CS237328B2 - Method of preparation of carboxyalkyldipeptide - Google Patents

Abstract

Process for preparing carboxyalkyldipeptides of general interest of Formula I SP O R | R 3, R 5, R 5 O II I I I I II R_C ~ -C-NH- ~ CH-C-N_C-C-R6 (I) I II II r2 o r7 and pharmaceutically acceptable salts thereof and biologically of the active isomer, consisting of the reaction of the amino acid derivative of formula II with a derivative of a -substituted acylamino acid of formula III. The compounds of formula I are useful as inhibitors converting enzyme and as hypertensives

Description

(54) A method for preparing carboxyalkyl dipeptides

Ϊ

A process for the preparation of carboxyalkyldipeptides of the formula I

SP

O R | R 3 R 1, R 5 O

II. I

R-C-NH-CH-C-N-CR ₆ (I)

I II II R ₂ or ₇ and pharmaceutically acceptable salts and biologically active isomer which comprises reacting the amino acid derivative of formula II with a derivative "-substituted acylamino acid of formula III.

The compounds of formula I are useful as converting enzyme inhibitors and as hypertensive agents.

The invention relates to a process for the preparation of carboxyalkyldipeptides of the formula I

OR] R ;; R ₄ R 5 O

R - C - C - NH - CH - C - N - C - C - R _c (II

I II I r ₂ or ₇ where

R ₆ and R ₆ are the same or different and are hydroxy, C 1 -C 6 alkoxy, C 1 -C 6 alkenoxy, C 1 -C 6 dialkylaminoalkoxy, C 1 -C 6 acylaminoalkoxy, and 2 to 12 carbon atoms in the acyl radical, acyloxyalkoxy of 1 to 6 carbon atoms in the alkyl radical and 2 to 12 carbon atoms in the acyl radical, aryloxy of at least 6 carbon atoms, aralkyloxy of 1 to 4 carbon atoms in the alkyl radical and at least 6 atoms aryloxy substituted with at least 6 carbon atoms or substituted aralkoxy of up to 3 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical wherein the substituent is methyl, halogen, or methoxy, amino, C 1-6 alkylamino C 1 -C 6 dialkylamino, C 1 -C 4 aralkylamino in the alkyl radical and at least 6 carbon atoms in the aryl radical or a hydroxyamino group,

R 1 is hydrogen, alkyl of 1 to 20 carbon atoms, including straight chained acyclic groups, allyl, substituted alkyl of 1 to 4 carbon atoms, wherein the substituent is halogen, hydroxy, alkoxy of 1 to 3 carbon atoms, aryloxy of at least 6 carbon atoms , amino, alkylamino, dialkylamino of 1 to 3 carbon atoms in the alkyl radical, acylamino of up to 12 carbon atoms, arylamino of at least 6 carbon atoms, and guanidino, imidazolyl, indolyl, mercapto, alkylthio of 1 to 3 carbon atoms, arylthio 6 carbon atoms, carboxy, carboxamido, C 1 -C 3 carbalkoxy, phenyl, substituted phenyl wherein the substituent is alkyl of 1 to 3 carbon atoms, phenyl, substituted phenyl wherein the substituent is alkyl of 1 to 3 carbon atoms, alkoxy 1 to 3 carbon atoms, or halogen, aralkyl of 1 to 4 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical or o indolylalkyl having 1 to 3 carbon atoms in the alkyl radical, aralkenyl having 1 to 4 carbon atoms in the alkenyl radical and at least 6 carbon atoms in the aryl radical, substituted aralkyl having 1 to 3 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical substituted indolylethyl, substituted aralkenyl of 1 to 3 carbon atoms in the alkenyl residue and at least 6 carbon atoms in the aryl residue wherein the substituent is halogen or dithiaxogen, alkyl of 1 to 3 carbon atoms, hydroxy, alkoxy of 1 to 3 carbon atoms, amino, aminomethyl, C 2 -C 12 acylamino, C 1 -C 3 dialkylamino, C 1 -C 3 alkylamino, carboxyl, C 1 -C 3 haloalkyl, cyano or sulfonamido, C 1 -C 4 aralkyl carbon atoms in the alkyl moiety and at least 6 carbon atoms in the aryl moiety or indolylethyl substituted on the alkyl moiety with amino or acylam a (C 2 -C 12) -amino group

