CA1138878A - Mercaptoacyl derivatives of keto substituted proline and pipecolic acid - Google Patents

Abstract

ABSTRACT

This invention is directed to compounds of the formula

Description

7~

MERCAPTOACYL DERIVATIVES OF KETO SUBSTITUTED
PROLINE AND PIPECOLIC ACID

This invention relates to keto derivatives of mercaptoacyl proline and pipecolic acid of formula I and salts thereof (I) o C \

l3 ~ (H21)p (IH2)q R4-S-(CH)m C - C - - N - - C*COOR
I H

R and R2 are independently selected from hydrogen and lower alkyl provided that R2 is lower alkyl only if Rl is al~o lower alkyl~
Rl and R3 are independently selected from hydrogen, lower alkyl, lower alkylthio, -(CH2) -SH, and halo substituted lower alkyl.
R4 is hydrogen, a hydrolyzably removable protecting group, a chemica-ly removable protecti:ng groupr or when Rl and R3 are other than -(CH2~n-SH
a sulfide of the formula /c \
(~2C)p (C~2)q l3 -S-(CH) -C- C - N ~ COOR
m I I

m is zero, one or two.
n i~s one, two or three p and q are each one or two provided that both are not two.
The asterisk in the above formula indicates a center of asymmetry in the ring. In the case oE
proline, i.e., p and q are both one, this center i5 in the L-configuration. In the case of pipecolic acid, i.e. r one of p and q is two, this center is in the D,L or L-configuration.
Asymmetric centers can also be present in the mercaptoacyl sidechain depending upon the deinition of Rl, R2 and R3. The products can accordingly exist in stereoisomeric forms or as racemic mixtures thereof. All of these are within the scope of the invention. The synthesis described below can utilize the racemate or one of the enantiomers as starting materials. When the racemic starting material is used in the synthesis procedure, the stereoisomers obtained in final product can be separated by conven-tional chromatographic or fractional crystallization methods. Preferably, if there is an asymmetric center in the mercaptoacyl sidechain, it is in the D-coniguration.

This invention in its broadest aspects relates to the mercaptoacyl derivatives of proline and pipecolic acid having formula I above and to salts thereof, to compositions containing such compounds and to the method for using such compounds as anti-hypertensive agents.
The term lower alkyI as used in defining the symbols ~, Rl, R2~ and R~ are straight or branched chain hydrocarbon radicals having up to seven carbons, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, iso-pentyl, etc. The preferred lower alkyl groups are up to ~our carbons with methyl and ethyl being most preerred. Similarly, the terms lower alkoxy and lower alkylthio reer to such lower alkyl groups 20 attached to an oxygen or sulfur.
The term halo substituted lower alkyl refers to such lower alkyl groups described above in which one or more hydrogens have been replaced by chloro, bromo or fluoro groups such as trifluoromethyl, pentafluoroethyl, 2,2,2-trichloroethyl, chloromethyl, bromomethyl, etc.
The term hydrolyzably removable protecting group employed in defining R4 refers to a group that can be removed by conventional hydrolysis or ammonolysis. Acyl groups of the formula ll R -C-7~

are suitable for this purpose wherein R can be lower alkyl of 1 to 7 carbons, lower alkyl substituted with one or more chloro, bromo or 1uoro groups, -(CH2)r-cycloalkyl wherein the term cycloalkyl refers to saturatad rings of 3 to 7 carbon atoms, preferably cyclohexyl, an aryl group such as ( 2)r ~ ~ a hetero group such as (CH2)r ~ , ~
or (CH2) r~J wkerein r is zero one two or three;

R6 is hydrogen, lower alkyl of 1 to 4 carbons, espe-cially methyl, lower alkoxy Qf 1 to 4 carbons, esp~cially methoxy, lower alkylthio of 1 to 4 carbons, especially methylthio, chloro, bromo, Eluoro, tri-fluoromethyl, or hydroxy; and X is oxygen or sulfur.
Preferred groups are the lower alkanoyl groupr~
having up to our carbons, especially acetyl/ and benzoyl.
The term chemically removable protecting group employed in defining R4 refers to groùps such as p-methoxy, p-methoxybenzylcarbonyl, trityl, t-butoxycarbonyl t etc. These groups can be removed after the completion of the acylation reaction by various means such as by treatment with trifluoro-acetic acid and anisole.
Preferred compounds of formula I are the L-proline containing derivative, i.e., p and q are both one, and R is hydrogen.

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~5-~ ith respect to the mercaptoacyl sidechain, preferred as final products are those compounds wherein R4 is hydrogen; m is zero or one; R3 is hydrogen; and Rl and R2 are both lower alkyl of 1 to 4 carbons~ especially both methyl, or R2 is hydrogen and Rl is hydrogen, lower alkyl of 1 to 4 carbons, especially methyl, trifluoromethyl, methyl-thio, or mercaptomethyl. Also preferred as both intermediates and final products are the above sidechains wherein ~4 is lower alkanoyl of 1 to 4 carbons, especially acetyl, or benzoyl.
Especially preferred as final products are the compounds of formula I having the mercaptoacyl side-chain wherein R4 is hydrogen; m is one; R3 and Rl are hydrogen; R2 is methyl or hydrogen; and when R2 is methyl the asyn~etric carbon atom to which R2 is attached i~ in the D-configuration.
The compounds of formula I are obtained by coupling a keto-substituted proline or pipecoli.~ acid o the formula ~II) O
Il C \

( 2l)p (1CH2)q HN ~-COOR
H
with an acid or its chemical equivalent of the formula ~3`~

~6 (III) l3 ll R4-S-(CH)-- C - COOH

wherein R4 is hydrogen, a hydrolyzably or chemically removable protecting group to yield the product of th~
formula (IV) ~ c ~
R13 Rl (H2C)p ~I 2 q R4-S-(CH~m- C - CO - N ~ ~-COOR

This reaction can be effected in the presence o a coupling agent such as dicyclohexylcarbodiimide or the like, or the acid can be activated by ormation of its mixed anhydride, symmetrical anhydride, acid halide, active ester or use of Woodward reagent EC, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline or the like~ For a review of the methods or acylation, see Methoden der Organishchen Chemie (Houben-Weyl), Vol. XV, part II, page l et seq. (1974). Preferably, the acid halide, especially the acid chloride, of formula III is reacted with the acid of formula ~T.
If the proline or pipecolic acid of formuIa II is reacted in the ester form the resulting ester prod-uct can be converted to the free acid, i.e., R is hydrogen, by _7_ HA216 conventional means. For example, if R is ethyl this es~er pro-tecting yroup can be removed by saponifi-cation.
The product of formula IV is preferably isolated and purified by crystallization, e.g., by forming the dicyclohexylamine salt and then converting the salt to the free acid form by treatment with an aqueou~ solution of an acid, such as potassium acid sulfate.
The product of formula IV bearing the acyl group R5-CO- can be converted to the products of formula I wherein R4 is hydrogen by conventional hydrolysis or by ammonolysis.
The products of formula I wherein Rl and R3 are other than -(CH2~-SH and R4 is o / C\
13 11 (H21)p (!H2)q -S- (CH)m-- C - CO ~ _ _ C* COOH
H

are obtained by directly oxidizing with iodine a product of formula I wherein R4 is hydrogen.
The esters of formula I wherein R is lower alkyl can be obtained from the carboxylic acid compounds, i.e., wherein R is hydrogen, by conventional est2rification procedures, e.y., by esterification with a diazoalkane such as diazomethane, a l-alkyl-3-p-tolyltriazene, such as 1-n-butyl-3-p-tolyltria-zene, or the like.

