CH624932A5 - - Google Patents

Description

The subject of the present invention is a process for the preparation of proline derivatives and related compounds of general formula I:

hs -

(ÇH) _ ÇH

H2C

co - n

* rn

!

-çh-cor in which R is a hydroxyl group, NH2 or lower alkoxy;

* *

wherein R is a hydroxyl or lower alkoxy group; R 1 is a hydrogen atom or a lower alkyl group; andn = 0.1 or 2.

In the group of compounds represented by formula II, the following subgroups are even more preferred in order (a to h) preferably increasing for the compounds which are preferred embodiments:

a) R is a hydroxyl group;

b) n = 1;

c) Rj is a hydrogen atom or a lower alkyl group;

d) Rj is a hydrogen atom or a methyl group;

e) R is a hydroxyl group, Rj is a hydrogen atom or a methyl group;

f) R is a hydroxyl group, Rj represents a hydrogen atom and n = 0;

g) R is a hydroxyl group, Rj is a hydrogen atom and n = 1;

h) R is a hydroxyl group, Rj is a methyl group and n = 1.

It will be understood that combinations of the foregoing, where applicable, are among the preferred groups.

40 Particularly preferred are stereoisomers in which proline is in the L - form.

The lower alkyl groups represented by either variant include straight or branched chain hydrocarbon groups ranging from methyl to heptyl, for example methyl, "ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl , pentyle, iso-pentyle, etc. The lower alkoxy groups are of the same kind having from 1 to 7 carbon atoms linked to oxygen, for example methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, etc. Preference is given to those in Cj-C4, in particular C1 and C2 of the two types. The phenylmethyl group is the preferred lower phenylalkyl group.

The lower alkanoyl groups are those having the acyl groups of the C2-C7 lower fatty acids, for example acetyl, 5j propionyl, butyryl, isobutyryl, etc. Likewise, lower alkanoyl groups having up to 4 carbon atoms and in particular the acetyl group are preferred.

The four common halogens are included by the term halogen, but chlorine and bromine are preferred. The substituted phenyl groups 60 preferably carry the substituent in the 4- position of the ring. The lower hydroxyalkyl groups have a hydroxyl group on an alkyl chain such as those described above, in particular on the terminal carbon atom, for example hydroxymethyl, 2-hydroxyethyl, etc. The lower aminocarboxyalkyl groups 65 have an amino group and a carboxy group on a lower alkyl group such as those described above and preferably both on a carbon atom, for example on the terminal carbon atom as in group 2- amino-2-carboxyethyl preferred.

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The products of formula I are prepared by deprotection of a corresponding derivative in which the mercapto group is protected by an acyl residue.

In general, the protected starting derivatives are prepared by acylation of a compound of formula III:

Hjc

(ch)

I I

m hn

with an acid of formula IV: R.

ck - horn

Ri r s - (ch) ■

.è n ch - cooh groupetosyloxy (CH.

SO ^ O-) or (c) a substituted acrylic acid of formula VI:

R „R,

! i1

ch = c-cooh

The product of this acylation is then subjected to a displacement or an addition with the anion of a thioacid of formula VII:

R2-SH

When the acid of formula IV is used as the acylating agent, the acylation can be carried out in the presence of a coupling agent such as dicyclohexylcarbodiimide, etc., or the acid can be activated by the formation of its anhydride mixed, symmetrical anhydride, acid chloride, acid ester or using the Woodward K reagent, N-ethoxycarbonyl-2-ethoxy-1,2,2-dihydroquinoline, etc. For an account of acylation processes, see "Methoden der Organischen Chemie" (Houven-Weyl), vol. XV, part. II, p. 1 and seq. (1974).

Compounds of formula III include for example proline, hydroxyproline, 4-methylproline, pipecolic acid, 5-hydroxypipecolic acid, azetidine-2-carboxylic acid, their lower alkyl esters, etc. The acylation of such compounds is described in more detail below.

According to a preferred process for the preparation of starting compounds, in particular when R2 is the group r5-CO, an acid or an ester of formula III is coupled with a haloalkanoic acid of formula V:

x- (ch) - ch - coch n

in which X is a halogen atom, preferably chlorine or bromine. It can be carried out by one of the known methods where the acid IV is activated before the reaction with the acid III, which involves the formation of a mixed anhydride, a symmetrical anhydride, an acid chloride , an active ester or the use of the Woodward K reagent, EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2,2-dihydroxy-quinoline), etc.

5 The product of this reaction is a compound of formula X:

h

X

(ch)

n r.

ch— co

V

(ch)

n m

-ch-cor

The product of formula X is subjected to a displacement reaction with the anion of a thioacid of formula VII:

R2-SH

in which R2 is a protective acyl group, for example an Rj-CO group in which R5 is a lower alkyl, phenyl or phenyl (lower alkyl) group.

The starting material can be prepared not only by direct acylation with an acid of formula IV, but also by intermediates such as (a) to-haloalkanoic acids of formula V:

r, r,

i i1

x- (ch) -ch-ccoh vn in which X is a bromo, chloro or iodo radical, or (b) a tosyloxyalkanoic acid, i.e. X in formula V is one for obtaining a product of formula XI:

hc— (ch) ^ 1 1 m r_ s - (ch) ch - co

2 n n - ch-cor

When R2 is the group r5-CO, we can then convert this product to product XII: ^

30 I 3

HS

I4

(ch)

I1

ch h2c

: h)

co - n

I i m

ch-cor by ammonolysis. When R is an ester group (i.e. R is a lower alkoxy group), the ester group can be removed, for example when R is a t-butoxy or t-amyloxy group by treatment of the ester. formula XI or XII with trifluoroacetic acid and anisole to obtain the corresponding free acid. When other alkoxy groups are present, alkaline hydrolysis gives the corresponding acid.

According to a variant of this process, an acrylic acid of formula 45 is used:

Ra Rt

14 11

ch = c-cooh

50 as starting material. This acrylic acid is first converted to an acid halide and then it is reacted with a compound of formula III to obtain a compound of formula XIII:

R4 R1

h2?

I3

(ch)

ch = c— co-n m

ch-cor

60 and this intermediate is subjected to the addition reaction with thioacid VII as described above.

It is also possible to use a tosyloxyalkanoic acid of formula XIV:

R, i R!

I 4 I 1

65 I I

ch3— (o) - s ° 20- (ch) - ch - cooh as agent for acylating the acid of formula III then the

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displacement reaction acylation product, etc., as described above.

Alternatively, the acrylic acid of formula VI can first be reacted with the thioacid of formula VII to obtain a product of formula XV:

r2-s-ch-ch-cooh which is converted into its acid halide, for example with thionyl chloride, then it is coupled to the compound of formula III and the same sequence is then carried out as above.

The acid or ester of formula III can also be acylated with a protected form of a to-mercaptoalkanoic acid of formula XVI:

rq-s- (ch) -ch-cooh H n in which R8 is the protective acyl group.

