CA1124723A - Halogen substituted mercaptoacylamino-prolines and pipecolic acids - Google Patents

Abstract

Abstract Compounds which have the general formula (I) wherein R is hydrogen, lower alkanoyl or m is 1 or 2; n is 0 or 1;
R1 is hydrogen or lower alkyl:
R2 and R'2 each is hydrogen or halogen;
R3 is hydrogen, lower alkyl or CF3, and also halogen when n is 1:
R4 is hydrogen, lower alkyl or trifluoromethyl:
R6 is hydrogen, and also halogen when m is 1;
at least one of R2, R'2, R3, R4 and R6 being halogen or CF3 as represented by the symbols and only R2 and R'2 can both be halogen at the same time, and basic salts thereof are useful as hypotensive agents.

Description

~ 23 HA162a-b Halogen Substltuted Mercaptoacylamino Acids This invention relates to new halogenated compounds which have the general formula (I) R2 ~ ~R'2 ~C ~
IR4 l3 H2~ (CHR6)m R- S -(CH)n- CH -CO CH-COOR

wherein R is hydrogen, lower alkanoyl or R R'

2 \ C / 2 /\~
14 iR3 H21C (CHR6)m -S - (CH)n - CH - CO - N CH-COOR
m is l or 2; n is 0 or l;
Rl is hydrogen or lower alkyli R2 and R'2 each is hydrogen or halgoen;
R3 is hydrogen, lower alkyl or CF3, and also halogen when n is l;
R4 is hydrogen, lower alkyl or trifluoromethyl;
R6 is hydrogen, and also halogen when m is l;
at least one of R2, R 2' R3, R4 a 6 halogen or CF3 as represented by the symbols and only R2 and R'2 can both be halogen at the same time.
The asteriskindicates anasymmetric carbon atom.

~ HA162a-b The invention in its broadest aspects relates to halogenated derivatives of mercaptoacyl proline and mercaptoacyl pipecolic acids having the formula I
above.
With respect to the prolines (when m is 1) two preferential groups of compounds within formula are those having the following formulas (II) i4 l3 R- S -(CH)n CH - CO - N COOR

wherein R is hydrogen. lower alkanoyl or IR4 ¦3 ~ ¦
-S - (CH)n - CH CO - N COOR

Rl is hydrogen or lower alkyl;
R2 and R5 each is hydrogen or fluorine;
R3 and R4 each is hydrogen or trifluoromethyl, one being hydrogen and the other trifluoro-methyl; and n is 0 or 1;
(III) R - S (CH)n- CH - CO - N COOR

,~3 ~ ~ ~ ~ HA162a-b wherein R and Rl have the same meaning as defined above for formula II;
R2 and R5 each is hydrogen or halogen;
R3 is hydrogen, halogen or lower alkyl, 5 R3 being halogen when both R2 and R5 are hydrogen, R3 being other than halogen when R2 or R5 is halogen;
R4 is hydrogen; and n is 0 or 1;
and basic salts of said compounds of formula II and III, respectively.
Thus in the case of formula II, when n is 0 and R2 and R5 are both hydrogen, R3 is trifluoromethyl.
When n is 1, either R3 or R4 is trifluoromethyl and the other is hydrogen. That is to say there is one trifluoromethyl group in the acyl side chain of the molecule. It is on the carbon ~ to the carbonyl group (R3 = CF3) when n is 0. It is on either the carbon a to the carbonyl group (R3 = CF3, R4 = H) or on the carbon ~ to the carbonyl group (R3 = H, R4 = CF3) when n is 1, the other of the pair of symbols (R3, R4) is then hydrogen. When either R3 or R4 is trifluoromethyl, R2 and R5 each is hydrogen or halogen.
In the case of formula III, preferably one or both of R2 and R5 are halogen and R3 and R4 each is hydrogen or lower alkyl, or both R2 and R5 are hydrogen, R3 is halogen, preferably chlorine or bromine, and R4 is hydrogen.
Preferred particularly are those compounds of formula I wherein R is hydrogen or lower alkanoyl, ~ 7~3 ~lA162a-b especially hydrogen or acetyl; Rl is hydrogen or lower alkyl, especially hydrogen; R2 and R5 each is hydrogen or halogen, especially hydrogen or fluorine;
R3 and R4 each is hydrogen, trifluoromethyl or lower alkyl, one of R3 or R4 being trifluoromethyl and the other hydrogen when R2, R5 and R6 are all hydrogen;
and n is 0 or 1, especially 1.
One or two halogens can be present on the pyrro-lidine ring. A single halogen can be on either the carbon in the 3-position or the carbon in the 4-position. Two halogens can be present in the 4-position and preferably they are the same. Fluorine is pre-ferred on this ring, especially one or two fluorine atoms on the carbon in the 4-position.
In the case of the pipecolic acids (m is 2), those compounds of formula I are preferred wherein R is hydrogen or lower alkanoyl, especially hydrogen or acetyl; Rl is hydrogen or lower alkyl, especially hydrogen; R2 and R'2 each is hydrogen or halogen especially hydrogen or fluorine; one of R3 and R4 is CF3 and the other is hydrogen; n is 0 or 1, especially 1. R2 and R'2 can independently be hydrogen or halogen, especially fluorine. When R3 or R4 is CF3, both R2 and R'2 are prefera~ly hydrogen.

The L-configuration for the prolines or pipecolic acids is especially preferred.
The lower alkyl groups represented by any of the variables include straight and branched chain hydro-carbon radicals from methyl to heptyl, for example, ~ 23 HA162a-b methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl and the like. The Cl-C4 members, especially Cl and C2 members, are preferred.
The lower alkanoyl groups are those having the acyl radicals of the lower (C2-C7) fatty acids, for example, acetyl, propionyl, butyryl and the like.
Similarly, those lower alkanoyl groups having up to four carbons, and especially acetyl, are preferred.
The halogens are the four common halogens, chlorine, bromine and fluorine being preferred, especially fluorine.
The products of formula I can be produced by various methods of synthesis.
In general, these compounds can be synthesized by coupling ~he acid of the formula (IV) R - S - (CH)n - CH COOH
to the amino acid of the formula (V) R2 R~2 \C
H2CI (CHR6)m HN---- CH COORl by any method which can be used to form amide bonds.
See, for example, "Methoden der Organischen Chemie"
(Houben-Weyl) part I, p. 376 et seq., part III, p. 1 et seq. (1974).

.