~3~ 78 ~A216 The compo-mds of Formula I can also be prepared by deprotecting, according to conventional methods, a keto-substituted proline or pipecolic acid produc-t of Formula I having the keto-function protected by the conventional protecting groups as for example, a ketal protecting group, e.g., a dialkoxy ketal, as for example, H C CH
(V~ 3O \ / O 3 C\

R3 Rl 2I p (IH2)q R4 S ( )m ~ C*~COOR

which can be deprotected by hydrolysis, as with an aqueous solution of hydrochloric acid at room temperature.
The compounds of Formula V can be prepared by starting with an N-carbobenzyloxy keto substituted proline or pipecolic acid of Formula II which is then treated with methanol in the presence of trimethyl orthoformate and concentrated sulfuric acid and the N-protecting group is then removed by hydrogenolysis in the presence of a palladium carbon catalyst to yield the dimethoxy intermediate of the formula O"~ O
(VI) / \
(H2 1 )p ( IH2)q HN - -C - COOR
H

~l~L31~

~9_ The intermediate of formula VI is then coupled with an acid or its chemical equivalent of formula III to yield the dimethoxy compounds of formula V.
Reference is also made to the following publica-tions for additional illustrative methodology forproducing starting materials and intermediates: U.S.
Patents 4,046,889, 4,105,776, 4,154,935 and 4,116,962;
Can. J. Biochem. & Physiol. 37, 583-587, (1959); JACS
79, p. 185-192, (1957); JACS 79, p. 192-197, (1957);
lQ Bull. Soc. Chem., 1965(8), p. 2253-2259; and Aus. J.
Chem. 20, p. 1493-1509, (1967).
The procedures illustrated therein can be utilized as general methods for the synthesis of compounds and separation of isomers which can be utilized in the invention described in this applicat:ion.
Additional illustrative details are found in the examples which serve as models or the preparation of other members of the group.
The compounds o this invention ~orm basic salts with a variety of inorganic or organic bases.
The salt forming ion derived from such bases can be metal ions, e.g., aluminum, alkali metal ions, such as sodium or potassium, alkaline earth metal ions such as calcium or magnesium, or an amine salt ion, of which a number are known for this purpose, for example aralkylamines like dibenzylamine, N,N-dibenzylethylenediamine, lower alkylamines like methylamine, t-butylamine, procaine, lower alkyl-piperidines like N-ethylpiperidine, cycloalkylamines, like cyclohexylamine or dicyclohexylamine, 1-~ 7~ HA216 adamantanamine, benzathine, or salts derived from amino acids like arginine, lysine or the like. The physiologically acceptable salts like the sodium or potassium salts can be used medicinally as described below and are preerred. rrhese and ather salts which are not necessarily physiologically acceptable are useful in isolating or puriying a product acceptable for the purposes described below, as illustrated with the dicyclohexylamine salt in the examples. The salts are produced by reacting the acid form of the compound with a equivalent of the base supplying the desired basic ion in a medium in which the salt precipitates or in aqueous medium and then lyophilizing. The free acid form can be obtained from the salt by conventional neutraliza~ion techniques, e.g., with potassium bisulfate, hydrochloric acid, etc.
The compound o ~ormula I wherein R4 is hydrogen, ll , or the disulfide type substituent, especially wherein R4 is hydrogen, are useful as hypotensive agents. They inhibit the conversion of the decapeptide angiotensin I to angiotensin II and, there~ore, are useul in relieving an~iotensin related hypertension. The action of the enzyme renin on angiotensi~ogen, a pseudoglobuli~ in blood plasma, produces angiotensin I. Angiotensin I is converted by angiotensin converting enzyme (ACE) to angiotensin II. The latter is an active pressor substance which has been implicated as the ~ HA216 causative agent in various forms of hypertensionin various mammalian species, e.g., rats and dogs.
The compounds of ~is invention intervene in the an-giotensinogen ~ (renin~ ~ angiotensin I -~ (ACE) ~
angiotensin II sequence by inhibiting angiotensin converting enzyme and reducing or eliminating the formation of the pressor substance angiotensin II.
Thus by the administration of a composition containing one, or a combination of compounds o formula I
angiotensin dependent hypertension in the species of mammal suffering thererom is alleviated. A
single dose, or preferably two to four divided daily doses, provided on a basis of about ~.1 to 100 mg.
per kilogram of body weight per day, preferably about 1 to 15 mg. per kilogram of body weight per day is appropriate to reduce blood pressure. The substanco is preerably administered orally, but parenteral routes such as the subcutaneous, intramuscular, intravenous or intraperitoneal routes can also be employed.
The compounds o this invention can also be formulated in combination with a diuretic for the treatment of hypertension. A combination product comprising a compound of this invention and a diuretic can be administered in an effective amount which comprises (for a 70 kg. mammal) a total daily dosage of about 30 to 600 mg., preferably about 30 to 300 mg., of a compound of this invention, and about 15 to 300 mg., preferably about 15 to 200 mg.
of the diuretic, to a mammalian species in need thereof. Exemplary of the diuretics contemplated for use in combination with a compound of this invention are the thiazide diuretics, e.g., chlor-thiazide,hydrochlorothiazide, flumethiazide, hydro-glumethiazide,benzdroflumethia~ide, methchlothiazide,trichlormethiazide, polythiazide or benzthiazide, as well as ethacrynic acid, ticrynafen, chlorthalidone, furodemide, musolimine, bumetanide, triamterene, amiloride and spironolactone, and salts of such compounds.
The compounds of formula I can be formulated for use in th~ reduction of blood pressure in compositions such as tablets, capsules or elixirs for oral administra~ion or in sterile solutions or suspensions for parenteral administration. About 10 to 500 mg. of a compound or mixture of compounds of ormula I is compounded with a physiologically acceptble vehicle, carrier, excipient, binder, preser~ative, stabilizer, ~lavor, etc~, in a unit dosage form as called for by accepted pharmaceutical practice. The amount of active substance in these compositions or preparations is such that a suitable dosage in the range indicated is obtained.
Illustrative process details are set forth in the following examples for the various reactions.
These examples are preferred embodiments and also ser~e as models for the preparation of other compounds of this invention. The temperatures are given in degrees on the centigrade scale.