After the acylation, the product can be deprotected by one of the known methods mentioned above.

Further details of the preferred modes of preparation of the present compounds will be found in the following and in the examples.

According to a variant which is particularly preferred, the acid or the ester of formula III is acylated with a halo-alkanoyl halide of formula XVII:

x- (ch) —ch-cox ri in which each X is independently a halogen atom, preferably chlorine or bromine, is a hydrogen atom, a lower alkyl or lower phenylalkyl group and n = 0.1 or 2. This reaction is carried out in an alkaline medium, for example a dilute solution of alkali metal hydroxide, an alkali metal bicarbonate or a solution of alkali metal carbonate at reduced temperature, for example about 0 to 15 ° C. The reaction product is subjected to a displacement with the anion of the thioacid of formula VII above also in an alkaline medium, preferably an alkali metal carbonate solution, then it is treated in a known manner. The product of this reaction where R2 is R5-CO is converted into the product where R2 is a hydrogen atom by ammonolysis, for example an alcoholic solution of ammonia or concentrated ammonium hydroxide or by alkaline hydrolysis, for example with an aqueous hydroxide of a metal. When an acid of formula III is used as starting material, the final product obtained as free carboxylic acid can then be converted into its ester, for example by esterification with a diazoalkane such as diazomethane, a 1-alkyl-3-p -tolyltriazene such as 1-n-butyl-3-p-tolyltriazene, etc. Treatment of an ester, preferably methyl ester, with an alcoholic solution of ammonia, converts the free acid to the amide, i.e. R is NH2.

According to another variant, an ester, preferably the t-butylester of formula III, is treated in an anhydrous medium such as dichloromethane, tetrahydrofuran, dioxane, etc. with a thioalkanoic acid of formula XVIII:

r -s- (ch) ch cooh

2. 2 n in the presence of dicyclohexylcarbodiimide, N, N'-carbonylbis-imidazole, ethoxyacetylene, diphenylphosphoryl azide or analogous coupling agents at a temperature between about 0 and 10 ° C. The can then be removed ester group R, for example by treatment with trifluoroacetic acid and anisole at approximately room temperature.

The products of formula I have one or more asymmetric carbon atoms. When Rj, R3 or R4 is other than hydrogen, the carbon atom to which it is attached is asymmetric. These carbon atoms are indicated by an asterisk in the formula I. Thus, the compounds exist in stereoisomeric forms or in their racemic mixtures. All of these are within the scope of the invention. The synthesis described above can use the racemate or one of the enantiomers as starting material. When the racemic product is used as a starting material for the synthesis process, the stereoisomers obtained in the product can be separated by conventional methods of chromatography or fractional crystallization. In general, the L— isomer relative to the carbon atom of the amino acid represents the preferred isomer form. The D- isomer is also preferred over the carbon atom a in the acyl side chain (i.e., the carbon atom bearing R 1).

The present compounds form basic salts with various inorganic and organic bases which are also within the scope of the invention. These salts include ammonium salts, alkali metal salts such as the preferred sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with bases organic, for example the dicyclohexylamine salt, the benzathine, N-methyl-D-glucamine, dTiydrabamine salts, salts with amino acids such as arginine, lysine, etc. Physiologically acceptable non-toxic salts are preferred although other salts are also useful, for example for isolating or purifying the product as illustrated in the examples in the case of the dicyclohexylamine salt.

The salts are formed in known manner by reacting the product in the form of free acid with one or more equivalents of the appropriate base providing the desired cation in a solvent or a medium in which the salt is insoluble or in water, then by separating the water by lyophilization. By neutralization of the salt with an insoluble acid such as a cation exchange resin in hydrogen form (for example, a polystyrene-sulfonic acid resin such as Dowex 50) or with an aqueous acid and then extraction with an organic solvent, by For example ethyl acetate, dichloromethane, etc., the product can be obtained in the form of free acid and, if desired, form another salt.

Further experimental details are found in the examples which are preferred embodiments and which also serve as a model for the preparation of other group members.

The present compounds inhibit the conversion of the decapeptide which is angiotensin I into angiotensin II and therefore they are useful for reducing or relieving hypertension in relation to angiotensin. The action of renin which is an enzyme on angiotensinogen which is a pseudoglobulin in the blood plasma, produces angiotensin I. Angiotensin I is converted by an enzyme converting angiotensin (ACE) into angiotensin II. The latter is a hypotensive substance that has been implicated as the causative agent of various forms of hypertension in various species of mammals, for example rats and dogs. The present compounds intervene in the sequence angiotensin (renin) - »angiotensin I-> angiotensin II by inhibiting the enzyme which converts angiotensin and by reducing or suppressing the formation of angiotensin II which is a substance which is a hypotensive . Thus, by the administration of a composition containing one or more of the compounds of formula I or one of their physiologically acceptable salts, the hypertension which depends on angiotensin in the mammalian species which suffer from it is relieved. A single dose or preferably two to four daily shared doses given at about 0.1 to 100 mg / kg / day and preferably 1 to 50 mg / kg / day are suitable for reducing blood pressure as indicated in the experiments on animal models described by SL Engel, TR Schaeffer, MH Waugh and B. Rubin, “Proc. Soc. Exp. Biol. Med. ”, 143.483 (1973). Preferably, the substance is administered orally, but parenteral routes can also be used.

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such as the subcutaneous, intramuscular, intravenous or intraperitoneal route.

The present compounds can be used to obtain the reduction of blood pressure by putting them into composition for forms such as tablets, capsules or elixirs for oral administration or in sterile solution or suspension for parenteral administration. Approximately 10 to 500 mg of a compound or a mixture of compounds of formula I or their physiologically acceptable salt is made up with a vehicle, an excipient, a binding agent, a preservative, a stabilizing agent, a flavor , etc., physiologically acceptable in a unit dose form satisfying established pharmaceutical practice. The amount of active substance in these compositions or preparations is such that an appropriate dose in the range indicated is obtained.

Examples of adjuvants that can be incorporated into tablets, capsules, etc. are as follows: a binding agent such as tragacanth, acacia, corn starch or gelatin; an excipient such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid, etc. ; a lubricating agent such as magnesium stearate; a sweetening agent such as sucrose, lactose or saccharin; an aroma such as the essence of peppermint, the essence of wintergreen or cherry. When the unit dose form is a capsule, it may contain, in addition to the abovementioned substances, a liquid vehicle such as a fatty oil. Various other substances may be present as coatings or to otherwise modify the physical form of the dose unit. For example, the tablets can be coated with shellac, sugar or both. A syrup or an elixir may contain the active compound, sucrose as a sweetening agent, methyl and propyl paraben as a preservative, a color and an aroma such as that of cherry or orange.