~ Z~23 HA16~a-b The acids of formula IV, when n is 1 can be obtained by the addition of a thioacid R-SH to a suitably substituted acrylic acid. As a temporary protection of the mercapto group in compounds of formula IV, R can be a p-methoxy-benzyl group. This group is then removed with trifluoroacetic acid and mercuric acetate. The acids of formula IV, when n is 0, are obtained by a displacement reaction using a thioacid R-SH and a 2-halo acid.
According to one method, preferred when n is 0, an acid of formula V is coupled with a halo-alkanoic acid of the formula (VI) Rl4 l3 X - (CH)n - CH-COOH

wherein X is halogen, preferably chlorine or bromine, by one of the known procedures in which the acid VI is activated, prior to reaction with the acid V, involving formation of a mixed anhydride, symmetrical anhydride, acid chloride, active ester, or use of Woodward reagent K, EEDQ (N-ethoxy-carbonyl-2-ethoxy-1,2-di-hydroquinoline) or the like.
The product of this reaction is a compound of the formula (VII) R2 X R'~

R4 13 H2C (CHR6)m X (CH)n - CH -CO - N OORl 1~3L24723 1-~16 2 a - b This product is subjected to a displacement reaction with the anion of a thioacid of the formula (VIII) R7-CO-SI~

wherein R7 is lower alkyl yielding a product of the formula (IX) X

R4 IR3 H21 I CHR6)m R7- CO -S - (CH)n CH- CO- N COOR

which can then be converted to the product (X) 2 ~ Rl2 IR4 IR3 H21C ~ (CHR6)m HS (CH)n C~- CO -N COOR
by conventional aIkaline hydrolysis or ammonolysis. When Rl is an ester group (i.e., Rl is lower alkyl, obtained when an ester of the starting acid V is used),the ester group can be removed by conventional techniques. For example, when Rl is tert-butoxy or tert-amyloxy, treatment of the es~er of formula IX or X with trifluoroacetic acid and anisole will give the corresponding free acid.
When other alkoxy groups are present alkaline hydrolysis will yield the corresponding acid.
When an acid of formula V is used as starting material, or the final product is obtained as the free carboxylic acid, this acid can be converted to its ester, for example, by esterification with a diazoalkane, like diazomethane, l-alkyl-3-p-tolyl-triazene, like l-n-butyl-3-p-tolyltriazene or the like.

~24~23 8 HA162a -b According to another variation, an ester, preferably the methyl or t-butyl ester, of formula V, in an anhydrous medium such as dichloromethane, tetrahydrofuran, dioxane or the like, is treated with an acylthioalkanoic acid of the formula (XI) R7 CO- S -(CH)n- CH - COOII
in the presence of dicyclohexylcarbodiimide, N,N'-carbonylbisimidazole, ethoxyacetylene, diphenylphosphoryl azide or similar coupling agents at a temperature in the range of about 0 to 10 C. The ester group can then be removed9 for example, by treatment with trifluoroacetic acid and anisole at about room temperature to yield the free acid (Rl = H).
A variation, preferred when n is 1, R4 is CF3 and R3 is H, is to react a thioacid of formula VIII
with an acrylic acid derivative of the formula (XII) R4 R3 R2 R '2 ~ H2 ~ CHR6)m CH _CH- C N- COORl instead of with the compound of formula VII, and then continue as described above. The compounds of formula XII are obtained from 3-trifluoromethyl-acrylic acid and an ester of formula V by the method described in Example 14 below.

~24723 9 HA162a-b Compounds of formula I wherein R is R2 R~2 ~4 l3 H2C ~C~R6)m -S - (CH)n- CH - CO - N COORl are produced by direct oxidation of a compound of formula I in which R is hydrogen, e.g., with iodine, to obtain the symmetrical bis compound.
Halogenated ~mpounds of formula V which are used as starting materials can be produced by methods known in the art, e.g., Biochemistry 4, 2509 (1965), Aust. J. Chem. 20, 1493 (1967), J. A~er. Chem. Soc. 86, 4709 (1964), J. Med Chem.
20, 1176 (1977).
Products of formula I have one or more asym-metric centers, the basic being indicated by an asterisk in formula I. The compounds accordingly exist in stereoisomeric forms or in racemic mixtures thereof. All of these are within the scope of the invention. The aboved described synthesis can utilize the racemate or one of the enantiomers as starting material. When the racemic starting material is used in the synthetic procedure, the stereoisomers obtained in the product can be separated by conventional chromatographic or fractional crystallization methods. In general, the L-isomer with respect to the basic asymmetric carbon constitutes the preferred isomeric form.
The compounds of this invention form basic salts with various inorganic and organic bases which are also within the scope of the invention. Such ~L~L24~23 10 HA162a-b salts include ammonium salts, alkali metal salts like sodium and potassium salts (which`are preferred), alkaline earth metal salts like the calcium and magnesium salts, salts with organic bases, e.g., dicyclohexylamine salts, benzathine, N-methyl-D-glucamine, hydrabamine salts, salts with amino acids like arginine, lysine and the like.
The non-toxic, physiologically acceptable salts are preferred, although other salts are also useful, e.g., in isolating or purifying the product.
The salts are formed in conventional manner by reacting the free acid form of the product with one or more equivalents of the appropriate base lS providing the desired salt ion, in a solvent or medium in which the salt is insoluble, or in water and removing the water by freeze drying. By neutralizing the salt with an insoluble acid like a cation exchange resin in the hydrogen form (e.g., polystyrene sulfonic acid resin like Dowex 50) or with an aqueous acid and extraction with an organic solvent, e.g., ethyl acetate, dichloromethane or the like, the free acid form can be obtained, and, if desired, another salt formed.
Additional experimental details are found in the examples which are preferred embodiments and also serve as models for the preparation of other members of the group.
The compounds of this invention are useful as hypotensive agents. They inhibit the conversion of the decapeptide angiotensin I to angiotensin II
and therefore are useful in reducing or relieving _ _ .

,: :

~l2'~23 11 ~162a-b angiotensin related hypertension. The action of the enzyme renin on angiotensinogen, a`pseudoglobulin 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 causative agent in various forms of hypertension in various mammalian species, e.g., rats and dogs. The compounds of this invention intervene in the angiotensinogen ~ (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 of formula I or a physiologically acceptable salt thereof, angiotensin dependent hypertension in the species of mammal suffering thereform is alleviated. A singledose, or prefera-bly two to four divided daily doses, provided on a basis of about 0.1 to 100 mg. per kilogram per day, preferably about 1 to 50 mg. per kilogram per day,is appropriate to reduce blood pressure as indicated in the animal model experiments described by S.L. Engel, T.R. Schaeffer, M. ~.Waugh and B. Rubin, Proc. Soc. Exp. Biol. Med. 143 (1973). The substance is preferably administered orally, but parenteral routes such as subcutaneously, intramuscularly, intravenously or intraperitoneally can also be employed.
The compounds of this invention can be utilized to achieve the reduction of blood pressure by 12 HA162a-b formulating in compositions such as tablets, capsules or elixirs for oral administration or in sterile solutions or suspensions for parenteral administration.
About 10 to 500 mg. of a compound or mixture of compounds of formula I or physiologically acceptable salt is compounded with a physiologically acceptable vehicle, carrier, excipient, binder, preservative, stabilizer, flavor, 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 of the adjuvants which may be incorporated in tablets, capsules and the like are the following: a binder such as gum tragacanth, acacia, corn starch or gelatin; an excipient such as dicalcium phosphate or microcrystalline cellulose;
a disintegrating agent such as corn starch, potato starch, alginic acid and the like, a lubricant ~0 such as magnesium stearate; a sweetening agent such as sucrose, lactose or saccharin; a flavoring agent such as peppermint, oil of wintergreen or cherry.
When the dosage unit form is a capsule, it may contain in addition to materials of the above type a liquid carrier such as a fatty oil. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablats may be coated with shellac, sugar or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propyl parabens as preservatives, a dye and a flavoring such as cherry or orange flavor.