R ₂ and R ₇ represent hydrogen, or alkyl of 1 to 6 carbon atoms,

_{R i} is hydrogen, alkyl of 1-6 carbon atoms; (C 1 -C 6) phenylalkyl, (C 1 -C 6) aminomethyl-phenylalkyl, (C 1 -C 6) hydroxyphenylalkyl, (C 1 -C 6) hydroxyalkyl, (C 1 -C 6) acetylamino, (C 1 -C 6) acylaminoalkyl C 1 -C 6 alkyl, C 1 -C 6 aminoalkyl, C 1 -C 6 dimethylaminoalkyl, C 1 -C 6 haloalkyl, C 1 -C 6 guanidinoalkyl, C 1 -C 6 imidazolyl alkyl 6 carbon atoms, C 1 -C 6 indolylalkyl, C 1 -C 6 mercaptoalkyl and C 1 -C 6 alkylthioalkyl in the alkyl radical,

R ₄ is hydrogen or alkyl of 1 to 6 carbon atoms,

_R is hydrogen, alkyl of 1-6 carbon atoms, phenyl, phenylalkyl having 1 to 6 carbon atoms, hydroxyphenylalkyl having 1 to 6 carbon atoms,., Hydroxyalkyl of 1-6 carbon atoms, aminoalkyl of 1-6 carbon atoms, guanidinoalkyl (C 1 -C 6), (C 1 -C 6) imidazolylalkyl, (C 1 -C 6) indolylalkyl, (C 1 -C 6) mercaptoalkyl or (C 1 -C 6) alkylthioalkyl, R ₄ and R ₅ are optionally combined together to form a C 2 -C 4 alkylene bridge, C 2 -C 3 alkylene bridge, C 1 -C 4 alkylene bridge or C 2 -C 4 alkylene bridge substituted with hydroxy, alkoxy with C 1 -C 6 or C 1 -C 6 alkylene and pharmaceutically acceptable salts and biologically active isomers thereof.

C 1 -C 6 alkyl or C 1 -C 6 alkenyl include, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl or vinyl, allyl, bu237328 tenyl, and the like. groups having 1 to 4 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical include, for example, benzyl, p-methoxybenzyl and the like.

Halogen means chlorine, bromine, iodine or fluorine. Aryl represents phenyl or naphthyl. Heteroaryl groups include, for example, pyrldyl, thienyl, furyl, indolyl, benzthienyl, imidazolyl and thiazolyl.

Substituted alkyl radical of substituent R1 _; R ₃ and R _c are represented as

H

_Crho-CH2 -, HS-CH ₂ -, H ₂ N- (CH _2] z, CH ₃ -S- (CH _{2) 2} -, H ₂ N- (CH _{2) 3} NH

H ₂ N - C - NH - (CH ₂ ) ₃ - and the like.

R ₄ and R ₅ , when connected by a carbon and nitrogen atom to which they are attached, form a 4- to 6-membered ring which may contain a single sulfur atom or a double bond.

Preferred rings have the general formula

wherein Y is CH ₂ , S or CHOCH _; > or formula

Preferred are compounds of formula I wherein

R is hydroxy, C 1 -C 6 alkoxy, C 1 -C 6 alkoxy, C 1 -C 4 aralkyloxy of at least 6 carbon atoms in the aryl radical, C 1 -C 6 dialkylamino group in the alkyl radical C 1 -C 6 alkoxy, C 1 -C 6 acylaminoalkoxy, C 2 -C 12 acyl, C 2 -C 12 acyloxy, C 1 -C 6 alkoxy wherein the substituent is methyl, halogen or methoxy,

R ₆ is hydroxy or amino,

R ₂ and R ₇ are hydrogen,

R ₃ is alkyl of 1 to 6 carbon atoms or aminoalkyl of 1 to 6 carbon atoms,

R ₄ and R ₅ are joined to form preferred rings as above wherein Y is CH ₂ , S or CH-OCH ₃ ,

R 1 is as defined above.