:

_13_ HA216 Example 1 1-[3-(Acetylthio)-l-oxopropyl]-4-oxo-L-proline a) N-Carbobenæyloxy-4-hydroxy-L-proline 26.5 g. (0.02 mole) of 4-hydroxy-L-proline S and 32.8 ml. (0.23 mole~ of benzyl chloroformate are reacted in 200 ml. of water and 100 ml. of acetone in th~ presence of 20 g. (0.02 mole) of potassium bicarbonate and 69.2 g. (0.50 mole) of potassium carbonate and worked up with 90 ml. of concentrated hydrochloric acid as described in Can.J. Biochem. &
Physiol. 37, 584 (1959) to obtain N-carbobenæyl-oxy-4-hydroxy-L-proline. This produc~ is reac~ed with cyclohexylamine to form the cyclohexylamine salt yield 69 g., m.p. 193-195. The salt (34 g.) is neutralized with N-hydrochloric acid to obtain 27 g. of free acid as a colorless glass ~]D ~70 , (c, 1~ in chloroform).
b) ~!-carbobenzylo ~ oline 21.5 g. (0.81 mole) of N-carbobenzyloxy-4-~0 hydroxy-~-proline is oxidized in 1.2 li-ters o acetone with 83 ml. of 8N chromic acid in sulfuric acid as described in J.A.C.S.79, 189 (1957). In order to facilitate the subsequent filtration of chromium salts, 30 g. of Celite (diatomaceous earth) is added to the acetone solution before introduction of the oxidizing agent. An air stirrer is employed. The reaction mixture is filtered and the acetone filtrate is concentrated to approxima~ely 300 ml. before diluting with 1 liter of chloroform.
The solution is washed with 300 ml. of saturated ~3~ A216 -lLL-sodium chloride (four times), dried (MgSO4), filtered and the solvent evaporated to give N-carbobenzyloxy-4-keto-L-proline (22.8 g.) which i~ crystalli2ed from ether (50 mL.)-hexane (150 ml.) to obtain 17.2 g. (81%) of product, m~p.
99-101l [~]D6 ~17 (c,1~ in chloroform).
c) 4-~eto-1-proline, hydrobromide To 4.0 g. (0.015 mole) of N-carbobenzyloxy-4-keto-L-proline are added 20 ml. of hydrogen bromide in acetic acid (30-32~. The mixture is frequently swirled over a period of eight minutes. At the end of this period (effervescence has stopped), the yellow-orange solution is layered over with 250 ml. of ether, triturating the gummy product. The ether is discarded and the resulting tacky solid is triturated with fresh ether and finally with 50 ml. of acetoni.
trile to give 4-keto-L-proline, hydrobromide as a crystalline solid weighing 2.7 g. (85~), m.p.
153-155 ~dec.,), [a~D ~49 (c, 1% in water).
d) 1-[3-(Acetylthio)-l-oxoprop~1]-4-oxo-L-proline A stirred solution of 4.1 g. (0.0195 mole) of 4-keto-L~proline, hydrobromide in 50 ml. of water is cooled to 5 and treated portionwise with solid sodium carbonate (foaming is controlled by adding a few drops of ether) to pH 8.0 (approx. 2 g. required).
Then while continuing stirring and cooling, a solution of 3.5 g. (0.012 mole) of 3-acetylthio-propionyl chloride in 5 ml. of ethyl acetate is added portionwise by means of a pipette while maintaining the pH at 7.0 - 8.0 by dropwise addition H~216 of 25% (w/v) sodium carbonate solution (about 10 ml.).
~fter about 10 minutes the pH stabilizes at 8.0 -~.4. After continued stirring and cooling for a to-tal of 1 hour, the solution is washed with ethyl ace~ate (2 x 50 ml.), layered over with 50 ml. of ethyl acetate, stirred, cooled, acidified carefully with concentrated hydrochloric acid to pH 2.0, sa-turated with so~ium chloride, and the layers are separated.
The aqueous phase is extracted with additional ethyl acetate (3 x 50 ml.)~ the combined organic layers dried (MgSO4) and the solvent evaporated, finally at 0.2 mm. to give 4.8 g. of a yellow-orange glass-like residue. This residue is dissolved in 35 ml. of ethyl acetate and treated with a solution of 3.5 gO
of dicyclohexylamine in 5 ml. of ethyl acetate. On seeding and rubbing, crystalline l-[3-(acetylthio-1-oxopropyl)]-4-oxo-~-proline dicyclohexylamine salt separates, weight after cooling overnight, 2.7 g.
(nearly coLorless), m.p. 191-193 (dec.), [a]26 -24 (c, 1% in CHC13).
This dicyclohexylamine salt is converted to the free acid by suspending it in ethyl acetate and treati~g with 45 ml. of 10% potassium bisulfate and stirring until two layers are obtained. After separa-ting, the aqueous phase is extracted with ethyl acetate(4 x 75 ml.), the organic layers are co~bined, dried (~gSO4) and the solvent is evaporated to give 3.7 g.
of light yellow glass-like material.
Anal. Calc' do for CloHl3No5s:

~16-C, 46.32; H, 5.05; N, 5.40; S, 12.37;
Found: C, 47.05; H, 5.50; N, 5.18; S, 12.07.
Example 2 1 (3-Mercapto-l-oxoDropvl)-4-o~o-L-proline Argon is passed through a cold solution of 9 ml. o concentrated ammonia hydroxide in 2~ ml.
of water for 30 minutes. This material is then added while cooiing and under a blanket of argon to 3.65 g. (0.014 mole~ o l-[3-(acetylthio)-l-oxopropyl]-4-oxo-L-proline. Approximately 30 minutes are required to dissolve the proline starting with the aid of a magnetic stirrer.
Stirring under argon is continued a~ room temperature for an additional two hours after which the solution is extracted with 30 ml. of ethyl acetate (this and subsequent oparations are carried out as much as possible under an argon atmosphexe). The aqueous layer is cooled, stirred, layered over with 30 ml.
of ethyl acetate, and acidified portionwise with l:l HCl. Sodium chloride is added, the layers are separated, and the aqueous phase i5 axtracted with additional ethyl acetate (3 x 30 ml.). A brown gummy raction remains insoluble in either phase.
After drying over MgS04 the combined ethyl acetate layers are evaporated to give a mostly solid residue which becomes an amorphous solid when triturated with ether and theeVaporation repeated to yield 1.4 g. of pale yellow material.
1.3 g. of this material is rubbed under 50 ml. oP ether, cooled under argon for one hour, , ,;' .

. .

