in vacuum. Thus 7.9 g (21% of the theoretical yield) of orotyl-I-histidyl-L-proline-(n-hexyl) amide-hydrochloride melting at 180-185 C
are obtained. ~a]D = -57.8 (c = 1; methanol).
The combined mother liquors are evaporated and the residue is sub-jected to counter-current distribution in the system n-butanol/water. Thus further 5.7 g (15% of the theoretical yield) of the desired product are obtained.
0 EXAMPL~ 6 a) 24.9 g of benzyloxycarbonyl-I-proline are dissolved in 150 ml of absolute tetrahydrofuran and then 13.9 ml of triethylamine are added while stirring. After chil~;ng to - 15C, a solution of isobutyl-chlorocarbonate in 50 ml of absolute tetrahydrofuran and, after 5 minutes, a solution of 10.1 ml of piperidine in 50 ml of absolute tetrahydrofuran are added dropwise at this temperature. The mixture is stirred for two hours longer, during which time it is allowed to reach room temperature, and then evaporated in vacuum.
The residue is treated with ethyl acetate, and this solution is consecutively extracted with water, 5% aqueous potassium hydrogensulfate solution, saturated - 14 _ S;~O
aqueous sodium carbonate solution and water. After drying the solution over sodium sulfate, the ethyl acetate is distilled off and the residue is tri-turated with ether and then recrystallized from ethylacetate/ligroin (2:3).
Thus 21.2 g (67g of the theoretical yield) of benzyl oxycarbonyl-L,proline-piperidide are obtained. Melting point 92 & . [a]23 = -21.9 (c = l; methanol).
b) 63.2 g of benzyloxycarbonyl-L_proline-piperidide are treated with hydrogen in presence of palladium black and 11.6 ml of glacial acetic acid as described in example lb. After the addition of 50 ml of 4 N hydrochloric acid the mixture is evaporated and the residue is dissolved in ethanol. The oil remaining after distil~ing off the ethanol is crude L-proline-piperidide-hydrochloride, which without further purification is used in the next step.
c) The product obtained in example 6b is used in the procedure described in example lc instead of the L,proline-methylamide-hydrochloride. The residue obtained on evaporating the filtered reaction mixture in vacuum is purified as described in example 4c. The oily residue obtained after distilling off the ethyl acetate is dissolved in a small amount of methanol and reprecipitated by addition of ether. The solvents are decanted and the product is dried in vacuum, whereby 46.5 g (51% of the theoretical yield) of benzyloxycarbonyl-L-histidyl-L-proline-piperidide are obtained in the fonm of a porous mass.
0 [a]D = ~ 51.3 (c = 1; methanol).
d) The procedure is as described in example 3, there are used however 33.6 g of benzyloxycarbonyl-L,histidyl-2-proline-piperidide and 11.4 g of orotic acid, the elution from the column of silica gel being made with ethanol in this instance. Thus 10.9 g (32% of the theoretical yield) of orotyl-I-histidyl-l_proline-piperidide are obtained. ~a]D = -62.5 (c = 0.5; methanol).
EXAMP~E 7 a) The procedure is the same as in example 6a. However 11.2 ml of benzyl amine are used instead of the piperidine. The produce is purified by recrys-tallization from ethyl acetate/ligroin (1:1). After drying in vacuum, 24.3 g _ 15 --lO~blS20 (72~ of the theoretical yield) of benzyloxycarbonyl-L_proline-benzyla~ide are obtained. Melting point: 93 - 94 C. [a]D3 = - 43.5 (c = l; methanol).
b) 67.7 g of benzyloxycarbonyl-L,proline-benzylamide are dissol~ed in 300 ml of glacial acetic acid and treated with 240 ml of a 40% solution of hydrogen bromide in glacial acetic acid After stirring for 90 minutes at room temperature, the mixture is evaporated in vacuum. The residue is dissol-ved in a small amount of methanol and reprecipitated by adding of ether. The solvents are decanted, and the precipitate is triturated with ether and fin-ally dried in vacuum. The crude-L,proline-benzylamide-hydrobromide thus 0 obtained is used in the next step.
c) The crude product obtained in example 7b is used in the procedure described in example 4c. Thus 80.7 g (85% of the theoretical yield) of benzyloxycarbonyl-L,histidyl-L,proline benzylamide are obtained in the form of a porous mass. [a]D = - 39.1 (c = 1; methanol).
d) The procedure is as described in example 4d, there are used, however, 35.6 g of benzyloxycarbonyl-I,histidyl-I-proline-benzylamide and Il.4 g of orotic acid. Orotyl-l,histidyl-L,proline-N-benzylamide is obtained in a yield of 11.7 g (=33.3% of the theoretical yield. [a]D = - 50.~ (c = 1; methanol).
Following the procedures described above, especially those explained in the examples, the following compounds of formula (I) can also be prepared, for example. (In cases where no particulars of the configuration are given, any of the acid components of the compounds of formula (I), i.e. the proline, the histidine and the acid of formula (II), can be present in the racemic state, in the L, or in the D-configuration. As stated already above, the L_ configuration is preferred, however, for said components):
Orotyl-I-histidyl-L,proline-morpholide L,2-Oxo-imidazolidine-4-carbonyl-l-histidyl-L_proline-N-methylamide 5-iso-propylorotyl-histidyl-proline-N-ethylamide