More preferred compounds are those preferred compounds of formula I wherein

R 1 is alkyl of 1 to 8 carbon atoms, substituted with alkyl of 4 to 4 carbon atoms, wherein the substituent is amino, arylthio of at least 6 carbon atoms, aryloxy of at least 6 carbon atoms or arylamino of at least 6 carbon atoms, aralkyl of 1 to 4 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical or indolylalkyl of 1 to 3 carbon atoms in the alkyl radical or substituted aralkyl (phenylalkyl or naphthylalkyl) of 1 to 4 carbon atoms in the alkyl radical and substituted indolylalkyl of 1 to 3 carbon atoms in an alkyl radical wherein the substituent (yj is halogen, dihalogen, amino, C 1 -C 6 aminoalkyl, hydroxy, C 1 -C 6 alkoxy or C 1 -C 6 alkyl.

Most preferred are compounds of formula I wherein

R is a hydroxy or alkoxy group having 1 to 6 carbon atoms,

R _e is hydroxy,

R ₂ and R ₇ are hydrogen,

R ₃ is methyl or aminoalkyl of 1 to 6 carbon atoms,

R 2 and R ₅ are joined by a carbon atom and a nitrogen atom to form proline, 4-thiaproline, or 4-methoxyproline,

R ₁ is alkyl of 1 to 18 carbon atoms, substituted alkyl of 1 to 4 carbon atoms, wherein the substituent is amino, arylthio of at least 6 carbon atoms or aryloxy and at least 6 carbon atoms or indolylalkyl of 1 to 3 carbon atoms in the alkyl radical, such as indolylethyl, or substituted (C1-C4) aralkyl (phenylalkyl or naphthylalkyl) and substituted indolylethyl, wherein the substituent (yj is halogen, dihalogen, amino, C1-C6 aminoalkyl, hydroxy, C1-C6 alkoxy); Preferred, more preferred and most preferred compounds also include pharmaceutically acceptable salts.

The compounds of the invention are useful as inhibitor of converting enzyme and as antihypertensives.

The process for the preparation of the compounds of formula I is carried out by reacting an amino acid derivative of the formula II

Ri

R — C — C — NH ₂ (II)

II I or ₂ wherein

R 1 is as defined above, including the appropriate protection of any reactive group, and R and R ₂ are as defined above, with the N-substituted acylamino acid derivative of formula III

R ₃ OR ₄ R X -CH-C-N-C-COR _e (III), r ₇ wherein X is chlorine, bromine, iodine or sulfonyloxy and R ₃ and R ₅ are as defined above and may include appropriate protection of any reactive groups and R _{1 (R 6} and R ₇ are as defined above and optionally deprotecting to give a compound of formula I wherein R and R G are as defined above except for hydroxy group, and R _b R _2, R _3, R _4, R ₅ and R ₇ are as defined above and optionally converted to R and / or R ₆ by hydrolyzing or hydrogenating the appropriate starting material for hydroxy and optionally prepare a salt thereof and, optionally, isolating the biologically more active isomer by chromatography or fractional crystallization.

The amino acid or derivative of formula II is alkylated with an appropriately substituted N -haloacetyl or α-sulfonyloxyacetylamino acid of formula III under basic conditions in water or another solvent to give compounds of formula I.

If desired, the protecting groups can be removed by known methods.

When R ₆ and R ₆ is a carboxy protecting group, such as an alkoxy or benzyloxy group thereof, it can be converted by known methods, such as hydrolysis or hydrogenation, to a compound of formula I wherein R a or R 8 is hydroxy.

The starting materials required for the above process are known in the literature or can be prepared from known starting materials by known methods.

In the products of formula (I), the carbon atoms to which R _f , R ₃ and R _{5 are} attached may be asymmetric. Thus, the compounds exist in diastereomeric forms or mixtures thereof. In the synthesis described above, racemates, enantiomers or diastereomers may be used as starting materials. substances. When di-stereoisomeric products are obtained in synthetic processes, they can be separated by conventional chromatographic methods or by fractional crystallization methods. In general, partial structures, ie.

O R,

II Γ

R-C-C-NH-R ₂

R: — — NH — CHCO — ar ₃ r ₅ o —N — C — C—

R ₇ amino acids of formula I.

The compounds of the invention form salts with various inorganic and organic acids and bases, which are also included within the scope of the invention. These salts include ammonium salts, alkali metal salts such as sodium and potassium, which are preferred, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N-methyl-D-glucamine, amino acid salts Salts with organic and inorganic acids such as HCl, HBr, H ₂ SO ₄ , H ₃ PO ₄ , methanesulfonic, toluenesulfonic, maleic, fumaric, camphorsulfonic acids can also be prepared. Non-toxic physiologically acceptable salts are preferred, although other salts are also useful, for example, in isolating or purifying the product.