~38~3~

filtered, washed wlth ether, and dried ln vacuo to yield 1.O g. of 1-(3-mercapto-1-oxopropyl)-4-oxo-~p~line, ~f 0.67 (me~nol on silica gel. visu~lized Ln icdine vapor).
Anal. Calc d. for 8 11 4 2 - 5 C, 42.46; H, 5.35; N, 6.19; S, 13.71 Found: C, 42.66; H, 5.3~; N, 6.30; S, 13.30.
Example 3 ~S)-1-~3-Acetylthio)-2-methyl-1-oxopropyl?-4-oxo-L- roline _P
Following the procedure o Example 1 but substituting D-3-acetylthio-2-methylpropionyl chloride for the 3-acetylthioPrpiOnyl chloride, one obtains (S)-1-[(3-acetylthio)-2-methyl-1-oxo-propyl]-4-oxo-L-proline.
Example 4 (S)~ 3-Mercapto-2-methyl-1-oxopropyl) 4-oxo-L-proline The product from Example 3 is treated with ammonia hydroxide according to the procedure of Example 2 to yield (S)~ 3~ ercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline.
Example 5 1-~(3-Acetylthio)-2-trifluoromethyl-l-oxopropyl]-4 oxo-L-proline a) D L-3-(Acet lthio)-2-trifluoromethylpropionic acid Y
a-Trifluoromethyl acrylic acid (10 g., 0.071 mole) [prepared according to the procedure set forth in J. Chem. Soc., 1954, p. 371~ is cooled in a salt-ice-water bath, stirred and treated portion-wise with 5.7 ml.(0.075 mole) of 97~ thiolacetic ~31~

acid. After the addition, the yellow liquid is stirred in the cold for one hour, allowed to warm to room temperature, and distilled to yield 14 g.
(91~) of D,L-3-(acetylthio)-2-tri~luoromethyl-propionic acid as a light yellow oil, b.p.
149-153~13mm. The material solidifies on storing in the cold.
b) D,L-3-(Acetylthio)-2-trl1uorome-thylpropionyl chloride The D,L-3-(acetylthlo)-2-trifluoromethyl-propionyl acid (7 g., 0.032 mole) is treated with 18 ml. (0.25) of redistilled thionyl chloride and the mixture is refluxed for three hours. After remov~ng the excess thionyl chloride on a rotary lS evaporator, the residue is distilled to give 6.8 g.
of D,L-3-(acetylthio)-2-trifluoromethylpropionyl chloride as a pale yellow oil; b.p. 80-~2/16 mm.
c) 1~[(3-Acetylthlo)-2-tri1uoromethyl-1-oxoprop ~ -4-oxo-L-~roline ~0 The D,L-3-(acetylthio)-2-trifluoromethyl-propionyl chloride is reacted with 4-keko-L-proline, hydrobromide according to the procedure of Example 1 (d) to yield 1-[(3-acetylthio)~2-trifluoro-methyl-l-oxopropyl]-4-oxo l-proline. This mixture of diastereoisomers can then be separated by con~entional techniques.
Example 6 1-(3-Mercapto-2-triflu romethyl-1-oxopropyl)-4-oxo-L-proline The product from Example S (in the form of the diastereoisomer mixture or as the separated , , .

isomers) is hydrolvzed with concentrated ammonia according to the procedure of Example 2 to yield 1-(3-mercapto-2-trifluoromethyl-1-oxopropyl)-4-oxo-L-proline.
Example 7 (S)-1-(3-Mercapto-2-mercaptomethyl-1-oxopropyl)-4-oxo-L-proline a) (S)-1-[3-(Acetylthio)-2-(acetylthiomethyl)-1-_ oxopropyl~-4 oxo-L-proline Following the procedure of Example 1 but sub-stituting D-3-acetylthiomethyl-3-acetylthiopropionyl chloride for the 3-acetylthiopropionyl chloride in part (d), one obtains (S)-l- L3- (acetylthio)-2-(acetylthiomethyl)-1-oxopropyl] 4-oxo-L-proline.
b) (S)-1-(3-Mercapto-2-mercaptomethyl-1-oxo-propyl? -4 -oxo-L-proline The product from part (a) is hdyrolyzed wi~h concentrated ammonia according to the procedure of Example 2 to yield (S)-1-(3-mercapto-2-mercapto-methyl-l-oxopropyl)-4-oxo-L-proline .
Example 8 1-(3-Mercapto-2-methylthio-1-oxopropyl)-4-oxo-L-proline a) 3-(Acetylthio)-2-(methylthio)propionic acid -12.5 g. (0.094 mole) of methyl-2-(methylthio)-acrylate ~prepared from methyl 2-chloroacrylate according to the procedure of Gundesmann et al., Chemische Berichte 94, 3254 (1916)] is stirred with lN aqueous sodium hydroxide (94 ml.) with ice cooling. The mixture is allowed to warm to ambient temperature, then stirred for five hours. The ., .

',~
~`

' "'' 1~3~878 HA216 resulting solution is washed wi-th ether, then acidi-fied to pH 2 with concentrated hydrochloric acid.
The solid precipitate is extracted into methylene chloride, and the solution is washed with saturated sodium chloride and the solvent evaporated. The solid residue, 2-(methylthio)acrylic acid; m.p.
70-75, is used immediately in the following reaction.
Equimolar amounts of 2-(methylthio)acrylic acid and thiolacetic acid are mixed ~mder argon and - stirred at 80 for.several hours to yield 3~(acetyl-thio)-2-(methylthio)propionic acid.
b) 3-(Acetylthio)-2-(methylthio)propionlc acid chloride .
The 3-(acetylthio)-2-(methylthio)propionic acid is refluxed in thionyl chloride for two hours. The reaction mix~ure is distilled to remove excess thionyl chloride and the product is `
distilled ln vacuo to yield 3-(acetyl-thio)-2-(methyl-thio)propionic acid chloride.
c) l-~3-(Acetylthio)-2-methylthio-1-oxopropyl~-4-The 3-(acetylthio)-2-(methylthio)propionic acid chloride is reacted with 4-keto-L-proline, hydrobromide according to the procedure of Example 1 (d) to yield 1-~3-(acetylthio)-2-methyl-thio-l-oxopropyl]-4-oxo-L-proline.
d) 1-(3-Mercapto-2-methylthio-1-oxopropyl)-4-_ oxo-L-proline The product from part (c) is hydrolyzed with ;:
' ;