2-Oxo-5,5-dimethyl-imidazolidine 1-carbonyl-histidyl-proline-N-methylamide.

S;~O

2-Oxo-4,5-dimethyl-imidazolidine 1-carbonyl-histidyl-proline-N-methyla ide.
2-Oxo-5-ethyl-imidazolidine-4-carbonyl-histidyl-proline-N-ethylamide 2-Oxo-5-methyl_5-ethyl-imidazolidine 1-carbonyl-histidyl-proline-N-isopropyl-amide.
5-Oxo-2,2,6-trimethyl-thiomorpholine-3-carbonyl-histidyl-proline-N-methylamide.
5-Oxo-2,3,6-trimethyl-thiomorpholine_3_carbonyl-histidyl-proline-pyrrolidide 5-Oxo-6,6-dimethyl-thiomorpholine-3-carbonyl-histidyl-proline-N_methylamide 5-Oxo-morpholine-3-carbonyl-histidyl-proline-N-benzylamide 5-Oxo-6-methyl-morpholine-3-carbonyl-histidyl-proline-N-methylamide 5-Oxo-2,6-dimethyl-morpholine-3-carbonyl-histidyl-proline-N-methylamide 5-Oxo-6-(DL)-methyl-thiomorpholine-3(L)-carbonyl-L,histidyl-L_proline-N-(n-hexyl)-amide. -S-Oxo-thiomorpholine-3-carbonyl-histidyl-proline-N-methylamide 5-Oxo-thiomorpholine-3-carbonyl-histidyl-proline-N-benzylamide 5-Oxo-thiomorpholine-3-carbonyl-histidyl-L-proline-morpholide.

;

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of the dipeptide derivatives of formula (I):

(I) wherein R1 and R2 have the same or a different meaning and each represents an alkyl or cycloalkyl radical containing up to six carbon atoms or a benzyl group or both, together with the nitrogen atom to which these radicals are attached, represent a five to seven membered heterocyclic ring, or wherein R2 represents a hydrogen atom, R3 and R4 have the same or a different meaning and each represent hydrogen or an alkyl radical containing from one to three carbon atoms or together represent an additional bond between the carbon atoms to which they are attached, R5 represents a hydrogen atom or an alkyl radical containing from one to three carbon atoms, and wherein Z represents a divalent group, being one of the structures:

- NH -, , - NH - CO - or , wherein R6 and R7 have the same or a different meaning and each represent hydrogen or an alkyl radical containing from 1 to 3 carbon atoms and salts of the compounds of formula (I) with pharmaceutically acceptable acids, by reacting:

a) a carboxylic acid of the formulae (II) or (IIa) wherein R3, R4, R5 and Z have the same meaning as above and Y represents a group cleavable by hydrogenolysis, in the presence of an agent, which is able to split off water or a functional derivative of an acid of formula (II) or (IIa), respectively, with a compound of formula (III), (III) wherein R1 and R2 have the same meaning as above and in which the 1-(3)-position of the imidazole group of the histidyl residue may be protected against acylation, or a derivative thereof obtained by reacting the compound of formula (III) in a manner known per se with a silylating agent derived from a trialkylsilanol or a dialkylsilanediol (each alkyl radical of said silylating agents containing from one to three carbon atoms) and splitting off in a manner known per se the group Y, the protecting group from the imidazole group contained in the histidyl residue and the silyl groups, if present; or b) a compound of the formula, (IV) wherein R3, R4, R5 and Z have the same meaning as above and X represents a hydrogen atom or a group Y as defined before, or a derivative of the compound of formula (IV) in which the 1-(3)-position of the imidazole group is pro-tected reversibly (as described previously) in presence of an agent which is able to split off water, or a functional derivative of a compound of formula (IV) with a compound of formula (V) (V) wherein R1 and R2 have the same meaning as above and splitting off any pro-tecting groups, if present, or c) a compound of formula (VI) (VI) wherein R3, R4, R5, X and Z have the same meaning as above and W represents a hydroxy, acyloxy, p-nitrophenoxy, tri- or pentachlorophenoxy-, pentafluoro-phenoxy, pyridyloxy, phenylmercapto, p-nitrophenylmercapto or cyanomethyloxy group or the residue of N-hydroxysuccinimide, or a derivative of the compound of formula (VI) in which the 1-(3)-position of the imidazole group is protected reversibly as described previously, with an amine of formula (VII), (VII) wherein R1 and R2 have the same meaning as above and splitting off any pro-tecting groups, if present; or d) a compound of formula (III), wherein R1 and R2 have the same meaning as above, provided that neither of these radicals may be a benzyl group in this instance, and in which the 1-(3)-position of the imidazole group may be protected against acylation preferably by a group cleavable by hydrogenolysis, with an acid of the formula:

(VIII) wherein Hal represents a chlorine or a bromine atom in the presence of an agent capable of splitting off water or with a functional derivative of such an acid of formula (VIII), and thereafter dehalogenating the intermediate by hydrogenolysis and effecting removal of the protecting group, if present to give such compounds of formula (I) in which R3 and R4 form an additional bond between the carbon atoms to which they are attached, R5 is hydrogen and Z
represents -N=C(OH)- or -NH-CO-, respectively.

2. Dipeptide derivatives of the formula, (I) in which R1 and R2 are the same or different and each represent an alkyl or cycloalkyl radical containing up to six carbon atoms or a benzyl group or both, together with the nitrogen atom to which they are attached, represent a five to seven membered heterocyclic ring, or in which R2 represents a hydrogen atom, R3 and R4 are the same or different and each represent hydrogen or an alkyl radical containing from one to three carbon atoms, or where R3 and R4 together can also represent an additional bond between the carbon atom to which these radicals are attached, R5 represents a hydrogen atom or an alkyl radical containing from one to three carbon atoms, and Z represents a divalent structure which completes the ring to give a five- or six-membered ring, said divalent structure being selected from the structures, , , , and , wherein R6 and R7 are the same or different and each represent hydrogen or an alkyl radical containing from one to three carbon atoms, and pharmaceutically acceptable acid salts thereof, whenever prepared by the process of claim 1 or by an obvious chemical equivalent thereof.

3. Process according to claim 1 wherein in formula I the groups R3 and R4 together represent a double bond, and Z represents one of the divalent structures -NH-, -HN-CO-, or -N=C(OH)-.