Sterile compositions can be prepared for injection according to established pharmaceutical practice by dissolving or suspending the active substance in a vehicle such as water for injection, a natural vegetable oil such as sesame oil, coconut oil, peanut oil, cottonseed oil, etc., or a synthetic fatty vehicle such as ethyl oleate, etc. Buffering agents, preservatives, antioxidants, etc. can be incorporated as required.

The following examples illustrate the invention. All temperatures are in degrees centigrade. The examples, the number of which is followed by an asterisk, relate to the preparation of the starting compound.

Example 1 *:

l- (2-benzoylthioacétyi) -Lproline

5.75 g of L-proline are dissolved in 50 ml of sodium hydroxide N and the solution is cooled in an ice-water bath. 26 ml of 2N sodium hydroxide and 5.65 g of chloroacetyl chloride are added, then the mixture is vigorously stirred at room temperature for 3 h. A suspension of 7.5 g of thiobenzoic acid and 4.8 g of potassium carbonate in 50 ml of water is added. After 18 h of stirring at room temperature, the reaction mixture is acidified and extracted with ethyl acetate. The ethyl acetate layer is washed with water, dried over magnesium sulfate and concentrated to dryness in vacuo. The 14.6 g of residue are dissolved in 150 ml of ethyl acetate and 11 ml of dicyclohexylamine are added. The crystals are filtered and recrystallized from ethyl acetate to obtain 5.7 g which melts at 151-52 ° C. To convert the salt to the acid, the crystals are dissolved in a mixture of 100 ml of 5% aqueous potassium bisulfate and 300 ml of ethyl acetate. The organic phase is washed once with water, dried over magnesium sulfate and concentrated to dryness under vacuum to obtain 3.45 g.

Example 2:

l- (2-mercaptoacetyl) -L-proline

3.4 g of 1- (2-benzoylthioacetyl) -L-proline are dissolved in a mixture of 10.5 ml of water and 6.4 ml of concentrated ammonia. After 1 h, the reaction mixture is diluted with water and then filtered. The filtrate is extracted with ethyl acetate and then acidified with concentrated hydrochloric acid, saturated with sodium chloride and extracted twice with ethyl acetate. The ethyl acetate extracts are washed with saturated sodium chloride and concentrated to dryness to give 1.5 g. The product, i.e. 1- (2-mercapto-acetyl) -L-proline, is crystallized from ethyl acetate; it melts at 133-135 ° C.

Example 3 *:

1 - [2-Benzoylthioacetyl) -Lproline methyl ester The l- (2-benzoylthioacetyl) -L-proline obtained in Example 1 is dissolved in methanol and an ethereal solution of diazomethane is added until there is has a persistent yellow color. After 15 min a few drops of acetic acid are added and the solvent is removed in vacuo to obtain the methyl ester of 1- (2-benzoylthioacetyl) -L-proline.

Example 4:

1- (2-Mercaptoacetyl) -Lrproline amide The product of Example 3 is dissolved in 10% methanolic ammonia and the solution is kept at room temperature in a pressure-supporting bottle. When the analysis by thin layer chromatography indicates that the two ester functions are ammonolysed, the reaction mixture is concentrated to dryness to obtain the amide of 1- (2-mercaptoacetyl) -L-proline.

Example 5 *:

l- (2-benzoylthioacetyl) -Irhydroxyproline By substituting L-hydroxyproline for L-proline in the process of Example 1, l- {2-benzoylthioacetyl) -L-hydroxyproline is obtained.

Example 6:

l- (2-mercaptoacetyl) -Lrhydroxyproline

By treating the product of Example 5 with ammonia as in Example 2, we obtain l- (2-mercaptoacetyl) -L-hydroxyproline.

Example 7 *:

Acid 1 - (2-benzoylthioacétyî) -Lazétidine-2-carboxylic

By substituting L-azetidine-2-carboxylic acid for L-proline in the process of Example 1, the acid is obtained

1- (2-benzoylthioacetyl) -L-azetidine-2-carboxylic.

Example 8:

Acid 1 - (2-mercaptoacétyî) -Lazétidine-2-carboxylic By treating the product of example 7 with ammonia as in example 2, one obtains acid 1 - (2-mercaptoacétyl) -L-azétidine -

2-carboxylic.

Example 9 *:

1 - (2-Benzoylthioacetyl) -Lpipecolic acid By substituting L-pipecolic acid for L-proline in the process of Example 1, l- (2-benzoylthioacetyl) -L-pipecolic acid is obtained.

Example 10:

1 - (2-Mercaptoacetyl) -Lpipecolic acid By treating the product of Example 9 with ammonia as in Example 2, we obtain l- (2-mercaptoacetyl) -L-pipecolic acid.

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Example 11 *:

l- (2-benzoylthiopropanoyl) -Lproline 5.75 g of L-proline is dissolved in 50 ml of aqueous sodium hydroxide N and the solution is refrigerated in an ice bath with stirring. 25 ml of 2N sodium hydroxide and 8.57 g of 2-bromopropionyl chloride are added in this order and the mixture is removed from the ice bath and stirred at room temperature for 1 h. A mixture of 7.5 g of thiobenzoic acid and 4.8 g of potassium carbonate in 50 ml of water is added and the mixture is stirred overnight at room temperature. After acidification with concentrated hydrochloric acid, the aqueous solution is extracted with ethyl acetate and the organic phase is washed with water, dried and concentrated to dryness. The 14.7 g of residue is chromatographed on a 440 g of silica gel column with a 7: 1 mixture of benzene: acetic acid. The fractions containing the desired substance are combined, concentrated to dryness and the residue is precipitated twice with etherhexane and it is converted to a dicyclohexylamine salt in etherhexane and 9.4 g are obtained which melt at (142) 148-156 ° C. The dicyclohexylamine salt is reconverted to the acid as in Example 1 and 5.7 g are obtained.

Example 12:

l- [2-mercaptopropanoyl) -Lproline

5.7 g of 1- (2-benzoylthiopropanoyl) -L-proline are dissolved in a mixture of 12 ml of water and 9 ml of concentrated ammonium hydroxide with stirring. After 1 h, the mixture is diluted with 10 ml of water and filtered. The filtrate is extracted twice with ethyl acetate, it is concentrated to one third of the original volume, it is acidified with concentrated hydrochloric acid and it is extracted with ethyl acetate. The organic phase is washed with saturated sodium chloride, dried and concentrated to dryness under vacuum. The residue is crystallized, that is to say l- (2-mercaptopropanoyl) -L-proline from a mixture of ethyl acetate and hexane and 3 g are obtained which melt ( 105) at 116-120 ° C.