i 7~

concentrated ammonia according to the procedure of Example 2 to yield 1-(3-mercapto-~-methylthio-1-oxoprop~ 4-oxo-L-proline.
Example 9 1-(4-Mercapto-l-oxobutyl)-4-oxo-L-proline -a) l-[4-tAcetylthio)-l-oxobutyl.]-4-oxo-L-proline Following the procedure of Example 1 but substituting 4-acetylthiobutyroyl chloride for the 3-acetylthiopropionyl chloride in part (d), one obtains 1-~4-(acetylthio)-1-oxobutyl]-4-oxo-L-proline.
b) l-(4-Mercapto l-oxobutyl)-4-oxo-L-proline The product form part (a) is hydrolyzed with concentrated ammonia according to the procedure of Example 2 to yield 1-(4-mercapto-1-oxobutyl)-4-oxo-L-proline.
E ~
1-(2-Mercapto-l-oxoeth~ 4-oxo-L-proline a) l-[2-(Acetylthio)-l~oxoethyl]-4-oxo-L-proline Following the procedure of Example 1 but substituting acetylthioacetyl chloride for the 3-acetylthiopropionyl chloride in part (d), one obtains 1~[2-(acetylthio)-1-oxoethyl]-4-oxo-L-proline.
:. 25 b) 1-(2-Mercapto-l-oxoethyl)-4-oxo-L-proline :- The product from part (a) is hydrolyzed with concentrated ammonia according to the procedure of Example 2 to yield 1-(2-mercapto-1-oxoethyl)-4-: oxo-L-proline.

.~
., .

,-. ~

8~
H~216 - Example ll 1-(3-Mercapto-2,2-dimethyl-l-oxopropyl)-4-oxo-L-proline a) l-[3-(Acethylthio)-2,2-dimethyl-l-oxopropyl]-4-oxo~L-proline Following the procedure of Example l but substituting 3-acetylthio-2,2-dimethylpropionyl chloride for the 3-acetylthiopropionyl chloride in part (d), one obtains l-[3-(acetylthio)-2,2-dimethyl-l-oxopropyl~-4-oxo-L-proline.
b) 1-(3-Mercapto-.2,2-dimethyl-l-oxopropyl)-4-oxo-L-proline The product from part (a) is hydrolyzed with concentrated ammonia according to the procedùre ~5 of Example 2 to yield 1-(3-mercapto-2,2-dimethyl-1-oxopropyl)-4-oxo-L-proline.
Example 12 (S)-l (3-Mercapto-2-ethyl-l-oxopropy proline a) _(S)~ 3-(Acetylt_ o)-2-eth~-l-oxoprop~
oxo-L-proline Following the procedure of Example 1 but substituting D-3-acetylthio-2-ethylpropionyl chloride .: ~or the D-3-acetylthio-2-methylpropionyl chloride in part (d), one obtains (S)~ 3-(acetylthio)-2-ethyl-l-oxopropyl]-4-oxo-L-proline.
-~ b) (S)-1-(3-Mercapto-2-ethyl-l-oxopropyl)-4-L-pro l lne . The product from part (a) is hydrolyzed with ~ 30 concentrated ammonia according to the procedure of ,:,.

~3~7~ ~A216 Example 2 to yield (S)-1-(3-mercapto-2-ethyl-1-oxopropyl)- -oxo-L~proline.
. Example 13 1-(3-Mercapto-l-oxopropyl)-4-oxo-L-Dipecolic ac1d S a) 1-[3-(Acetylthio)-l-oxopropyl]-4-oxo~L-pipecolic acid Following the procedure of Example 1 but substituting 4-keto-L-pipecolic acid for the 4~
keto-L-proline in part (d), one obtains 1-13-(acetyl-thio)-1-oxopropyl~~4-oxo-L-pipecolic acid.
b) 1-(3-Mercapto-l-oxopropyl)-4-oxo-L-pipecolic _cid The product from part (a) is hydrolyzed with concentrated ammonia to yield l-(3-mercapto-1-oxopropyl)-4-oxo-L-pipecolic acid.
lS Example 14 (S)-1-(3-Mercapto~2-methyl-1-oxopropyl)-S-oxo-L
pipecolic acid a? (S)-1-~3-(Acetylthio)-2-methyl-1-o~opropyl]-S-oxo-L-pipecolic acid Following the procedure of Example 1 but substituting 5-keto-L-pipecolic acid for the 4-keto-L-proline in part (d) and D-3-acetylthio-2-methylpropionyl chloride for the acetylthiopropionyl chloride in part (d), one obtains (S)-1-[3-(acetyl-thio-2-methyl-1-oxopropyl]-5-keto-L-pipecolic acid.
b) (S)-1-(3-Mercapto-2-methyl-1-oxopropyl)-5-keto-L-pipecolic acid ; The product from part (a) is hydrolyzad wi~h concentrated ammonia according to the procedure of ; 30 Example 2 to yield (S)-1-(3-mercapto-2-methyl-1-

-2~

oxopropyl)-5-keto-L-pipecolic acid.
Example 15 1-(3-Mercapto-2-trifluoromethyl-1-oxopropyl)-4-oxo-L-proline a) 3-[[(4-Meth xy)phenylmethyl]thio]-2-trifluoro-methylpropionyl chloride A neat mixture of l-tri1uoromethylacrylic acid (3.9 g.) and 4-methoxybenzylthiol (4.3 g.) is stirred at 100-110 for one hour. The mixture is allowed to ccol to room temperature and the solid is recrystallized from cyclohexane to yield 3-[[(4-methoxy)phenylmethyl]thio]-2-trifluoromethylpro-pionic acid; m.p. 72-74.
Treatment of this acid with thionyl chloride yields 3-[[(4-methoxy)phenylmethyl]thio]-2-trifluoro-methylpropionyl chloride.
b? 1-[3-~[t4-Methoxy)phenylmethyl]thio]-2-trifluc)ro-methyl-l-oxopro~l]-4-oxo-L-proline 1'he 3- E ~ (4-methoxy)phenylmethyl]thio]-2-trifluoromethylpropionyl chloride from part ~a) is ; reacted with 4-keto-L-proline to yield 1-[3-[[(4-methoxy)phenylmethyl]thio]-2-trifluoromethyl-1-oxopropyl¦-4-oxo-L-proline.
c) 1-(3-Mercapto-2-trifluoromethyl-1-oxopropyl)-4-`~ 25 oxo-L-proline The product from part (b) is mixed with trifluoroacetic acid and anisole under nitrogen.
The solvents are removed under vacuum to yield as a residue 1-(3-mercapto-2-trifluoromethyl-1 oxopro-yl)-4-oxo-L-proline.

~:, ~3~

-~5-Example 16 (S)-1-(3-Mercapto-3-methyl-l-oxopropyl)-4-oxo-, L-proline a) (S)-1-[3-(~cetylthio)-3-methyl-1-oxopropyl]-4-oxo-L-proline Following the prodecure of Example l but substituting D-3-acetyl-thio-3-methylpropionyl chloride for the 3-acetylthiopropionyl chloride in part (d), one obtains (S)-l-[3-~acetylthio)-3-methyl-l-oxopropyl]-4-oxo-L-proline.
b) ~S)-l-_t3-Mercapto-3-methyl-l-oxopropyl)-4-oxo-L-proline The product from part (a) is hydrolyæed with concentrated ammonia to yield (S)-l-~3-mercapto-

3-methyl-1-oxopropyl)-4-oxo-L-proline.
Examples 17 - 25 Following the procedure of Example l but substituting ~or the 3-acetylthiopropionyl chloride the acid chloride listed below in Col. I one obtains the acylmercapto product listed below in Col. II.