4. Dipeptide derivatives according to claim 2 of the formula:

wherein R1, R2 and R5 have the same meaning as in formula (I) and wherein Z1 represents one of the divalent structures -NH-, -HN-CO-, or -N=C(OH)-, respectively, and pharmaceutically acceptable acid salts thereof, whenever prepared by the process of claim 3, or by an obvious chemical equivalent thereof.

5. Process according to claim 1 wherein R2 represents hydrogen, and R1 is a group R1', and R1' is chosen from an alkyl or cycloalkyl group containing up to six carbon atoms or a benzyl group.

6. Dipeptide derivatives according to claim 2 of the formula, wherein R3, R4, R5 and Z have the same meaning as in formula (I) and wherein R1' represents an alkyl or cycloalkyl radical containing up to six carbon atoms or the benzyl group and pharmaceutically acceptable acid salts thereof, whenever prepared by the process of claim 5 or by an obvious chemical equival-ent thereof.

7. Process according to claim 1 wherein R2 represents hydrogen and R1 represents a straight chain alkyl group containing one to four carbon atoms.

8. Dipeptide derivatives according to claim 2 of the formula and pharmaceutically acceptable salts thereof whenever prepared by the process of claim 7 or by an obvious chemical equivalent thereof.

9. Process for the preparation of orotyl-L-histidyl-L-proline-N-methylamide which comprises reacting together the hydrobromide of L-histidyl-L-proline-methylamide, orotic acid, and L-hydroxybenzotriazole in the pre-sence of triethylamine and N,N'-dicyclohexyl carbodiimide.

10. Orotyl-L-histidyl-L-proline-N-methylamide whenever prepared by the process of claim 9 or by an obvious chemical equivalent thereof.

11. Process for the preparation of 5-oxo-6-(D,L)-methyl-thiomorpho-line-3-(L)-carbonyl-L-histidyl-L-proline-N-methylamide which comprises react-ing together the hydrobromide of L-histidyl-L-proline methylamide, thiomorpho-line-6-(D,L)-methyl-5-on-3-(L)-carboxylic acid and 1-hydroxy benzotriazole in the presence of triethylamine and N,N'-dicyclohexyl-carbodiimide.

12. 5-Oxo-6-(D,L)-methyl-thiomorpholine-3-(L)-carbonyl-L-histidyl-L-proline-N-methylamide whenever prepared by the process of claim 11 or by an obvious chemical equivalent thereof.

13. Process for the preparation of orotyl-L-histidyl-L-proline-N(n-butyl)-amide, which comprises reacting together the hydrobromide of L-histidyl-L-proline-n-butylamide, orotic acid, and 1-hydroxybenzotriazole in the pre-sence of triethylamine and N,N'-dicyclohexyl-carbodiimide.

14. Orotyl-L-histidyl-L-proline-N-(n-butyl)-amide whenever prepared by the process of claim 13 or by an obvious chemical equivalent thereof.

15. Process for the preparation of orotyl-L-histidyl-L-proline-N-(n-hexyl)-amide which comprises reacting together the hydrobromide of L-histidyl-L-proline-(n-hexyl)-amide, orotic acid and 1-hydroxybenzotriazole in the presence of triethylamine and N,N'-dicyclohexyl-carbodiimide.

16. Orotyl-L-histidyl-L-proline-N-(n-hexyl)-amide whenever prepared by the process of claim 15 or by an obvious chemical equivalent thereof.

17. Proccss for the preparation of 5-oxo-6(D,L)-methyl-thiomorpholine 3-(L)-carbonyl-L-histidyl-L-proline-N-(n-hexyl)-amide which comprises reacting together the hydrobromide of L-histidyl-L-proline(n-hexyl) amide thiomorpholine-6-(D,L)-methyl-5-on-3-(L)-carboxylic acid and 1-hydroxy benzotriazole in the presence of triethylamine and N,N'-dicylohexyl-carbodiimide.

18. 5-Oxo-6(D,L)-methyl-thiomorpholine-3-(L)-carbonyl-L-histidyl-L-proline-N-(n-hexyl)-amide whenever prepared by the process of claim 17 or by an obvious chemical equivalent thereof.