:

13 HA162a-b Sterile compositions for injection can be formulated according to conventional pharmaceutical practice by dissolving or suspending the active substance in a vehicle such as water for injection, a naturally occurring vegetable oil like sesame oil, coconut oil, peanut oil, cottonseed oil, etc.
The following examples are illustrative of the invention and constitute especially preferred embodiments. All temperatures are in degrees Celsius.
Example 1

3-Acetylthio-2-trifluorome~
A mixture of thiolacetic acid (50 g.) and 2-(trifluoromethyl)acrylic acid [M.W. Buxton, et al.
J. Chem. Soc., 366 (1954)] (66 g. ) is heated on the steam bath for one hour and then stored at room temperature for eighteen hours. The reaction mixture is distilled in vacuo to give 3-acetylthio_2-trifluOromethylpropanoic acid.
Example 2 1-(3-Acetylthio-2-trifluoromethylpropanovl)-L-proline tert-butyl ester L-proline tert-butyl ester (5.1 g.) is dissolved in dichloromethane (40 mg.) and the solution is stirred and chilled in an ice bath. Dicyclohexyl-carbodiimide (6.q g.) dissolved in dichloromethane (15 ml.) is added followed immediately by a solution of 3-acetylthio-2-trifluoromethylp~opanoic acid (6.5 g.) in dichloromethane (5 ml.). After fifteen minutes stirring in the ice bath and sixteen hours at room temperature, the precipitate formed is filtered off and the filtrate is . .
' ;' -14 HA162a-b concentrated to dryness in vacuo. The residue is dissolved in ethyl acetate and washed nèutral. The organic phase is dried over magnesium sulfate and concentrated to dryness in vacuo to give l-(3-acetyl-thio-2-trifluoromethylpropanoyl)-L-proline tert-butyl ester.
Example 3 1-(3-Acetylthio-2-trifluoromethylpropanoyl)-L-proline 1-(3-Acetylthio-2-trifluoromethylpropanoyl)-L-proline tert-butyl ester (8 g.) is dissolved in a mixture of anisole (55 ml.) and trifluoroacetic acid (110 ml.). After one hour storage at room temperature the solvent is removed in vacuo and the residue is precipitated several times from ether-hexane to give 1-(3-acetylthio-2-trifluoromethyl-propanoyl)-L-proline.
Example 4 1-(3-Mercapto-2-trifluoromethylpropanoyl)-L-proline 1-(3-Acetylthio-2-trifluoromethylpropanoyl)-L-proline (4 g.) is dissolved in a mixture of water (8 ml.) and concentrated ammonia (8 ml.) under a blanket of nitrogen. After twenty-five minutes stirring at room temperature, the reaction mixture is chilled, acidified and extracted with ethyl acetate. The organic layer is concentrated to dryness in vacuo to yield l-(3-mercapto-2 trifluoro-methylpropanoyl)-L-proline.
Example 5 2-Bromo-3,3,3-trifluoropropanoic acid 3,3,3-Trifluoroalanine (88 g.) is dissolved in a mixture of potassium bromide (250 g.) and 2.5 N
sulfl~ric acid (1.240 ml.). The solution is chilled ~247`23 15 HA162a~b to 0 with an ice-salt bath and sodium nitrite (65.5 g.) is added in small portions over a one hour period with vigorous stirring. The reaction mixture is stirred in the cooling bath for another hour and then extracted with ether. The organic layer is washed with water, dried over magnesium sulfate and concentrated to dryness in vacuo to yield 2-bromo-3,3,3-trifluoropropanoic acid.
Example 6 2-Bromo-3,3,3-trifluoropropanoic acid chloride A solution of 2-bromo-3,3,3-trifluoropropanoic acid (5 g.) in thionyl chloride (5 ml.) is refluxed in the steam bath for two hours. The excess thionyl chloride is removed in vacuo, and the residue distilled under reduced pressure to yield 2-bromo-3,3,3-trifluoropropanoic acid chloride.
Exam~le 7 1-(2-Acetylthio-3~3~3-trifluoropropanoyl)-L-proline To a solution of L-proline (5.75 g.) in lN
sodium hydroxide (50 ml.), chilled in an ice-water bath, 2-bromo-3,3,3-trifluoropropanoic acid chloride (12 g.) is added and the mixture is vigorously stirred at room temperature for three hours. A solution of thiolacetic acid (4 ml.) and potassium carbonate (4.8 g.) in water (50 ml.) is added and the mixture is stirred at room temperature for sixteen hours. After extraetion with ethyl acetate, the aqueous layer is acidified with concentrated hydrochloric acid and extracted again with ethyl acetate. This last organie phase is dried over maynesium sulfate and concentrated to dryness in vacuo. The residue is ehromatographed 16 HA162a-b on a silica gel column with a mixture of benzene-acetic acid (7:2) to yield 1-(2-acetylthio-3,3,3-trifluoropropanoyl)-L-proline.
Example 8 1-(2-Mercapto-3,3,3-trifluoropropanoyl)-L-proline 1-(2-Acetylthio-3,3,3-trifluoropropanoyl)-L-proline (4 g.) is dissolved in a mixture of water (8 ml.) and concentrated ammonia (8 ml.) under a blanket of nitrogen. After thirty minutes at room temperature, the reaction mixture is acidified and extracted with ethyl acetate. The organic phase is dried over magnesium sulfate and concentrated to dryness in vacuo to yield l-(2-mercapto-3,3,3-tri-fluoropropanoyl)-L-proline.
Example 9 1,1'-[Dithiobis-(2-trifluoromethyl-3-propanoyl)]-bis-L-proline 1-(3-Mercapto--2-trifluoromethylpropanoyl)-L-proline (1 g.) is dissolved in water adjusted to 2C pH 7 with N sodium hydroxide. An ethanolic solution of iodine is added dropwise while maintaining the pH
between 6 and 7 by careful addition of N sodium hydroxide. When a permanent yellow color is obtained, the addition o iodine is stopped and the color is discharged with sodium thiosulfate. The reaction mixture is acidified and extracted with ethyl acetate. The organic layer is dried over magnesium sulfate and concentrated to dryness to yield l,l'-[dithiobis-(2-trifluoromethyl-3-propanoyl)~-bis-L-proline.

,.... .