Salts may be formed by conventional methods, such as by reacting the free acid or free base of the product with one or more equivalents of a suitable base or acid in a solvent or environment in which the salt is insoluble or in a solvent such as water, which is then removed under vacuum; by freeze-drying the cation of the salt present for another cation on a suitable ion exchanger.

The compounds of the invention inhibit angiotensin converting enzyme and thus block the conversion of the angiotensin I decapeptide to angiotensin II. Angiotensin II is an active substance that increases blood pressure. The blood pressure lowering effect may be derived from inhibition of its biosynthesis, particularly in animals and humans whose hypertension is affected by angiotensin II. Furthermore, the converting enzyme breaks down the vasodepressor bradycin compound. Therefore, angiotensin converting enzyme inhibitors can also lower blood pressure by potentiating bradykinin. Although the relative importance of these and other mechanisms has to be confirmed, angiotensin converting enzyme inhibitors are effective antihypertensive agents in various animal models and are clinically useful, for example, in many patients in human therapy with renovascular, malignant and essential hypertension. See, for example, D. W. Cushman et al., Biochemistry 16, 5484 (1977).

Evaluation of converting enzyme inhibitors is performed in an in vitro enzyme inhibition assay. For example, a useful method is reported by Y. Piquilloud, A. Reinharz and M. Roth, Biochem. Biophys. Acta, 206, 136 (1970), which measures the hydrolysis of carbobenzyloxyphenylalanylhistidinylleucine.

For example, in vivo evaluations are performed in normal pressure rats administered angiotensin I according to the technique of J. R. Weeks and J. A. Jones, Proc. Soc. Exp. Biol. Copper. 104, 646 (1960) or in the high renin rat model, as reported by S. Koletsky et al., Proc. Soc. Exp. Biol. Med. 125, 96 (1967).

The compounds of the invention are useful as antihypertensives in the treatment of hypertensive mammals, including humans, and can be administered to achieve blood pressure lowering by forming into compositions such as tablets, capsules, or elixirs for parenteral administration. The compounds of the invention may be administered to patients (animals and humans) in need of such treatment in a dosage range of 5 to 500 milligrams per patient when administered several times a day, with a total daily dose in the range of 5 to 2000 mg. The dose varies depending on the severity of the disease, the weight of the patient, and other factors as determined by the physician.

The compounds of the invention may also be administered in admixture with other diuretics or antihypertensives. Typical compositions are those in which the individual daily doses range from one-fifth of the minimally recommended clinical doses to the maximum recommended levels for the condition being administered individually. To illustrate these compositions, one antihypertensive agent of the invention clinically effective in the range of 15 to 200 mg per day can be effectively mixed at a level in the range of 3 to 200 mg per day with the following antihypertensive agents and diuretics over a given dose range per day:

hydrochlorothiazide (15 to 200 mg), chlorothiazide (125 to 200 mg), ethacrynic acid (15 to 200 mg), amiloride (5 to 20 mg), furosemide (5 to 80 mg), propanolol (20 to 480 mg), timolol (5 to 50 mg) and methyldopa (65 to 2000 mg). In addition, there are mixtures with three drugs such as hydrochlorothiazide (15 to 200 mg) plus amiloride (5 to 20 milligrams) + converting enzyme inhibitor according to the invention (3 to 200 mg) or hydrochlorothiazide (15 to 200 mg) + thimolol ( 5 to 50 mg) + converting enzyme inhibitor of the invention (3 to 200 mg), an effective composition for the treatment of hypertension in hypertensive patients. The above dosage range is adjusted on a unit basis as necessary to achieve a daily dose distribution.

The dose will vary depending on the severity of the disease, the weight of the patient and other factors that will be evaluated by the physician.

The above mixtures are formed into pharmaceutical preparations as described below.

About 10 to 500 mg of a compound or mixture of compounds of Formula I or a physiologically acceptable salt is admixed with a physiologically acceptable vehicle, carrier, excipient, binder, preservative, stabilizer, flavoring, etc. in unit dosage form according to accepted pharmaceutical practice. The amount of active ingredient in such compositions or compositions is such that appropriate dosages within the range will be achieved.