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-~8-Example ? 6 (S)-1-(3-Mercapto-2-methyl-1-oxopropyl~-4-oxo-L-roline l-adamantanamine salt P
The product of Example 4 can also be prepared 5 according to the followinc; pro~edure.
a) N-Carbobenzyloxy-4,4-dLmetho~y-L-proline, meth~l ester A stirred solution of 7.8 g. (0.03 mole) of N-carbobenzyloxy-4-keto-L~proline rom Example 1 in 60 ml. of methanol is treated with 96 ml. of tri-methyl orthoformate, followed by 0.6 ml. ofconcentrated sulfuric acid and allowed to stand overnight at room temperature.
The pale yellow solution is stirred, treated with 1.5 g. of potassium carbonate, followed by 30 ml. of water and the bulk of the solvent is removed on a rotary evaporator to give a syrupy residue which is shaken with 30 ml. of water and 30 ml. of chloro-form. Ater separating the layers the aqueous phase is extracted with additional chloroform (3 x 30 ml.) and the combined organic layers are washed with 45 ml.
of saturated sodium chloride solution and dried (MgSO4). Evaporation of the solvent yields 8.4 g.
(88~) of N-carbobenzyloxy-4,4-dimethoxy-L-proline, methyl ester.
b) N-Carbobenzyloxy-4,4-dimethoxy-L-proline The ester (8.4 g., 0.026 mole) from part(a) is dissolved in 80 ml. of methanol, treated dropwise at -1 to 4 with 18 ml. (0.036 mole) of 2N sodium hydroxide kept at 0 for one hour, and at room temperature overnight. After removing about one half of the solvent on a rotary evaporator, the solution is diluted with 150 ml. of water, washed with 100 ml.
of ether (wash discarded), acidified while cooling with 63 ml. of 1:1 hydrochloric acid to pH 2, and sxtracted with ethyl aceta-te (4 x 750 ml.). The combined e~tracts are washed with 50 ml. of saturated sodium chloride solution, dried (MgSO4~, and the solvent evaporated to give 8 0 g. of a pale yellow viscous oil. The oil is dissolved in 35 ml. ethanol, treated with 3.0 ~. of cyclohexylamine in 10 ml. of ethanol and diluted to 500 ml. with ether. On seeding and rubbing~ the crystalline N carbobenzyloxy-4,4-; dimethoxy-L-proline cyclohexylamine salt separatedi weight after cooling overnigh~, 7.0 g., m.p. 157-159 (s, 151) [~26 _34 (c, 1~ in EtOH). This material is recrystallized from 100 ml. of acetonitrile to give the salt as a colorless solid, m.p. 158-160 (s, 154) [a]D ~33 (c, 1~ in EtOH).
The ~-carbobenzyloxy-4,4-dimethoxy L-proline ` cyclohexylamine salt is suspended in 40 ml. of ethyl acetate, stirred and treated with 25 ml. of lN
hydrochloric acid. When two clear layers are obtained they are separated, the aqueous phase is extracted with additional ethyl acetate (3 x 40 ml.), the combined organic layers are dried (MgSO4~, and the solvent evaporated, finally at 0.2 mm and 40 to yield 7.2 g. (70~) of N-carbobenzyloxy-4,4-dimethoxy-L-proline as a pale yellow viscous syrup.
c) 4,4-Dimethoxy-L-proline A solution of N-carbobenzyloxy-4,4-dimethoxy-L-proline (72 g., 0.022 mole) in 210 ml. of methanol-wa~er (2:1) is treated with 2.3 g. oE 5~ palladium-carbon and shaken on a Parr hydrogenator for 6 hours.
The catalys~ is filtered off under nitrogen, washed with methanol, and the combined filtrates are evaporated, finally at 0.1 - 0.2 mm.~ to give a partly crystalline residue. This residue is taken up in 2Q0 ml. of methanol and the evaporation repeated.
When the solid is rubbed under ether (evaporation again repeated) there is obtained 3.6 g. (95%) of nearly 10 colorless 4,4-dimethoxy-L-proline, m.p. 192-194 ~dec.); [a]26 -47 (c, 1~ in MeOH).
A sample crystallized from methanol-ether is colorless and melts at 197-198 (dec.), la]26 _49o ~c, 1% in MeOH).
15 d) tS)~ 3-(~cetylthio)-2-methyl-1-oxoprop~?-4,4~
dimethoxy-L-proline A stlrred solution o 3.3 g. (0.019 mole) of