17 IIA1~2a-b _ample 10 1-(3-~cetylthio-2-trifluoromethylpropanoyl)-L-proline sodium salt A suspension of 1-(3-acetylthio-2-trifluoro-methylpropanoyl)-L-proline (1 g.) in water (10 ml.) is adjusted to pH 8 by addition of normal sodium hydroxide. The resulting solution is freeze dried to yield l-(3-acetylthio-2-trifluoromethylpropanoyl)-L-proline sodium salt.
Example 11 1-(3-Acetylthio-2-trifluoromethylpropanoyl)-4,4-difluoro-L-proline To a solution of 4,4-difluoro-2-proline (7.5 g.) in N sodium hydroxide (50 ml.) chilled in an ice-water bath, 3-acetylthio-2-trifluoro-methylpropanoic acid chloride (prepared from 3-acetylthio-2-trifluoromethylpropanoic acid and thionyl chloride by the procedure of Example 6,) ~2 g.)is added and the mixture is vigorously stirred at room temperature for two hours. After acidifica-tion with concentrated hydrochloric acid, the aqueous mixture is extracted with ethyl acetate. The organic phase is dried over magnesium sulfate and concentra-ted to dryness to yield l-(3-acetylthio-2-trifluoro-methylpropanoyl)-4,4-difluoro-L-proline.
Example 12 1-(3-Mercapt.o-2-trifluoromethxlpropanoyl)-4,4-difluoro-L-proline By substituting 1-(3-acetylthio-2-trifluoromethyl-propanoyl)-4,4-difluoro-L-proline for the 1-(3-acetylthio-2-trifluoromethylpropanoyl)-L-proline in the procedure of Example 4, 1-(3-mercapto-2-trifluoro-_ _ 18 IIA162a-b methylpropanoyl)-4,4-difluoro-L-proline is obtained.
Example 13 1,1'-[Dithlobis-(2-trifluoromethyl-3-propanoyl)~-bis-4,4-difluoro-L-proline By substituting 1-(3-mercapto-2-trifluoro-methylpropanoyl)-4,4 difluoro-L-proline for the 1-(3-mercapto-2-trifluoromethylpropanoyl)-L-proline in the procedure of Example 9, 1,1-~dithiobis-(2-trifluoromethyl-3-propanoyl)]-bis-

4,4-difluoro-L-proline is obtained.
Example 14 1-(4,4,4-Trifluoro-2-butenoyl)-L-proline Boric anhydride (7.0 g., 0.1 mole)(prepared by fusing boric acid in a platinum crucible and crushing under nitrogen)is combined with ethyl 3-hydroxy-4,4,4-trifluorobutanoate (32.2 g., 0.173 mole) in a 50 ml. flask equipped with a Dean-Stark trap and the mixture is heated at 180 with a salt bath until all of the anhydride dissolves (6 hours). The heat is increased to 350 during which time 23 ml. of distillate accumulates in the trap. The distillate is returned to the reaction flask and the heating step is repeated. This process is repeated 4 times to assure complete dehydration of the hydroxy ester.
The distillate is dissolved in petroleum ether, dried over phosphorous pentoxide and distilled, yielding 10 g. of 4,4,4-trifluoro-2-butenoic acid ethyl ester (b.p. 115-120 ) and 650 mg. of 4,4,4-trifluoro-2-butenoic acid (b.p. 150 , 53-55 recrystallization from pentane).

~12 ~23 19 HR162a-b The ester is combined with 10% aqueous sodium hydroxide (24 ml.) and stirred at 25 for 6 hours.
The mixture is diluted with water and extracted with methylene chloride to remove unchanged material.
The aqueous layer is adjusted to pH 3 with concentra-ted hydrochloric acid and this mixture is extracted with methylene chloride ( 3 x 50 ml.). The organic layers are combined, dried over sodium sulfate, concentrated and the residue dis-tilled giving crysta-lline 4,4,4-trifluoro-2-butenoic acid (b.p. 145-153 ).
Recrystallized from pentane, the acid melts at 54-55 , yield 4.6 g.
A mixture of the 4,4,4-trifluoro-2-butenoic acid (4.91 g., 35 mmole), hydroxybenzotriazole (4.73 g., 35 mmole), L-proline-t-butyl ester (6.00 g., 35 mmole) and dicyclohexylcarbodiimide (7.22 g., 35 mmole) in methylene chloride (200 ml.) is stirred under nitrogen overnight at room tempera-ture. The mixture is filtered, the filtrate washed with 5~ sodium bisulfate (2 x 50 ml.) and saturated sodium bicarbonate (2 x 50 ml.), dried over sodium sulfate and concentrated to yield an oil. This is dissolved in ether and the solution is chilled and filtered free of precipitate. The filtrate is concentrated, yielding a solid ( m.p. 95-100, 8.7 g.) which shows a single spo-t by TLC (silica gel EM 50/50, EtoAc~CH2C12, Rf = .85).
A mixture of the above obtained 1-(4,4,4-tri-fluoro-2-butenoyl)-L-proline t-butyl ester (4.0 g., 13.6 mmole) is mixed with trifluoroacetic acid (60 ml.) and anisole (13 ml.) and stirred under nitrogen for one hour. The solvents are removed 20 H~162a-b under vacuum and the residue, dissolved in ether (10 ml.), is poured into pentane (500 ml.). This precipitatiOn technique is repeated and the residue allowed to stand at 0 for 72 hours during which time crystallization occurs. The 1-(4,4,4-trifluoro-2-butenoyl) L-proline is recrystallized from ethyl acetate-hexane; yield 2.48 g., m.p.
119-120 .
Example 15 1-(3-Mercapto-4,4,4-trifluorobutanoyl)-L-proline Thiolacetic acid (1.5 ml.) is combined with 1-(4,4,4-trifluoro-2-butenoyl)-L-proline (720 mg., 3 mmole) under argon and the mixture stirred at room temperature overnight. The excess thiol-acetic acid is removed under vacuum and the residual l-(3-acetylthio-4,4,4-trifluorobutanoyl)-L-proline is mixed with aqueous ammonia (15 ml.
conc. NH3 ~ 15 ml. water) and stirred for 2 hours at room temperature. The mixture is then diluted with ice and acidified with concentrated hydrochloric acid. The acid mixture is extracted with methylene chloride (3 x 50 ml.), the extracts dried over sodium sulfate and concentrated to yield an oil. This is purified by dissolving in water (double distilled), treating the solution with carbon and filtering through a millipore filter (0.4 m followed by 0.08 m). Lyophilization of this solution gives 700 mg. of 1-(3-mercapto-4,4,4-trifluorobutanoyl)-L-proline as a colorless glass.
Rf (benzene:acetic acid 7:1) 0.24 ,, ,~ .

21 HA162a~b Example 16 3~Acet lthio-4,4,4-trifluorobutanoic acid chloride Y
By substituting 4,4,4-trifluoro-2-butenoic acid for the 2-trifluoromethyl acrylic acid in the -procedure of Example 1, 3-acetylthio-4,4,4-trifluoro-butanoic acid is obtained, then chlorinating with thionyl chloride as in Example 6, 3-acetylthio-4,4,4-trifluorobutanoic acid chloride is obtained.
Example 17 1-(3-Mercapto-4,4,4-trifluorobutanoyl)-4,q-difluoro-L-proline By substituting 1--(3-acetylthio-4,4,4-trifluoro-butanoic acid chloride for the 3-acetylthio-2-trifluoromethylpropanoic acid chloride in the procedure of-Example 11 and then submitting the product ~to the proced~re of Example 4, 1-(3-mercapto-4,4,4-tri.fluorobutanoyl)-4,.4-difluoro-L-proline is obtained.
Example 18 o 1 1'-[Dithiobis-(4,4,4-tri~luoro-3-butanoyl)]-bis-L-2 ~ _ proline By substituting 1-(3-mercapto-4,4,4-trifluoro-butanoyl)-L-Proline for the 1-(3-mercapto-2-trifluoro-methylpropanoyl)-L-proline in the procedure of Example 9, 1,1'-[dithiobis-(4,4,4-trifluoro-3-butanoyl)]-bis-L-proline is obtained.
Example 19 cis-4-Fluoro-L-Proline, hydrobromide a) N-Carbobenzylox~-4-hydroxy-L-proline, methyl ester N-Carbobenzyloxy-4-hydroxy-L-proline [12.4 g.
(0.047 mole)] is esterified with diazomethane in dioxane-ether as described in JACS, 79, 191 (1957).