Examples of adjuvants that can be incorporated into tablets, capsules and the like are the following: a binder such as tragacanth, acacia, corn starch or gelatin, an excipient such as microcrystalline cellulose, a disintegrant such as corn starch, pregelatinized starch, acid alginic and the like; a glidant such as magnesium stearate; sweeteners such as sucrose, lactose or saccharin; an aromatic agent such as peppermint oil, wintergreen oil or cherry oil. When used as a unit dosage form of a capsule, it may contain, in addition to the above, a liquid carrier such as a fatty oil. Various other materials may be included as a coating or may otherwise modify the physical form of the dosage unit. For example, tablets may be coated with shellac, sugar, or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propylparaben as a preservative, a coloring agent and a flavoring such as cherry or orange essential oil.

The sterile injectable mixture may be formulated according to conventional pharmaceutical practice by dissolving or suspending the active ingredient in a vehicle, such as water for injection, a naturally occurring vegetable oil, such as sesame oil, coconut oil, peanut oil, cottonseed oil etc. or a synthetic fatty vehicle such as ethyloleate or the like. Buffers, preservatives, antioxidants and the like may be incorporated as desired.

The method according to the invention is illustrated by the following example:

Preferred diastereomers are isolated by column chromatography or traction crystallization.

Example

N-α [1- (S-carboxy-3-p-chlorophenylpropyl) -L-lysyl-L-proline

£ -3 solution ^of butoxycarbonyl-L-lysyl-L-proline (0.36 g) and 4-p-chlorophenyl-2-oxo-butyric acid (1.1 g) in 5 ml of water was treated with dilute sodium hydroxide to pH 7 and treated with 0.07 grams of sodium cyanoborohydride in 1 ml of water over several hours. After stirring overnight at room temperature, the product was adsorbed on a strongly acidic ion exchanger and eluted with 2% pyridine in water to give 0.058 g of product. The NMR spectrum indicates that the tert-Boc protecting group is not completely removed. 4.5 N HCl in ethyl acetate was added to the product, followed by isolation on an inverter, to give 0.048 g of N-, α- (1-carboxy-3-p-chlorophenylpropyl) -L-lysyl-L-proline.

The NMR and mass spectra confirm the structure. A peak at 584 is found for the silylated molecular ion. Chromatography yields the desired isomer.

Claims (1)