4,4-dimethoxy-L-proline in 50 ml. of water is cooled to 5 and brought to pH 8.5 by the addition of 25%
- 20 sodium carbonate solution (w/v). Then while continuing stirring and cooling, a solution of 3.8 g. (0.021 mole) of D-3-acetylthio-2-methylpropanoyl chloride in 5 ml.
of ether is added portionwise while maintaining the pH at 7.5 - 8.5 by dropwise addition of 25~ sodium carbonate solution. When the pH has stabilized at 8.2 - 8.4 (after about 15 minutes), stirring and cool-ing is continued for a total of one hour. The solution is then washed with 50 ml. of ethyl acetate (wash discarded),layered over with 50 ml. of ethyl acetate, cooled, stirred, acidified carefully with 1:1 hydro-~31-chloric acid to pH 2.0, saturated with sodium chloride, and the layers separated. The aqueous phase is extracted with additional ethyl acetate (3 x 50 ml.), the combined organic layers are dried (MgSO~), and the solvent evaporated, finally at 0.2 mm, to give 6.7 g. of syrupy product. This syrup is treated in 70 ml. of ethyl acetate with 3.9 g. of dicyclo-hexylamine to give 6.5 g. of colorless (S)-l-[3-(acetylthio)-2-methyl-1- oxopropyl]-4,4-dimethoxy-L-proline dicyclohexylamine salt in two crops (3.1 g. and 3.4 g.), m.p. 158-160 (s, 145).
26 71 (c, 1% i~ EtOH).
Following recrystallization from 20 ml. of hot ethyl acetate-G0 ml. of hexane, the colorless solid salt weighs 6.0 g., m.p. 158-166 (s, 155), ]D -69 (cl 1% in EtOH).
The dicyclohexylamine salt is converted to the free acid by suspending 5.0 g. in 50 ml. of ethyl acetate, cooling and treating with 60 ml. of }0 potassium bisulfate solution to give 2 clear layers.
Ater separating, the aqueous phase is extracted with ethyl acetate (3 x 50 ml.), the combined organic layers are dried (MgSO4), and the solvent evaporated, finally at 0.1 - 0.2 mm. and 45 to give 4.1 g.
(69%) of (S)-1-[3-(acetylthio~-2-methyl-1-oxopropyl]-4,4-dimethoxy-L-proline as a viscous, almost glass-like material [a]D -112 (c, 1~ in EtOH).
e~ (S)-1-(3-Mercapto 2-methyl-1-oxopropyl)-4,4-dimethoxy-L-proline Argon is passed through a cold solution of 8.5 ml. of concentrated ammonium hydroxide in 20 ml. of water for 0~ 5 hour. The latter is then added while cooling and under a blanket of argon to 4.1 g.
(0.013 mole) of (S)-1-[3-(acetylthio~-2-methyl-1-oxopropyl]-4,4-dimethoxy-L-proline and the mixture is swirled in an icebath until a pale yellow solution is obtained (about 15 minutes). Stirriny under argon is continued at room temperature for an additional 2 hours, then the solution is extracted with 30 ml.
of ethyl acetate (this and subsequent operations are lQ carried out as much as possible under an argon atmosphere). The aqueous layer is cooled, stirred, layered over with 30 ml. of ethyl acetate, and acidiied portionwise with approximately 16 ml. of 1:1 hydrochloric acid. The layers are separated, the aqueous phase is extracted with additional e-thyl - acetate (3 x 30 ml.), the combined ethyl acetate layers are dried (MgSO4), and ~he solvent evaporated to give 3.5 g. (100%) o (S~ (3-mercapto-2-methyl-1-oxopropyl)-4,4-dimethoxy ~-proline as a colorless, viscous ~0 syrup, [a]25 -72 (c, 1~ in EtOH).
The latter ~3.4 g.) is triturated with 20 ml.
of ethyl acetate, rubbed, diluted with 30 ml. of hexane, and cooled to give a colorless solid, weight 2.6 g., m.p. 108-110 , [a]D -77 (c, 1~ in EtOH).
:.

~3~

f) (S)~ 3-Mercapto-2-me-thyl-1-oxopropyl)-4-oxo-L-Droline, l-adamantanamine salt The (S)-1-(3 mercapto-2-methyl-1-oxopropyl)-4,4-dimethoxy-L-proline (0.4 g., 0.0014 mole) is added to 8 ml. of stirred N HCl through which argon had previously been passed for ten minutes. After -a solution is obtained, the flask is stoppered under argon and kept overnight at room temperature.
The following steps are also carried out under an atmosphere of argon to the extent possible. To the stirred solution there is added 20 ml. o methylene chloride and after saturating with sodium chloride the layers are separated. The aqueous phase is extracted with additional methyl~ne chloride ~3 x 15 ml.), the organic layers are combined, dried (MgSO4), and the solvents evaporated to give a oamy residue. Following trituration with ether (evaporation repeated), 0.26 g.
of (S)-1-(3-mercapto-2-methyl-1-oxopropyl)~4-oxo-L-proline are obtained as an amorphous solid thygroscopic).
0.245 g. of this product is dissolved in 7 ml.
of acetonitrile and treated with 0.17 g. of l-adamantan-amine to precipitate the salt as a voluminous solid.
After cooling overnight, the colorless material is filtered, washed with cold acetonitrile and ether, and dried in vacuo to yield 0.36 ~. of (S)-1-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline, l-adamantanamine salt (1:1); m.p. 188-190 (dec.); s. 184; ~a]D -13 (c, 1~ in methanol).
Anal. Calc'd. for CgH13NO4S C10 17 C, 58.g6; H, 8.02; N, 7.24; S, 8.29 Found: C, 58.60; H, 8.37; N, 7.16; S, 8.29.

-3~-Example 27 1,1l-[Dithiobis(l-oxo-3,1-propanedivl)]bis[4-oxo-L-.
proline]
The product from Example 2 is dissolved in water and the pH adjusted to 6.5 by the addition of lN
sodium hydroxlde. To this stirred solution is added dropwise a 0.5 M iodine solu-tion in 95~ ethanol (6.34 g. iodine/50 ml. solution) while maintaining the pH at 5.5 to 6.5 with lN sodium hydroxide. Excess iodine is removed with dilute sodium thiosulfate and the solution is concentrated, cooled and acidified with l l hydrochloric acid. Solvent is added and the la~ers are separated. The organic layer is dried MgSO4) and the solvent evaporated to yield as a resldue 1,1'-Idithiobis(l-oxo-3,1-propanediylt]bis[4-oxo-L-proline].
Example 28 1~I3-(Acet~lthio)-l-oxopxopyl]-4-oxo-L-proline, methyl ester A solution of the product of Example 1 in ether is treatQd with a slight excess of diazo~ethane.
After standing at room temperature for two hours, the solvent is evaporated to give 1-[3-(acetylthio)-1-oxopropyl]-4-oxo-L-proline, methyl ester.
Example 29 1 (3-Mercapto-l-oxopropyl)-4-oxo-L-proline, methyl ester The product from Example 28 is hydrolyzed with concentrated ammonia according to the procedure of Example 2 to yield l-(3-mercapto-1-oxopropyl)-4-oxo--3~~

L-proline, methyl ester.
Example 30 1-(3-.~lercapto-1-oxopro~Yl)-4-oxo-L-proline, sodium s_ A solution of 1.0 g. of the product of Example 2 is dissolved in 10 ml. of water and treated with one equivalent of so~ium bicarbonate.
The solution is freeze-dxied to give 1-(3-mercapto-1-oxopropyl)-4-oxo-L-proliIle, sodium salt.
In a similar manner, by employing potassium bicarbonate the corresponding potassium salt is ob-tained.
Exam~le 31 (S)-1-(3-l~ercapto-2-methyl-1-oxopropyl)-4-oxo-L-~ . _ .
proline, sodium salt A solution of 1.0 g. of the product oE
Example 4 is dissolved in 10 ml. o water and treat:ed with one equivalent o sodium bicarbonate. The solution is freeze-dried to give 1-(3-mercap~o-2-methyl-1 oxopropyl)-4-oxo-L-proline, sodium salt.
In a similar manner, by employing potassium bicarbonate the corresponding potassium salt is obtained.
Example_32 1000 tablets each containing the following inqredients:
1-~3-mercapto-1-oxopropyl)-4-oxo-L-proline 100 mg.
Corn starch 50 mg.
Gelatin 7.5 mg.