.1~!L~L~7~ ~

22 HA162a-b To avoid freezing of the dioxane the addition of the diazomethane solution is begun at 10 and completed at 0-2 . The yield of nearly colorless viscous oil is 14.6 g. (100%).
b) N-Carbobenæyloxy-4~tosyloxy-L-proline, methyl ester A stirred solution of 14.5 g. (0.052 mole) of N-carbobenzyloxy-4-hydroxy-L-proline, methyl ester in 30 ml. of pyridine is treated dropwise at -5 to -8 with a solution of 11 g. (0.058 mole) of tosyl chloride in 15 ml. of pyridine. The pale yellow solution is stored in the cold for 3 days, then added with stirring to 300 ml. of ice-cold 2 N
hydrochloric acid. The precipitated gum is extracted with 200 ml. of chloroform. The aqueous phase is extracted with additional chloroform (3 x 100 ml.). The organic layers are combined, dried (MgSO4), and the solvent evaporated to give a pale yellow viscous oil. The oil is dissolved in 100 ml. of methanol and diluted to 400 ml. with water to precipitate the product as an oil which gradually crystallizes on seeding, xubbing, and cooling: yield 17.4 g. (77%); m.p. 62-65.
Following crystallization from 85 ml. of isopropanol, the colorless solid N-carbobenzyloxy-4-tosyloxy-L-proline, methyl ester weighs 15.9 g. (70%);
m p 67-69; [a]26 _30 ( c = l; methanol).
c) cis-N-CarbobenzvloxY-4-fluoro-L-proline, methyl ester A stirred suspension of 19.1 g. (0.044 mole) of N-carbobenzyloxy-4-tosyloxy-L-proline, methyl ester in 100 ml. of redistilled diethylene glycol is treated at 42 (under argon) with 19.1 g.

.: :

"

7;~3 23 l~ 2a-b (0.33 mole) of anhydrous potassium ~luoride and the resulting solution is heated at 81`84 for 20 hours. After cooling, the light yellow solution is worked up to give 18.6 g. (100%) of cis-N-carbobenzyloxy-4-fluoro-L-proline, methyl ester as a light yellow oil.
d) cis-N-Carbobenzyloxy -4-fluoro-L-proline The cis-N-carbobenzyloxy-4-fluoro-L-proline, methyl ester (18.4 g., approximately 0.044 mole) is dissolved in 140 ml. of methanol, treated drop-wise at -1 to 4 with 33 ml. (0.066 mole) of 2 N sodium hydroxide, then kept at 0 for one hour, and at room temperature overnight. After removing about 1/2 of the solvent on a rotary evaporator, the solution is diluted with 300 ml. of water, washed with ether (wash discarded), acidified while cooling with 12.5 ml. of 1:1 hydrochloric acid to pH 2, and extracted with ethyl acetate (4 x 150 ml.).
The extracts are combined, washed with 100 ml. of saturated sodium chloride solution, dried (MgSO4) and the solvent evaporated to give 13.8 g. of a pale yellow viscous oil. The latter is dissolved in 60 ml. of ethanol, treated with 5.1 g. of cyclo-hexylamine in 10 ml. of ethanol and diluted to 900 ml. with ether. On seeding and rubbing, crystalline cis-N-carbobenzyloxy-4-fluoro-L-proline, cyclohexylamine salt separates: weight after cooling overnight, 11.0 g., m.p. 180-183 (s. 175 ).
Following crystallization from 70 ml. of ethanol, the colorless solid weighs 7.6 g., m~p. 185-187, [a]D ~40 ~c = 1; methanol).

. :...... - -24 ~l~162a -b The cyclohexylamine salt is suspended in 75 ml.
of ethyl acetate, stirred, and treated with 45 ml.
of hydrochloric acid. The layers are separated, the aqueous phase is extracted with additional ethyl acetate (2 x 75 ml.), then the combined organic layers are dried (MgSO4), and the solvent evaporated.
The residual free acid, cis-N-carbobenzyloxy-4-fluoro-L-proline crystallizes when finally dried at 0.2 mm. and 45 ; yield 5.7 g. (49~); m.p.
116-118 .
e) cis-4-Fluoro-L-proline, hydrobromide The cis-N-carbobenzyloxy-4-fluoro-L-proline (5.5 g., 0.021 mole) is treated with 28 ml. of hydrogen bromide in acetic acid (30-32%), stoppered looselY, and stirred for one hour. Ether (300 ml.) is added to the yellow mixture and when the crystalline product has settled the ethereal liquor is decanted and the material washed with 300 ml.
of fresh ether by decantation. The product is finally heated in the steam bath with 70 ml. of methyl ethyl ketone, cooled for two hours, washed with cold methyl ethyl ketone and with ether, and dried in vacuo. The yield of nearly colorless solid, cis-4-fluoro-L-proline, hydrobromide is 3.8 g. (86%), m.p. 189-191 (dec.), [a]D -19 (c = 1, methanol).
A portion of the crude hydrobromide salt is converted to the free acid by passing through a column of Dowex l-X8 ion exchange resin.

,~. .~ .

:

25 HAl62a-b Example 20 ci~ [l)-3- A_etylthio)-2-1ne~l~yll~ro~ n~ -4-fluoro-L-prolinc cis-4-Fluoro-L-proline, hydrobromide (4.5 g., 0.021 mole) and 4.2 g. (0.023 mole) of D-3-acetyl-thio-2-methylpropanoic acid chloride are reacted in 50 ml. of water in the presence of sodium carbonate to stabilize the pH at 8.0 - 8.2 during the acylation (approximately 20 minutes). The mixture is worked up after an additional hour by washing with ethyl acetate (2 x 50 ml.),layering over with ethyl acetate, acidifying with hydrochloric acid to pH 2, saturating with sodium chloride and then separating the layers. The aqueous phase is extracted with additional ethyl acetate and the organic layers are combined, dried and evaporated. The solid residue from the ethyl acetate evaporation is rubbed under ether and the evaporation repeated; weight of colorless product, 5.4 g. (93%), m.p. 146-148 (s.133 ) [~26 -132 (c = l; methanol). The dicyclohexylamine salt is prepared by adding dicyclohexylamine to the cis-l-[D-3-(acetylthio)-2-methylpropanoyl-4-fluoro-L-proline in 70 ml. of ethyl acetate. 8.1 gm. of salt, which crystallizes out, are obtained, m.p.
202-204 ~s. 187); [a]2 -72 (c = l; methanol).
Crystallization from 90 ml. o~ isopropanol gives 7.0 g., m.p. 205-207 ~s, 190). [a]26 -74.
A sa~ple recrystallized from ethanol shows no further change in m.p. of []D
The dicyclohexylamine salt (16.9 g.) is con-verted back to the free acid by distribution between 10~ potassium bisulfate and ethyl acetate (60 ml.