Example 13 *:

l- (3-benzoylthiopropanoyl) -Lproline 5.75 g of L-proline is dissolved in 50 ml of normal sodium hydroxide and the solution is refrigerated in an ice bath. 8.5 g of 3-bromopropionyl chloride and 27 ml of 2N sodium hydroxide are added and the mixture is stirred for 10 min in the ice bath and then 3 h at room temperature. A suspension of 7.5 g of thiobenzoic acid and 4.5 g of potassium carbonate in 50 ml of water is added and the mixture is stirred for 18 h at room temperature. After acidification with concentrated hydrochloric acid, the aqueous phase is extracted twice with ethyl acetate. The organic layers are dried over magnesium sulphate and concentrated to dryness under vacuum to obtain l- (3-benzoylthiopropanoyl) -L-proline; 7.1 g are obtained which melts at 101-102 ° C (ethyl acetatehexane).

Example 14 *:

L-proline tert-butylester

230 g of L-proline are dissolved in a mixture of 11 of water and 400 ml of 5N sodium hydroxide. The solution is refrigerated in an ice bath and then, with vigorous stirring, 460 ml of 5N sodium hydroxide and 340 ml of benzyloxycarbonyl chloride are added in five aliquots in the course of 1 h. After stirring for 1 hour at room temperature, the mixture is extracted twice with ether and acidified with concentrated hydrochloric acid. The precipitate is filtered and dried. 442 g are obtained, which melts at 78-80 ° C.

The 180 g of the benzyloxycarbonyl-L-proline thus obtained are dissolved in a mixture of 300 ml of dichloromethane, 800 ml of liquid isobutylene and 7.2 ml of concentrated sulfuric acid. The solution is stirred in a pressure bottle for 72 h. The pressure is released, the isobutylene is allowed to evaporate and the solution is washed with 5% sodium carbonate, water, dried over magnesium sulfate and concentrated to dryness under vacuum to obtain 205 g of benzyloxycarbonyl-L-proline t-butyl ester.

205 g of benzyloxycarbonyl-L-proline t-butyl ester are dissolved in 1.21 of absolute ethanol and hydrogenated at normal pressure with 10 g of 10% palladium on carbon until only one is observed. trace of carbon dioxide in hydrogen which is the exit gas (24 h). The catalyst is filtered off and the filtrate is concentrated in vacuo to 30 mm Hg. The residue is distilled in vacuo to obtain the L-proline t-butyl ester which boils at 50-51 ° C / l mm.

Example 15 *:

1- (3-acetylthiopropanoyl) -Lproline tert-butyl ester 5.13 g of L-proline t-butylester is dissolved in 40 ml of dichloromethane and the solution is refrigerated in an ice-water bath. A solution of 6.18 g of dicyclohexylcarbodi-imide in 20 ml of dichloromethane is added and then immediately 4.45 g of 3-acetylthiopropionic acid are added. After 15 minutes of stirring in the ice-water bath and 16 hours at ordinary temperature, the precipitate is separated by filtration and the filtrate is concentrated to dryness under vacuum. The residue is dissolved in ethyl acetate and washed until neutral. The organic layer is dried over magnesium sulfate and concentrated to dryness in vacuo to obtain 9.8 g of 1- (3-acetylthiopropanoyl) -L-proline t-butylester.

Example 16 *:

l- {3-acetylthiopropanoyî) -Lproline

4.7 g of 1- (3-acetylthiopropanoyl) -L-proline t-butyl ester are dissolved in a mixture of 34 ml of anisole and 68 ml of trifluoroacetic acid and the mixture is kept at room temperature for 1 hr. The solvents are removed in vacuo and the network is precipitated from etherhexane several times. The 3.5 g of residue is dissolved in 25 ml of acetonitrile and 2.8 ml of dicyclohexylamine are added. The crystalline salt is filtered and recrystallized from isopropanol. 3.8 g are obtained, which melts at 176-177 ° C. The salt is reconverted into 1- (3-acetylthiopropanoyl) -L-proline as in Example 1 and 1.25 g are obtained which melts at 89-90 ° C (ethyl acetatehexane).

Example 17:

l- (3-mercaptopropanoyl) -Lproline Method A

4.9 g of l- (3-benzoylthiopropanoyl) -L-proline are dissolved in a mixture of 8 ml of water and 5.6 ml of concentrated ammonium hydroxide and the solution is kept with stirring under argon for 1 h. The reaction mixture is diluted with water, filtered and the filtrate is extracted with ethyl acetate. The aqueous phase is acidified with concentrated hydrochloric acid, saturated with sodium chloride and extracted with ethyl acetate. The organic layers are washed with saturated sodium chloride, dried over magnesium sulfate and concentrated to dryness in vacuo. The residue is crystallized, that is to say l- (3-mercaptopropanoyl) -L-proline from ethyl acetate and hexane and 2.5 g are obtained which melt at 68- 70 ° C.

Method B

0.8 g of 1- (3-acetylthiopropanoyl) -L-proline is dissolved in 5 ml of 5.5M methanolic ammonia and the solution is kept under argon at room temperature. After 2 h, the solvent is removed under vacuum, the residue is dissolved in water and it is applied to an ion exchange column on the M + cycle (Dowex 50, analytical grade) and it is eluted with l 'water. The fractions which give a positive thiol reaction are combined and concentrated to dryness to obtain 0.6 g. This product is crystallized from ethylhexane acetate as in process A to obtain l- (3-mercapto-propanoyl) -L-proline.

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Salts: 15 ml of dichloromethane then a solution is immediately added

- sodium tion of 4.9 g of 3-acetylthio-2-methylpropanoic acid in 5 ml of ^, dichloromethane. After having stirred for 15 min in the bath, 500 mg of l- (3-mer "ptopropanoyl) -L-prohne are dissolved in, ace and 16 h at ordinary temperature, the precipitate is separated by a mixture of 2.5 ml of water. and 2.5 ml of sodium hydroxide N. Filtration is carried out and Qn is concentrated to dryness under vacuum, the filtrate Qn dissolves the residue lyophilizes the solution to obtain the sodium salt. dam racète d> fthyte e {Qn laye until neutral. Qn dry it

- magnesium organic phase over magnesium sulfate and concentrated to dryness under vacuum. The residue, that is to say the t-butylester, is purified. 500 mg of l- (3-mercaptopropanoyl) -L-proline, 49.5 mg u3.acetylthio.2-methylpropanoyl) -L-proline is stirred by chromatography. -

magnesium oxide and 10 ml of water by heating slightly IQ made on a column (silicagei.chloroform) and we obtain 7.9 g. until complete dissolution. Then the solvent is removed by lyophilization to obtain the magnesium salt. Example 23 *:

- calcium 1- (3-acetylthio-2-methylpropanoyî) -Lproline

Method A

500 mg of 1- (3-mercaptopropanoyl) -2-proline are dissolved in [5 Qn dissolved? g of t.but lester of i. (3.acetylthio-2-methyl-

a mixture of 91 mg of calcium hydroxide and 10 ml of water then propanoyl) _L-proline from Example 23 in a 55 ml mixture lyophilizes the solution to obtain the calcium salt. of anisole and 111 ml of triflUOroacetic acid. After keeping

- of potassium for 1 h at ordinary temperature, the solvent is separated under vacuum and the residue is precipitated several times from etherhexane.