SUBJECT A process for the preparation of carboxyalkyldipeptides of the formula I O Rj R ₃ R ₄ Rg O R — C — C — NH — CH — C — N — C — C — R ₆ (I) I II II r ₂ or ₇ where R ₆ and R ₆ are the same or different and are hydroxy, C 1 -C 6 alkoxy, C 1 -C 6 alkenoxy, C 1 -C 6 dialkylaminoalkoxy, C 1 -C 6 acylaminoalkoxy, and 2 to 12 carbon atoms in the acyl radical, acyloxyalkoxy of 1 to 6 carbon atoms in the alkyl radical and 2 to 12 carbon atoms in the acyl radical, aryloxy of at least 6 carbon atoms, aralkyloxy of 1 to 4 carbon atoms in the alkyl radical and at least 6 atoms a substituted aryl aryloxy group of at least 6 carbon atoms or a substituted aralkoxy group of 1 to 3 carbon atoms in the alkyl group and at least 6 carbon atoms in the aryl group wherein the substituent is methyl, halogen or methoxy, amino, alkylamino of 1 to 6 atoms C 1 -C 6 dialkylamino, C 1 -C 4 aralkylamino in the alkyl radical and at least 6 carbon atoms in the aryl radical or hydroxyamino, R 1 is hydrogen, C 1 -C 20 alkyl which includes branched acyclic groups, allyl, substituted C 1 -C 4 alkyl wherein the substituent is halogen, hydroxy, C 1 -C 2 alkoxy 3 carbon atoms, aryloxy of at least 6 carbon atoms, amino, alkylamino, dialkylamino of 1 to 3 carbon atoms in the alkyl radical, acylamino of 2 to 12 carbon atoms, arylamino of at least 6 carbon atoms, and guanidino, imidazolyl, indolyl, mercapto alkylthio of 1 to 3 carbon atoms, arylthio of at least 6 carbon atoms, carboxy, carboxamido, carbalkoxy of 1 to 3 carbon atoms, phenyl, substituted phenyl, the invention wherein the substituent is alkyl of 1 to 3 carbon atoms, alkoxy of 1 to 3 atoms carbon or halogen, aralkyl having 1 to 4 carbon atoms in the alkyl radical and at least 6 carbon atoms in the aryl radical or o indolylalkyl having 1 to 3 carbon atoms in the alkyl radical, aralkenyl having 1 to 4 carbon atoms in the alkenyl radical and at least 6 carbon atoms in the aryl radical, substituted aralkyl having 1 to 3 carbon atoms in the alkyl radical and at least 6 carbon atoms in the alkyl radical aryl radical, substituted indolylethyl, substituted aralkenyl of 1 to 3 carbon atoms in the alkenyl radical and at least 6 carbon atoms in the aryl radical wherein the substituent is halogen or dihalogen, alkyl of 1 to 3 carbon atoms, hydroxy, alkoxy of 1 to 3 atoms carbon, amino, aminomethyl, C 2 -C 12 acylamino, C 1 -C 3 dialkylamino, C 1 -C 3 alkylamino, carboxyl, C 1 -C 3 haloalkyl, cyano, or sulfonamido, (C 1 -C 4) -alkyl and at least 6 aryl-aryl or indolylethyl substituted on the alkyl moiety with amino or acy a (C 2 -C 12) lamino group, R ₂ and R ₇ represent hydrogen or alkyl of 1 to 6 carbon atoms, R ₃ is hydrogen, alkyl of 1 to 6 carbon atoms, phenylalkyl of 1 to 6 carbon atoms, aminomethyl-phenylalkyl of 1 to 6 carbon atoms, hydroxyphenylalkyl of 1 to 6 carbon atoms, hydroxyalkyl of 1 to 6 carbon atoms, acetylaminoalkyl (C 1 -C 6) acylaminoalkyl (C 1 -C 6) alkyl and 2 to 12 C-acyl radicals, (C 1 -C 6) aminoalkyl, (C 1 -C 6) dimethylaminoalkyl, (C 1 -C 6) haloalkyl C 1 -C 6 guanidinoalkyl, C 1 -C 6 imidazolylalkyl, C 1 -C 6 indolylalkyl, C 1 -C 6 mercaptoalkyl and C 1 -C 6 alkylthioalkyl, R ₄ is hydrogen or alkyl of 1 to 6 carbon atoms, R ₅ is hydrogen, alkyl of 1 to 6 carbon atoms, phenyl, phenylalkyl of 1 to 6 carbon atoms, hydroxyphenylalkyl of 1 to 6 carbon atoms, hydroxyalkyl of 1 to 6 carbon atoms, aminoalkyl of 1 to 6 carbon atoms, guanidinoalkyl of 1 (C 1 -C 6), (C 1 -C 6) imidazolylalkyl, (C 1 -C 6) indolylalkyl, (C 1 -C 6) mercaptoalkyl or (C 1 -C 6) alkylthioalkyl, R ₂ and R ₅ are optionally joined together to form a C 2 -C 4 alkylene bridge, a C 2 -C 3 alkylene bridge, a C 1 -C 4 alkylene bridge or a C 2 -C 4 alkylene bridge up to 4 carbon atoms substituted by hydroxy, C1-C6 alkoxy or C1-C6 alkyl, and pharmaceutically acceptable salts and biologically active isomers thereof, characterized in that an amino acid derivative of the formula II is reacted Rj. AND R - C - C - NH ₂ (Π) or ₂ R 1 is as defined above, including the appropriate protection of any reactive group, and R and R ₂ are as defined above with the «-substituted acylamino acid derivative of the general formula III r ₃ or ₄ r ₅ X-CH-CN — C-COR ₆ (III) R ₇ where X is chlorine, bromine, iodine or sulfonyloxy and R _a and R ₅ are as defined above, which may include appropriate protection of any reactive group and R ₄ , R ₆ and R ₇ are as defined above and optionally deprotected to form a compound formula I wherein R and R ₆ are as defined above except for hydroxy and R @ _b R @ _2, R _3, R _4, R ₅ and R ₇ are as defined above and optionally converted into the R and / or R ₆ by hydrolyzing or hydrogenating the appropriate and optionally preparing a salt thereof, and optionally recovering the more biologically active isomer by chromatography or fractional crystallization.