... . .

;23 26 1lA162a-b 10% KHSO4i 4 x 50 ml. ethyl acetate extractions).
The organic layers are combined and evaporated to dryness to obtain 4.1 g. (71~) of colorless free acid, m.p. 154-156 (s. 140 ) [a]D6 -142 (c = 1; methanol).
Example 21 cis-4-Fluoro-l-(D-3-mercapto-2-methyl~roPanoyl)-L-..
prolinecis-l-lD-3-(Acetvlthio)-2-methylpropanoyl]-4-fluoro-L-proline (3.9 g., 0.014 mole) is hydrolyzed in 22 ml. of water containing 9 ml. of concentrated ammonium hydroxide. The reaction mixture is acidified with hydrochloric acid and extracted with ethyl acetate. The organic layer is concentrated to dryness to give 3.3 g. of glass-like product which slowly crystallizes when dried at 0.2 mm. and 50 . The material is triturated with 20 ml. of ethyl acetate (with slight warming under argon), diluted with 25 ml. of h~xane, rubbed, and cooled overnight (under argon). Following filtration under argon, washing with hexane, and drying in vacuo, the colorless solid cis-4-fluoro-1-(D-3-mercapto-2-methylpropanoyl)-L-proline weighs 2.8 g. (85~), m.p. 135-137 (s. 129), [~]26 -116 (c = l; methanol).
Example 22 1-[3-(Acetylthio)-2-chloropropanoyl]-L-proline (Isomer A) L-Proline (1.44 g.) and sodium carbonate (667 mg.) are dissolved in 17 ml. of water and stirred in an ice bath. To this sodium carbonate (2 g.) in 8.5 mg. of water is added, followed immediately by 3-acetylthio-2-chloropropanoic acid chloride (2.5 g.).

~%3 27 HA162a~b The ice bath is removed. After 30 minutes a precipi-tate forms which is solubilized with thè addition of 17 ml. of water. After a total of 1.5 hours, the reaction mixture is extracted twice with ethyl acetate.
The aqueous layer is chilled, acidified with concen-trated hydrochloric acid, saturated with sodium chloride, extracted into ethyl acetate, dried over magnesium sulfate and concentrated to dryness in vacuo to obtain the product as a crude oil, yield 3.3 g.
The oil is applied to a 100 g. silica gel column and eluted with benzene/acetic acid 7:1 to yield 2 g. of product which is crystallized from water to yield 450 mg. of 1-[3-(acetylthio)-2-chloro-propanoyl]-L-proline, m.p. 111-113 . [a] -170 lS tc = 1; ethanol) Example 23 1-[3-(Acetylthio)-2-chloroeropanoyl]-L-proline (Isomer B) -The aqueous mother liquors from Example 22 are lyophilized and chromatographed on silica gel with benzene/acetic acid 7:1. The fractions containing the UV absorbing material and shown to be homogensous by TLC are pooled, concentrated to dryness and crystallized from water, yield 800 mg., m.p. 90-109 [a]D -4 (c = 2.1; ethanol). The mother liquors are concentrated to dryness by freeze-drying and the residual l-[3-(acetylthio)-2-chloropropanoyl-L
proline, (Isomer B) is crystallized from ether-hexane; yield 380 mg., m.p. 108-110 , [a]D +17.6 (c = 1.25; ethanol).

;1~i 2'~

28 HA162a-b Example 24 .
1-[3-(Acetylthio)-2-bromopropanovl]-L-proline , By substituting 3-acetylthio-2-bromopropanoic acid chloride for the 3-acetylthio-2-chloropropanoic acid chloride in the procedure of Example 22, 1-[3-(acetylthio)-2-bromopropanoyl]-L-proline is obtained, m.p. 109-110 , [a]D -162 (c = 1.39;
ethanol).
~xample 25 cis-4-Chloro-l-(D-3-mercapto-2-methylpropanoyl-L-proline By substituting cis-4-chloro-L-proline [Aust.
J. Chem. 20, 1493 (1967)] for the cis-4-fluoro-L-proline, hydrobromide in the procedure of Example 20, and then submitting the product to the procedure of Example 21, cis-1-[D-3-(acetylthio)-2-methyl-propanoyl-4-chloroproline and cis-4-chloro-1-(D-3-mercapto-2-methylpropanoyl)-L-proline are obtained.
Example 26 trans-4-Bromo-l-(D-3-mercapto-2-methylpropanoyl)-L
proline By substituting trans-4-bromo-L-proline lAust.
J. Chem. 20, 1493 (1967)] for the cis-4-fluoro-L-proline hydrobromide in the procedure of Example 20, and then submitting the product to the procedure of Example 21, trans-1-[D-3-(acetylthio)-2-methylpro-panoyl}-4-bromo-L-proline and trans-4-bromo-1-(D-3-mercapto-2-methylpropanoyl)-L-proline are obtained.
Example 27 By substituting cis-4-iodo-L-proline for the cis-4-fluoro-L-proline hydrobromide in the procedure ., .

.
.

~, HA16;2a-b of Example 20, and then submitting the product to the procedure of Example 21, cis-1-ED-3-(acetylthio)-2-methylpropanoyl-4-iodo-L-proline, and cis 4-iodo-l-[D-3-mercapto-2-methylpropanoyl]-L-proline are obtained.
Example 28 cis-4-Fluoro-1-~3-mercapto-2-trifluoromethylpropanoyl)-L-proline By substituting 3-acetylthio-2-trifluoromethyl-propanoic acid chloride for the 3-acetylthio-2-methyl-propanoic acid chloride in the procedure of Example 20 and then submitting the product to the procedure of Example 21, cis-1-13-(acetylthio)-2-trifluoro-methylpropanoyl]-4-fluoro-L-proline and cis-4-fluoro-1-(3-mercapto-2-trifluoromethylpropanoyl)-L-proline, respectively, are obtained.
Example 29 cis-3-Fluoro-DL-proline, hydrobromide By substituting ~-carbobenzyloxy-3-hydroxy-DL-proline [J. ~m. Chem. Soc. 85, 2824 (1963)1 for the N-carbobenzyloxy-4-hydroxy-L-proline in the procedure of Example 19, cis-3-fluoro-DL-proline hydrobromide is obtained, ~ Example 30 ; 25 cis-3-Fluoro-l-(D-3-mercapto-2-methylpropanoyl-DL-proline By substituting cis-3-fluoro-DL-proline hydro-bromide for the cis-4-fluoro-DL-proline in the pro-cedure of Example 20 and then submitting the product to the procedure of Example 21, cis-1-~D-3-(acetylthio)-2-methylpropanoyll-3-fluoro-DL-proline and cis-3-fluoro-l-(D-3-mercapto-2-methylpropanoyl)-DL-proline are obtained.