500 mg of 1- (3-mercaptopropanoyl) -L-prol 2Q Qn are dissolved, the 6 g of residue is dissolved in 40 ml of acetonitrile, and 246 mg of potassium bicarbonate and 10 ml of 45 ml are added to a mixture. dicyciohexylamine. The crystal salt is boiled with water and lyophilized to obtain the potassium salt. 1 (X) ml of fresh acetonitrile, refrigerate to room temperature

N-methyl-D-glucamine and filter to obtain 3.8 g which melts (165) at 187-188 ° C.

This substance is recrystallized from isopropanol. She has one

500 mg of 1- (3-mercaptopropanoyl) -L-proline and the value [a] _ 6? 0 (c 1A EtOH) are dissolved. The salt is suspended

480 mg of N-methyl-D-glucamine in 10 ml of water and the crystalline dicyclohexylamine is lyophilized in a mixture of bis-sulfate to obtain the salt of N-methyl-D-glucamine. 5% aqueous potassium and ethyl acetate. We wash the phase

Example 18: organic with water and concentrated to dryness. The residue l- [3-mercaptopropanoyl) -Lhydroxyproline is crystallized from ethyl acetate hexane to obtain l- (3-acetylthio-2-D-

30 methylpropanoyl) -L-proline which melts at 83-85 C and has a value

By substituting L-hydroxyproline for L-proline in [a] 25 = —162 (c 1 7 EtOH)

process of example 11 then by treating the product by process A

from Example 17, we obtain l- (3-benzoylthiopropanoyl) -L- Method B

hydroxyproline and l- (3-mercaptopropanoyl) -L-hydroxyproIine Qn mixture 8> 1 g of 3-acetylthio-2-methylpropanoic acid respectively. 35 and 7 g of thionyl chloride, then the suspension is stirred for

Example 19: 4:00 p.m. at room temperature. The reaction mixture is concentrated to dryness

,, j \ r ru i> tional and distilled under vacuum (m.p. = 80 ° C). The 5.4 g of

143-mercaptopropanoylyl * azetidine-2-carboxylic acid. ,,. . ,. '„, 1.,

x this 3-acetylthio-2-methylpropanoic acid chloride and 15 ml

By substituting the t-butyl ester of L-azetidine-2-carbon 2N sodium hydroxide for a solution of 3.45 g of L-proline xylic acid (prepared by substitution of L-azetidine-2- acid carboxy- 4Q in 30 ml of normal sodium hydroxide refrigerated in a bath

Iic with proline in Example 14) with t-butyl ester of L-proline in ice water. After stirring for 3 h at room temperature

in the process of example 15, by treating the product as in naire> the mixture is extracted with ether, the aqueous phase is acidified and example 16 and the acid l- (3-acetylthiopropanoyl) -L-azetidine -2-carb- is extracted with ethyl racetate. The organic phase is dried on oxylic thus obtained by method B of Example 17, the magnesium sulphide is obtained and it is concentrated to dryness to obtain the t-butyl ester of l- (3-acetylthiopropanoyl) acid. -L-azetidine-2-45 ^ s.acetylthio ^ -DL-methylpropanoylj-L-proline.

carboxylic acid and l- (3-mercaptopropanoyl) -L-azetidine-2-

carboxylic respectively. Method C

EXAMPLE 20 4.16 g of methacryloyl chloride are added to a solution of

L-Ç-mercaptopropanoyîi-Lpipécolique j5'45 ® of L-proline in a mixture of 100 ml of water and 12 g of

50 sodium bicarbonate refrigerated in an ice and water bath

By substituting the t-butyl ester of L-pipecolic acid (prepared by vigorous stirring. When the addition is complete, the substituent L-pipecolic acid is stirred for L-proline in Example 14) mixture at temperature ordinary for 2 h then it is extracted at

with L-proline t-butylester in the process of Example 15 and with ether. The aqueous phase is acidified with hydrochloric acid N

treating the product by method C of Example 17, the product is obtained and extracted with ethyl acetate. The t- butyl ester of 1- (3-mercaptopropanoyl) -L-pipecolic acid and organic phase are concentrated to dryness under vacuum and the organic phase is mixed with 3.5 g of thiol acid.

1- (3-mercaptopropanoyl) -L-pipecolic acid respectively. acetic, add a few crystals of azobisisobutyronitrile and

Example 21:

heat the mixture in a water bath for 2 h. The reaction mixture is dissolved in a 75:25 mixture of benzene-acetic acid and 1 - (3-mercaptopropanoyl) -4-methyl-Lprolinè is applied to a column of silica gel. Elution with the same mixture

Substituting 4-methyl-L-proline for L-proline in the solvent <> <> gives the 1- (3-acetylthio-2-DL-methylpropanoyl) -L-process of Example 13 then treating the product by process A proline.

from Example 17, l- (3-benzoylthiopropanoyl) -L-proline is obtained. gxempje 24 *

Example 22 *: ;-( 3-benzoylthio-2-methylpropanoyl) -Lproline tert-butyl ester of l- (3-acetylthio-2-methylpropanoyl) -Lproline 55 By substituting the t-butyl ester of l- (3-benzoylthio-2 -methyl-5.1 g of L-proline t-butylester are dissolved in 40 ml of propanoyl) -L-proline with 1- (3-acetylthio-2- t-butylester)

dichloromethane and the solution is stirred and refrigerated in a methylpropanoyl) -L-proline bath in process A of Example 23, ice is obtained. 6.2 g of dicyclohexylcarbodiimide dissolved in gives l- (3-benzoylthio-2-methylpropanoyl) -L-proline are added.

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Example 25 *:

l- (3-phenylacetylthio-2-methylpropanoy1) -Lrproline By substituting the t-butylester of 1 - (3-phenylacetylthio-2-methyl-propanoyl) -L-proline for the t-butylester of l- (3-acetylthio-2 -methyl-propanoyl) -L-proline in process A of Example 23, 1 - {3-phenylacetylthio-2-methylpropanoyl) -L-proline is obtained.

Example 26:

l- (3-mercapto-2-D-methylpropanoyl) -Lproline The l- (3-mercapto-2-methylpropanoyl) -L-proline is obtained by treating the product of each of Examples 23, 24 and 25 as follows:

0.85 g of the thioester is dissolved in 5.5N methanolic ammonia and the solution is kept at room temperature for 2 h. The solvent is removed in vacuo and the residue is dissolved in water, applied to an ion exchange column on the H + cycle (Dowex 50, analytical grade) and eluted with water. The fractions which give a positive thiol reaction are combined and lyophilized. The residue is crystallized from ethyl acetate hexane and 0.3 g is obtained. 1- (3-mercapto-2-D-methylpropanoyl) -L-proline melts at 103-104 ° C and has a value [oc] D = -131 (C, 2, EtOH).