~3~

Avicel (microcrystalline cellulose) 25 mg Magnesium stearate 2.5 mg.
185 mg.
are prepared (from sufficient bulk quanti-ties) by mixing the l-(3-mercapto-1-oxopropyl)-~-oxo-L-proline and corn starch with an aqueous solution of the gelatin. The mixture is dried and ground to a fine powder. The Avicel and then the magnesium stearate are admixed with granulation. This mixture is then compressed in a tablet press to form 1000 tablets each containing 100 mg. of active ingredient.
Examp~e 33 Tablets each containing 100 mg. of (S)-l-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline are produced as described in Example 32.
Example 34 1000 tablets each containing 50 mg. of 1-(3-mercapto l-oxopropyl)-4-oxo-L-proline are produced ~rom the following ingredients:
1-(3-mercapto-1-oxopropyl)-4-oxo-L-proline 50 g.
Lactose 100 g.
Avicel 150 g.
Corn starch 50 g Magnesium stearate 5 g.
The 1-~3-mercapto-1-oxopropyl)-4-oxo-L-proline, lactose, and Avicel are admixed, and then blended with corn starch. Magnesium stearate is added. The dry mixture is compressed in a tablet press to ~216 form 1000 355 mg. tablets each containing 50 mg. of active ingredient. The tablets are coated with a solution of Methocel E 15 (methyl cellulose~ including as a color a lake containi~g yellow ~5.
Example 35 Tablets each containirlg 50 mg. of (S)-l-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline are prepared as described in example 3~.
Example 36 -~wo piece ~1 gelatin capsules each containing 100 mg. of 1-(3-mercapto-1-oxopropyl)-4-oxo-L-proline, sodium salt, are filled with a mixture of the following ingredients:
1-(3-mercapto-1-oxopropyl)-4 oxo-L-proline 100 mg.
~agnesium stearate7 mg.
Lactose 193 mg.
Example 37 Gelatin capsules containing 100 mg. of (S)-l-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline, sodium salt are prepared as described in Example 36-Example 38 An injectable solution is produced as follows:
1-(3-mercapto-1-oxopropyl)-4-oxo-L-proline 500 g.
Methyl paraben 5 g.
Propyl paraben 1 g.
Sodium chloride 25 g.
Water for injection qs. 5 ~3~

The active substance, preservatives and sodium chloride are dissolved in 3 liters of water and then the volum~ is brought up to S liters. The solution is filtered through a sterile filter and aseptically filled into presterilized vials which are then closed with presterili~ed rubber closures.
Each vial contains 5 ml. of solution in a concentra-tion of lO0 mg. o active ingredient per ml. of solution for injection.
Example 39 An injection solution containing (S)-l-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline is prepared as described in Example 38.
Example 40 lS 6000 tablets each containing the following ingredients:
1-(3-mercapto-1-oxopropyl)-4-oxo-L-proline 100 my.
Avicel (microcry~talline cellulose) 100 mg.
Hydrochlorothiazide12.5 mg.
Lactose U.S.P.113 mg.
Corn starch U.S.P17.5 mg.
Stearic acid U.S.P~7 mg.
350 mg.
are produced from sufficient bulk quantities ~y slugging the l-(3-mercapto-1-oxopropyl)-4-oxo~L-proline, Avicel, and a portion of the stearic acid.
The slugs are ground and passed through a ~2 screen, then mixed with the hydrochlorothiazide, lactose, corn 8'~

-3~-starch and remainder of the stearic acid. The mixture is compressed into 350 mg. capsule shaped tablets in a tablet press. The tablets are scored for di~iding in half.
Exam~le41 -Tablets each containing (S)-l-(3-mercapto-2-methyl-l-oxopropyl)-4-oxo-L-proline and hydrochloro-thiazide can be prepared as described in Example 40.
The product of Examples l,3,5 to 25, and 27to 29 can be formulated according to the procedures of Examples 32-41.

Claims (20)

What is claimed is:

1. A process for preparing a keto-substituted proline or pipecolic acid of the formula or a physiologically acceptable salt thereof, wherein R is hydrogen or C1-C4 alkyl;
R1 and R3 are independently selected from the group consisting of hydrogen, C1-C4 alkyl, -CH2SH
or -CF3;
R2 is hydrogen or C1-C4 alkyl provided that R2 is C1-C4 alkyl only when R1 is C1-C4 alkyl;
m is zero, one or two;
p and q are each one or two provided that both are not two; and R4 is hydrogen or R5CO wherein R5 is C1-C4 alkyl or phenyl;
characterized by coupling a keto-substituted proline or pipecolic acid of the formula with an acid or its chemical equivalent of the formula and wherein R4 is R5CO-, hydrolyzing said product to form a product wherein R4 is hydrogen.

2. A process according to claim 1 wherein the product is of the formula

3. The process of claim 1 wherein R1 and R2 are both methyl.

4. The process of claim 1 wherein R2 is hydrogen; R1 is trifluoromethyl; and m is one.

5. The process of claim 1 wherein R2 is hydrogen; R1 is mercaptomethyl; and m is one.

6. The process of claim 1 wherein R1 and R2 are both hydrogen.

7. The process of claim 1 wherein R4 is hydrogen.

3. The process of claim 1 wherein R2 is hydrogen, R1 is methyl, and m is one.

9. The process of claim 1 wherein R2 is hydrogen, R1 is methyl, m is one and R4 is hydrogen.

10. The process of claim 1 wherein the product is (s)-1-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline.

11. A compound of the formula or a physiologically acceptable salt thereof, wherein R is hydrogen or C1-C4 alkyl;
R1 and R3 are independently selected from the group consisting of hydrogen, C1-C4 alkyl, -CH2SH
or -CF3;
R2 is hydrogen or C1-C4 alkyl provided that R2 is C1-C4 alkyl only when R1 is C1-C4 alkyl;
m is zero, one or two;
p and q are each one or two provided that both are not two; and R4 is hydrogen, or R5CO wherein R5 is C1-C4 alkyl or phenyl, whenever prepared by the process of claim 1.

12. A compound according to claim 11 of the formula whenever prepared by the process of claim 2.

13. The compound of claim 11 wherein R1 and R2 are both methyl, whenever prepared by the process of claim 3.

14. The compound of claim 11 wherein R2 is hydrogen; R1 is trifluoromethyl; and m is one, whenever prepared by the process of claim 4.

15. The compound of claim 11 wherein R2 is hydrogen; R1 is mercaptomethyl; and m is one, whenever prepared by the process of claim 5.

16. The compound of claim 11 wherein R1 and R2 are both hydrogen, whenever prepared by the process of claim 6.

17. The compound of claim 11wherein R4 is hydrogen, whenever prepared by the process of claim 7.

18. The compound of claim 11 wherein R2 is hydrogen, R1 is methyl, and m is one, whenever prepared by the process of claim 8.

19. The compound of claim 11 wherein R2 is hydrogen, R1 is methyl, m is one and R4 is hydrogen, whenever prepared by the process of claim 9.

20. The compound of claim 11, (S)-1-(3-mercapto-2-methyl-1-oxopropyl)-4-oxo-L-proline, whenever prepared by the process of claim 10.