~1~ 3 30 ~IA162a-b Examplc 31 cis-3-Chloro-l-(D-3-mercapto-2-mcthylpropanoyl-L-proline By substituting cis-3-chloro-L-proline [obtained from 3-hydroxyproline by the procedure described in Aust. J. Chem. _, 1493 (1967)] for the cis-4-fluoro-L-proline hydrobromide in the procedure of Example 20 and then submitting the product to the procedure of Example 21, cis-1-[D-3-(acetylthio)-2-methylpropanoyl-3-chloro-L-proline, and cis-3-ahloro-l-(D 3-mercapto-2-methylpropanoyl)-L-proline are obtained.
Example 32 4,4-Dichloro-l-(D-3-mercapto-2-methylpropanoyl)-L-proline By substituting 4,4-dichloro-L-proline [prepared from 4-keto-L-proline diketopiperazine and phos-phorus pentachloride by the procedure described in J. Med. Chem. 20, 1176 (1977)] for the cis-4-fluoro-L-proline hydrobromide in the procedure of Example 20, and then submitting the product to the procedure of Example 21, 1-[D-3-(acetylthio)-2-methylpropanoyl]-4, 4-dichloro-L-proline and 4,4-dichloro-1-(D-3-mercapto-2-methylpropanoyl)-L-proline are obtained.
Example 33 1,1'-[Dithiobis-(2-D-methylpropanoyl)]-bis-[(cis-4-fluoro)-L-pro_ine]
By substituting cis-4-fluoro-1-(D-3-mercapto-2-methylpropanoyl)-L-proline for the 1-(3-mercapto-2-trifluoromethylpropanoyl)-L-proline in the pro-cedure of Example 9, 1,1'-[dithiobis-(2-D-methyl-propanoyl)]-bis-[(cis-4-fluoro)-L-proline] is obtained.

-3 ~2~
31 ~-IA162a-b Example 34 4,4-Difl _ro-1-(3-merca~>tol_tanoyl)-1,-Lroline By substituting 3-acetylthiobutanoic acid chloride for the 3-acetylthio-2-trifluoromethyl-propanoic acid chloride in the procedure of Example 11 and then submitting the product to the procedure of Example 12, 1-(3-acetylthio-butanoyl)-4,4-difluoro-L-proline and 4,4-difluoro-1-(3-mercaptobutanoyl)-L-proline are obtained.
Example 35 1-(3-Propanoylthio-2-trifluoromethylpropanoyl)-L-proline By substituting thiopropanoic acid for the thioacetic acid in the procedure of Example 1 and then submitting the product to the procedures of Examples 2 and 3, 3-propanoylthio-2-trifluoro-methylpropanoic acid, 1-(3-propanoylthio-2-trifluoromethylpropanoyl)-L-proline tert butyl ester and l-(3-propanoylthio-2-trifluoromethyl-propanoyl)-L-proline, respectively, are obtained.
Example 36 3-(4-Methoxybenzyl)thio-2-trifluoromethylpropanoic acid A neat mixture of l-trifluoromethylacrylic acid (3.9 g.) and 4-methoxybenzylthiol (4.3 g.) is stirred at 100-110 for one hour. The mixture is allowed to cool to room temperature and the solid is recrystallized from cyclohexane, m.p. 72-74 .
Example 37 1-~3-(4-Methoxybenzyl)thio-2-tr oyl~-L-proline tert-butyl ester -A solution of 3-(4-methoxybenzyl)thio-2-trifluoro-methylpropanoic acid (6.5 g.) and proline tert-butyl ester (3.76 g.) in dichloromethane (500 ml.) ~ ~ .

1~2~7%3 ~IA162a-b is stirred at 0 and treated with dicyclohexylcarbodi-imide (4.53 g.). After 30 ~linutes at 0 and over-night at room temperature, the mixture is filtered and the filtrate is washed neutral. The organic layer is dried and concentrated to dryness in vacuo.
The TLC [silica gel methylene chloride/ethyl3 acetate (95:5)] shows two major spots Rf 0.46 and 0.51 corresponding to the two diastereoisomers.
Example 38 1-(3-Mercapto-2-trifluoromethylpropanoyl)-L-proline A solution of 1-[3-(4-methoxybenzyl)thio-2-trifluoromethylpropanoyl]-L-proline tert-butyl ester (4.47 g.) obtained in Example 37 and anisole (10 ml.) is cooled to 0 and trifluoroacetic acid (100 ml.) is added, followed by mercuric acetate (3.18 g.).
The bath is removed and the mixture is stirred at room temperature for one hour. The mixture is concentrated to dryness in vacuo and the residue is triturated with ether-hexane. The insoluble material is suspended in water and hydrogen sulfide is bubbled through for 10 minutes. The precipitate is removed by filtration and the filtrate is freeze dried to give the product, ~-(3-mercapto-2-trifluoromethylpropanoyl)-L-proline as an amorphous solid. Rf 0.29 - 0.31 (silica gel-benzene:acetic acid 7:1).
Example 393-Acetylthio-2-chloropropanoic acid chloride By substituting 2-ahloroacrylic acid for the 2-trifluoromethylacrylic acid in the procedure of Example 1 and then allowing the product to react with thionyl chloride, 3-acetylthio-2-chloropropanoic acid and 3-acetylthio-2-chloropropanoic acid chloride are obtained.

,,, 1~4723 33 ElAl62a-b Example 40 D-3-Acetylthio-2-methylpropanoic acid chloride A suspension of l-(D-3-mercapto-2-methylpropan-oyl)-L-proline, (150 g. 690 mmoles), in 1274 ml.
of water and 426 ml. of concentrated hydrochloric acid (5.526 moles) is refluxed under nitrogen with stirring for 8 hours. The resulting solution is kept at room temperature overnight and then extracted with 400 ml. of chloroform (10 x). The combined chloroform extracts are dried over magnesium sulfate under nitrogen and then evaporated.
To the residue, 81.2 g. is added acetic anhydride, (176 ml., 1.809 mole), and pyridine, 180 ml., and the mixture is kept at room temperature for 20 hours.
The mixture is then evaporated and the oily residue is dissolved in 1000 ml. of ethyl acetate and the solution is washed in sequence with 200 ml.

5% hydrochloric acid-saturated sodium chloride (washing pH 2), 200 ml. of saturated sodium chloride solution (2 times, second washing pH 7) and then stripped of the solvent. To the clear oily residue, [96.9 g., 86.5~, had [a]D = -61.8 (CE~C13)]is added freshly distilled thionyl chloride, (83 ml., 1.173 mole) and the resulting solution is stirred at room temperature with evolution of gas for 18 hours. The excess thionyl chloride is evaporated under vacuum and a 50 bath and the 3~ residue is distilled at reduced pressure to obtain 56.9 g. of D-3-acetylthio-2-methylpropanoic acid chloride, b.p. 40-4 (0.17 -0.2 mm Hg.) [ ]25 -42.5 (c 2; methanol).

~ .