Example 21:

l- {3-mercapto-2-benzylpropanoyl) -Lproline The l- (3-acetylthio-2-benzylpropanoyl) -L-proline is treated with methanolic ammonia according to the method of Example 26 to obtain l- ( 3-mercapto-2-benzylpropanoyl) -L-proline in the form of an oil which has an Rf value = 0.47 (silica gel, 15:25 mixture of benzene: acetic acid).

Example 28:

l- {3-mercapto-2-methylpropanoyl) -Lhydroxyproline By substituting the t-butylester t-butyl ether of L-hydroxyproline in the process of example 22, by treating the product according to process A of example 23 and then continuing as in Example 26, the t-butyl ester of 1- (3-acetylthio-2-methyl-propanoyl) -L-hydroxyproline is obtained, the t-butyl ether of 1- (3-acetylthio-2-methylpropanoyl) - L-hydroxyproline and 1- (3-mercapto-2-methyl-propanoyl) -L-hydroxyproline respectively.

Example 29:

1- (3-mercapto-2-methylpropanoyl) -L, azetidine-2-carboxylic acid

By substituting the t-butyl ester of L-azetidine-2-carboxy-lique in the process of example 22, by treating the product according to process A of example 23 then while continuing as in example 26, we obtain the t-butyl ester of 1- (3-acetylthio-2-methylpropanoyl) -L-azetidine-2-carboxylic acid, 1,3-acetyl-thio-2-methylpropanoyl) -L-azetidine-2 -carboxylic and 1 - (3-mercapto-2-methylpropanoyl) -L-azetidine-2-carboxylic acid.

Example 30:

Acid 1 - (3-mercapto-2-methylPropanoyï) -Lpipécolique By substituting L-pipecolic acid in the process of example 22, by treating the product according to process A of example 23 then by continuing as in l example 26, the t-butyl ester of l- (3-acetylthio-2-methylpropanoyl) -L-pipecolic acid, l- (3-acetylthio-2-methylpropanoyl) -L-pipecolic acid and l- (3-mercapto-2-methylpropanoy]) - L-pipecolic acid respectively.

Example 31 *:

l- {4-benzoylthiobutanoyl) -Lproline

To a solution of 2.88 g of L-proline in 25 ml of normal sodium hydroxide refrigerated in an ice bath, 12.5 ml of 2N sodium hydroxide and 3.5 g of 4- chloride are added. chlorobutyryl.

The reaction mixture is stirred at room temperature for 3 h and a suspension of 3.75 g of thiobenzoic acid and 2.4 g of potassium carbonate in 25 ml of water is added. After stirring overnight at room temperature, the reaction mixture is acidified with concentrated hydrochloric acid and extracted with ethyl acetate. The organic layer is dried over magnesium sulfate and concentrated to dryness in vacuo. The residue is chromatographed on a silica gel column with a 7: 1 mixture of benzene: acetic acid. The fractions containing the desired substance are combined and concentrated to dryness to obtain 1.35 g. A small aliquot of this substance is dissolved in ethyl acetate and dicyclohexylamine is added until pH = 6 to 10 (on wet paper at pH). The dicyclohexylamine salt separates by crystallization immediately. It melts at 159-161 ° C.

Example 32:

1 - {4-mercaptobutanoyî) -Lproline

1.08 g of 1- (4-benzylthiobutanoyl) -L-proline are dissolved in a mixture of 4 ml of water and 2.7 ml of concentrated ammonia. After stirring for 1 hour at room temperature, the mixture is diluted with water, filtered, extracted with ethyl acetate and the aqueous phase is concentrated in vacuo. This ammonium salt of 1- (4-mercaptobutanoyl) -L-proline is purified by ion exchange chromatography on a column of diethylaminoethyl-Sephadex (crosslinked dextran) with a gradient of ammonium bicarbonate; 0.7 g is obtained. The ammonium salt is dissolved in 2 ml of water and applied to a column of Dowex 50 sulfonic acid resin of analytical grade in H + form and the free acid is eluted with water. The fractions containing the desired substance (positive towards the sulfhydryl reagent and the carboxyl reagent) are combined and lyophilized to obtain l- (4-mercaptobutanoyl) -L-proline. The dicyclohexylammonium salt is prepared by the method of Example 32; it melts at 157-158 ° C.

Example 33 *:

With 4-bromo-2-methylbutanoic acid

1.04 g of ethyl 4-bromo-2-methylbutanoate [G. Jones and J. Wood, “Tetrahedron”, 21, 2961 (1965)] in 50 ml of dichloromethane and the mixture is cooled to -10 ° C. A 1M solution of boron tribromide in dichloromethane is added dropwise (50 ml) and stirring is continued for 1 h at -10 ° C and 2 h at 25 ° C. The reaction is terminated by carefully adding water. The layers are separated and the organic phase is washed with water, dried and concentrated to dryness to obtain 4-bromo-2-methylbutanoic acid.

Example 34 *:

l- {4-benzoylthio-2-methylbutanoyl) -L, proline a) 8 g of 4-bromo-2-methylbutanoic acid and 7 g of thionyl chloride are mixed and the mixture is stirred for 16 h at room temperature . The reaction mixture is concentrated to dryness and distilled in vacuo.

b) To a solution of 2.88 g of L-proline in 25 ml of normal sodium hydroxide refrigerated in an ice bath, 12.5 ml of 2N sodium hydroxide and 3.9 g of chloride D are added. 4-bromo-2-methylbutanoic acid obtained in step a). The reaction mixture is stirred at room temperature for 3 h and a suspension of 3.75 g of thiobenzoic acid and 2.4 g of potassium carbonate in 25 ml of water is added. After stirring overnight at room temperature, the mixture is acidified with concentrated hydrochloric acid and extracted with ethyl acetate. The organic layer is dried over magnesium sulfate and concentrated to dryness in vacuo. The residue is chromatographed on a silica gel column with a 7: 1 mixture of benzene: acetic acid. The fractions containing the desired product, that is to say 1 - (4-benzoyl-thio-2-methylbutanoyl) -L-proline, are combined and concentrated to dryness under vacuum.

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Example 35:

l- (4-mercapto-2-methylbutanoyl) -L-proline

By substituting l- (4-benzoylthio-2-methylbutanoyl) -L-proline for l- (4-benzoylthiobutanoyl) -L-proline in the process of Example 32, l- (4-mercapto- 2-methylbutanoyl) -L-proline.

Example 36 *:

4-bromo-2-benzylbutanoic acid By substituting ethyl 4-bromo-2-benzylbutanoate (prepared by the method of G. Jones and J. Wood "Tetrahedron", 21, 2961 (1965), starting with benzylmalonate diethyl) with 4-bromo-

Ethyl 2-methylbutanoate in the process of Example 34, 4-bromo-2-benzylbutanoic acid is obtained.

Example 37 *:

l- {4-benzoylthio-2-benzylbutanoyl) -Lproline By substituting 4-bromo-2-benzylbutanoic acid for 4-bromo-2-methylbutanoic acid in the process of Example 35, the l- (4-benzoylthio-2-benzylbutanoyl) -L-proline.

Example 38:

l- (4-mercapto-2-benzylbutanoyï) -Lproline By substituting l- (4-benzoylthio-2-benzylbutanoyl) -L-proline for l- (4-benzoylthiobutanoyl) -L-proline in the process of Example 32, l- (4-mercapto-2-benzylbutanoyl) -L-proline is obtained.

Example 39:

l- (4-mercaptobutanoyl) -Lhydroxyproline By substituting L-hydroxyproline for L-proline in the process of example 31 and by subjecting the product to ammo-nolysis as in example 32, one obtains l- (4-benzoylthio-butanoyl) -L-hydroxyproline and 1- (4-mercaptobutanoyl) -L-hydroxyproline respectively.

Example 40:

1 - (4-mercaptobutanoyl) -Lazetidine-2-carboxylic acid By substituting L-azetidine-2-carboxylic acid for L-proline in the process of Example 31 and subjecting the product to ammonolysis as in l Example 32, l- (4-benzoylthiobutanoyl) -L-azetidine-2-carboxylic acid and 1 - (4-mercaptobutanoyl) -L-azetidine-2-carboxylic acid, respectively, are obtained.

Example 41:

Acid 1 - (4-mercaptobutanoyl) -Lpipecolic By substituting L-pipecolic acid for L-proline in the process of Example 31 and subjecting the product to ammonolysis as in Example 32, the l- (4-benzoylthio-butanoyl) -L-pipecolic acid and 1- (4-mercaptobutanoy I) -L-pipecolic acid respectively.

Example 42 *:

l- (3-acetylthiobutanoyî) -LProline tert-butylester 6.2 g of dicyclohexylcarbodiimide and 4.86 g of acid are added

3-acetylthiobutyric acid to a solution of 5.1 g of L-proline t-butyl ester in 60 ml of dichloromethane stirred in an ice bath. After 15 min, the ice bath is removed and the mixture is stirred at room temperature for 16 h. The precipitate is filtered, the filtrate is concentrated to dryness and the residue is chromatographed on a silica gel column with chloroform to give 5.2 g of 1- (3-acetylthiobutanoyl) -L-proline t-butyl ester.

Example 43 *:

l- (3-acetylthiobutanoyt) -Lproline

The 5.2 g of 1- (3-acetylthiobutanoyl) t-butylester are dissolved -

L-proline from Example 42 in a mixture of 60 ml of tri-fluroacetic acid and 30 ml of anisole and the solution is kept at room temperature for 1 h. The solvents are separated in vacuo and the residual l- (3-acetylthiobutanoyl) -L-proline is reprecipitated from etherhexane several times to obtain 4 g. The dicyclohexylamine salt is prepared by the method of Example 31, it melts at 175-176 ° C.

Example 44:

l- {3-mercaptobutanoyî) -Lproline

0.86 g of the 1- (3-acetylthiobutanoyl) -L-proline of Example 43 is dissolved in 20 ml of 5.5N methanolic ammonia and the reaction mixture is kept at room temperature for 2 h. The solvent is removed in vacuo and the residue is chromatographed on an ion exchange column (Dowex 50) with water. The fractions containing the desired 1- (3-mercaptobutanoyl) -L-proline are pooled and lyophilized to give 0.6 g. The dicyclohexylamine salt is prepared by the method of Example 43, it melts at 183-184 ° C.

Example 45 *:

3-Acethylthio-2-methylpropanoic acid A mixture of 50 g of thioacetic acid and 40.7 g of methacrylic acid is heated in a water bath for 1 h and then kept at room temperature for 18 h. After confirming by NMR spectroscopy that the complete reaction of methacrylic acid has taken place, the reaction mixture is distilled under vacuum and the desired 3-acetylthio-2-methylpropanoic acid is separated in the boiling fraction at 128.5 -131 ° C / 2.6 mm Hg; the yield is 64 g.

Example 46 *:

3-acetylthio-2-phenylpropanoic acid By substituting 2-phenylacrylic acid for methacrylic acid in the process of Example 45, 3-acetyl-2-phenylpropanoic acid is obtained.

1- (3-acetylthio-2-phenylpropanoyl) tert-butyl ester Lpyroline

By substituting 3-acetylthio-2-phenylpropanoic acid for 3-acetylthio-2-methylpropanoic acid in the process of Example 22, the t- (3-acetylthio-2-phenyl-) t-butylester is obtained. propanoyl) -L-proline.

Example 47:

l- (3-mercapto-2-phenylpropanoyl) -Lproline By substituting the t-butyl ester of l- (3-acetylthio-2-phenylpro-panoyl) -L-proline for the t-butyl ester of l- (3-acetylthio-2 -methyl-propanoyl) -L-proline in the process of example 23 and by subjecting the product to an ammonolysis as in example 26, one obtains l- (3-acetylthio-2-phenylpropanoyl) -L-proline and 1- (3-mercapto-2-phenylpropanoyl) -L-proline.

Example 48 *:

Acid 1 - [3- (acetylthio) -DLpropanoyQpipecolic 6.5 g of pipecolic acid is suspended in 200 ml of dimethylacetamide. 8.3 g of 3-acetylthiopropanoyl chloride at 23 ° C are added dropwise to the suspension. A clear solution is formed and the temperature rises to 28 ° C. To this clear solution is added 10.1 g of N-methylmorpholine. A precipitate is immediately formed and the temperature rises to 34 ° C. The mixture is heated in a water bath for 1 h and then a clear solution is formed. During cooling, the precipitated solid is filtered to obtain 5.1 g of l- [3- (acetylthio) -DL-propanoyl] -pipecolic acid which melts at 190-200 ° C. The solvent is separated and triturated the viscous residue with isopropyl ether to obtain 7.8 g of product which melts at 98-101 ° C. Recrystallization from acetone-hexane gives a solid with a constant melting point which melts at 102-104 ° C; has an Rf value = 0.72 (silica gel, 7: 2 mixture of benzene: acetic acid).

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Example 49:

DLrl - {3-mercaptopropanoyl) pipecolic acid

12 ml of concentrated ammonium hydroxide are stirred under nitrogen at 10 ° C for about 15 minutes and then 6.6 g of 5 - 1- (acetylthio) -DL-propanoyl] pipecolic acid are added. -10 ° C. A clear solution is formed after 2-3 minutes. The ice bath is removed and the solution is stirred at room temperature under nitrogen for 45 min. The solution is strongly acidified with 20% HCl (cooling) and the precipitated oil is extracted with three times 150 ml of ethyl acetate. The ethyl acetate extracts are dried over magnesium sulfate and the solvent is removed to obtain 6.0 g of DL-1- (3-mercaptopropanoyl) pipecolic acid which has an Rf value = 0.77 (silica gel) , 7: 1 mixture of benzene: acetic acid).

Example 50:

Acid 1 - (3-mercaptopropanoyï) -Lpipécolic

By substituting L-pipecolic acid for DL-pipecolic acid in the process of Example 48 and then subjecting the product to the process of Example 49, we obtain l- [3- (acetylthio) - propanoyl] -L-pipecolic and 1- (3-mercaptopropanoyl) -L-pipecolic acid having an Rf value = 0.80 (silica gel, 7: 1 benzene mixture: acetic acid); value [x] 20 = —51.5 (c, 1.0 absolute ethanol).

Example 51 *:

Acid 1 - \ 3- (acetylthio) -2-methylpropanoyl \ -DLpipecolic

6.5 g (0.05 m) of pipecolic acid are suspended in 200 mg of dimethylacetamide, and 9.0 g (0.05 m) of 3-acetylthio-2-methylpropanoyl chloride are added dropwise . The temperature rises to 29 ° C and a clear solution is formed. 10.1 g of N-methylmorpholine are then added at once and the temperature rises to 34 ° C. The mixture is heated in a water bath for 1 h and then a clear solution is formed. It is left to stand at room temperature overnight and the precipitated solid is filtered off to obtain 6.1 g which melts at 203-204 ° C. The solvent is separated off and the viscous residue is triturated with water and 20% HCl. The yellow oil is extracted with three times 150 ml of ethyl acetate. The ethyl acetate extracts are dried over magnesium sulphate and separated to obtain 14 g of 1 - [3- (acetylthio) -2-methylpropanoyl] -DL-pipecolic acid in the form of a viscous oil. .

Example 52:

1- (3-Mercapto-2-methylpropanoyl) -DLpipecolic acid

Aqueous NH4OH (30 ml of water and 20 ml of concentrated NH4OH) is stirred under nitrogen at 10 ° C for 15 min. This is added to 13.0 g (0.05 m) of 1- [3- (acetylthio) -2-methylpropanoyl] -DL-pipecolic acid and the resulting solution is stirred for 10 min under nitrogen; then at room temperature for 50 min. It is then treated with water and 20% HCl and the yellow oil is extracted with three times 150 ml of ethyl acetate. The ethyl acetate extract is dried over magnesium sulfate and separated to obtain 11.1 g of 1- (3-mercapto-2-methylpropanoyl) -DL-pipecolic acid as an oil viscous. The Rf value = 0.62 (silica gel, 7: 2 mixture of benzene: acetic acid).

Example 53:

l- {3-mercapto-2-D-methylpropanoyl) -Lrproline 10.0 g of l- [3- (acetylthio) -2-D-methylpropanoyl] -L-proline are suspended under an argon blanket in 150 ml of water at 10 ° C. 5N sodium hydroxide is added to this mixture and the pH of the solution is kept at 13 for 1 h. After this time, when the absorption of sodium hydroxide has ceased, the solution is acidified to pH = 2.0 with concentrated sulfuric acid.

The aqueous solution is then extracted three times with methylene chloride (3 x 150 ml) and the combined methylene chloride fractions are concentrated until an oil is obtained. The concentrate is taken up in ethyl acetate, filtered and the filtrate is diluted with 30 ml of hexane. A new quantity of hexane is added after 1 h, then the mixture is cooled to 10 ° C. for 1 h.

The crystals are filtered and washed with twice 25 ml of hexane and dried to constant weight to obtain l- (3-mercapto-2-D-methylpropanoyl) -L-proline in the form of 6.26 g white crystals that melt at 100-102 ° C.

Example 54 *:

l- {3 - {[(ethylamino) carbonyl] thio} propanoyl} -Lproline 0.45 ml of ethyl isocyanate is added to a solution of 1 g of l- (3-mercaptopropanoyl) -L-proline in a mixture of 5 ml of sodium hydroxide N and 5 ml of pyridine. The solution is heated at 40 ° C for 4 h and concentrated in vacuo. The residue is distributed between 0.1N hydrochloric acid and ethyl acetate. The organic layer is washed with water, dried over magnesium sulfate and concentrated to dryness to obtain l- {3 - {[(ethyl-amino) carbonyl] thio} propanoyl} -L-proline. The dicyclohexylammonium salt is prepared by adding the dicyclohexylamine to a solution of the free acid in ethyl acetate; it melts at 150-152 ° C.

Example 55:

l- (3-mercaptopropanoy [) - Lrproline A solution of 75 mg (0.27 mmol) of 1- {3- [[(ethylamino) carbonyl] thio [propanoyl j -L-proline in 1 ml each is allowed to stand concentrated ammonium hydroxide and water at room temperature for 18 h under argon. The solution is diluted with a small amount of water and extracted with ether. The aqueous layer is acidified with cold concentrated hydrochloric acid and extracted with ethyl acetate. The combined extracts are dried and concentrated in vacuo to obtain a compound which is identical to the product of Example 18. Thin layer chromatography (silica gel; 7: 3 benzene mixture: acetic acid).

Rf = 0.4.

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Claims (5)

624,932 1. Process for the preparation of a compound of formula: r „ h2c (ch) m h — s— (ch) —ch co — n ch- not (I) -cor in which R is a hydroxyl group, NH2 or lower alkoxy; R 1 and R 4 are each a hydrogen atom, a lower alkyl, phenyl or lower phenylalkyl group; R3 is a hydrogen atom, a hydroxyl group or a lower alkyl group; m is 1,2 or 3; n is 0.1 or 2; as well as their basic salts, characterized in that a compound of formula is deprotected; 8 (ch) -ch — co — n n (ch) m -cor in which R8 is a protective acyl residue. 2. Method according to claim 1, characterized in that the product is of formula; hs- (ch_) -ch-t n -CO- cooh in which Rj is hydrogen or a lower alkyl group. 2 3 is a hydrogen atom, a hydroxyl or lower alkyl group R 1 and R 4 are each a hydrogen atom, a lower alkyl, phenyl or lower phenylalkyl group; R; laughing; m = 1 to 3; n is 0.1 or 2. s Asterisks indicate asymmetric carbon atoms. Each of the carbon atoms carrying a substituent Rls R3 and R4 is asymmetric when this substituent is other than hydrogen. In general, the compounds of formula I are preferred in which R is a hydroxyl or lower alkoxy group; Rj is a hydrogen atom or a lower alkyl group; R3 and R4 are each a hydrogen atom; m = 2, n = 0.1 or 2 and especially 1. Particularly preferred are the compounds of formula II: r. hs— (ch,) -2 n ch. co - n cgr 30 3. Method according to claim 1, characterized in that the product is of formula; hs- -ch. -ch- -CO- -not- -cooh in which R, is a lower alkyl group. 4. Method according to claim 1, characterized in that the product has the formula: ch., hs- -ch. -ch- -CO- cooh 5. Method according to claim 1, characterized in that the product is l- (3-mercapto-2-D-methylpropanoyl) -L-proline.