~.~.~7~ A 1 ~) 2 ~ - ~

Example 41 3-Acetylthio-2-bromopropanoic acid chloride By substituting 2-bromoacrylic acid for the 2-trifluoromethylacrylic acid in the procedure of Example 1 and then allowing the product to react with thionyl chloride, 3-acetylthio-2-bromopropanoic acid and 3-acetylthio-2-bromopropanoic acid chloride are obtained.
~xample 42 Trans-1-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4-fluoro-L-proline A) Trans-l-carbobenzyloxy-4-fluoro-L-proline A solution of 6.2 grams of trans-l-carbobenzyloxy-4-fluoro-L-proline, methyl ester in 50 ml of methanol is treated dropwise a~ 0-5, with 11.5 ml of 2N
sodium hydroxide solution, and after 1 hour at 0, allowed to warm to room temperature overnight. mhe reaction mixture is concentrated under reduced pressure to about one-half its original volume and is then diluted with 100 ml of water. The aqueous reaction mixture is extracted with ether and the ether extracts discarded. The aqueous solution is acidified, with cooling, with dilute hydrochloric acid to p~ 2 and then extracted with ethyl acetate (4 x 50 ml). The combined ethyl acetate extracts are dried over anhydrous magnesium sulfatel and then concentrated under reduced pressure to yield the desired product. It is purified by conversion to the cyclohexylamine salt, mp. 194-196, 25 ~44 (c=l~ in methanol).

HAl 62a-b The free acid is obtained by suspension of cyclohexylamine salt in 25 ml of ethyl acetate with 22 ml of N hydrochloric acid and extract-ing the aqueous layer with ~ x 35 ml of ethyl acetate.
The combined ethyl acetate extracts are dried over anhydrous magnesium sulfate and the solvent concen-trated under reduced pressure to yield the desired trans -l-carbobenzyloxy-4-fluoro-L proline.
B) Trans-4-fluoro-L-proline, hydrobromide A mixture of 3 grams of trans-1-carbobenzyloxy-4-fluoro-L-proline and 15 ml of hydrogen bromide in acetic acid (30-32%) is stirred for 1 hour, and then 150 ml of anhydrous ether is added. The solvent is decanted from the precipitate that is then tri-turated with fresh ether and finally with methyl ethyl ketone. The trans-4-fluoro-L-proline hydrobromide melts at 162-164 (dec), [al25 -30 (c=1% in methanol).
C) Trans-l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4-fluoro-L-proline To a stirred solution of 1.9 grams of trans 4-fluoro-L-proline hydrobromide in 25 ml of cold water there is added 1 gram of sodium carbonate to adjust pH to 8.2. Then with continued cooling (5) and stirring there is added dropwise 1.8 grams of D-3-acetylthio-2-methylpropionyl chloride in 2.5 ml of ether, while maintaining the pH at about 8.2-8.3 by the dropwise addition of a 25% aqueous sodium carbonate solution. The stirring and cooling is continued for one hour after the addition is completed. The reaction mixture is extracted with ethyl acetate (2 x 25 ml) and the extracts discarded. To the aqueous layer is added 50 ml of ethyl acetate and with stirring and , ~ HA162a-b cooling, concentrated hydrochloric acid is added dropwise to a pH of 2Ø The a~ueous layer is satu-rated with sodium chloride and the ethyl acetate layer separated. The aqueous layer is extracted with additional ethyl acetate (3 x 25 ml), the combined ethyl acetate extracts dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired product. The dicyclohexylamine salt is prepared by dissolving the product in 25 ml of ethyl acetate and adding a solution of 1.8 gram of dicyclo-hexylamine in 35 ml of ethyl acetate. The precipitated salt is filtered and recrystallized from isopropanol to yield the dicyclohexylamine salt of trans l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4-fluoro-L-proline;
15 mp. 209-211, E~]D5 -85 (c=1% methanol).
The free acid is recovered by dissolving the dicyclohexylamine salt in 5% aqueous potassium acid sulfate and extraction with ethyl acetate. The ethyl acetate solution is dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired trans l-[D-3-(acetylthio)-2-methyl-l-oxopropyl]-4-fluoro-L-proline.
Example 43 trans-4-fluoro-1-(D-3-mercapto-2-methyl-1-oxopropyl)-L-proline Argon is passed through a cold solution of 4.2 ml of concentrated ammonium hydroxide in 16 ml of water.
To this solution there is added, with stirring in an atmosphere of argon, 1.8 grams of trans-1-[D-3-(acetyl-thio)-2-methyl-1-oxopropyl]4-fluoro-L-proline. The reaction mixture is stirred for an additional two hours and is then extracted with ethyl acetate which is ~iA162a-b discarded. The aqueous layer is stirred, 30 ml of ethyl acetate added, and the aqueous layer acidified with concentrated hydrochloric acid. The aqueous layer is saturated with sodium chloride and the ethyl acetate layer separated. The aqueous layer is extracted with ethyl acetate (3 x 30 ml). The combined ethyl acetate extracts are dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired trans-4-fluoro-1-[D-3-mercapto-2-methyl-1-oxopropyl)-L-proline; [a]26 -112(c=1% in methanol).
Example 44 l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4,4-difluoro-L-proline A) l-carbobenzyloxy-4,4-difluoro-L-proline, methyl ester To a cooled stirred solution of 3.3 grams of 1-carbobenzyloxy-4-keto-L-proline, methyl ester in 80 ml of methylene dichloride there is added dropwise 3.3 ml diethylaminosulfurtrifluorids. The reaction mixture is allowed to remain overnight at room temperature. About 100 grams of crushed ice is added with stirring and the reaction mixture stirred for 45 minutes. The organic layer is separated and the aqueous layer extracted with methylene chloride (2 x 40 ml). The combined extracts are dried over anhydrous magnesium sulfate and then concentrated under reduced pressure to yield the desired l-carbo-benzyloxy-4,4-difluoro-L-proline, methyl ester.

'`

ilZ~Z3 ~A162a-b B) l-carbobenzyloxy-4,4-difluoro-L-proline A solution of 5.6 grams of 1-carbobenzyloxy-4,4-difluoro-L-proline, methyl ester in 50 ml of methanol is treated dropwise with 11.5 ml of 2 .I sodium hydrox-ide solution at 0-5. The reaction mixture is left at 0 for 1 hour and is then allowed to warm to room temperature overnight. The reaction mixture i5 con-centrated under reduced pressure to about one-half its original volume and is then diluted with 100 ml of water. The aqueous reaction mixture is extracted with ether and the ether extracts discarded. The aqueous solution is acidified with cooling with dilute hydrochloric acid to pll 2 and is then extracted with ethyl acetate (3 x 50 ml). The ethyl acetate ex-tracts are combined and washed with saturated sodium chloride solution, dried over anhydrous magnesium sulfate and concentrated to yield the desired product, l-carbobenzyloxy-4,4-difluoro-L-proline.
It is purified by conversion to the cyclohexylamine salt. mp. 180-185L~]D6 = -24 (c=1% in ethanol).
The free acid is obtained by treating an aqueous solution of the cyclohexylamine salt with hydrochloric acid and extracting the mixture with ethyl acetate (4 x 30 ml). The ethyl acetate extracts are dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired l-carbo-benzyloxy-4,4-difluoro-L-proline.
C) 4,4-Difluoro~L-proline, hydrobromide A mixture of 2.4 grams of 1-carbobenzyloxy-4,4-difluoro-L-proline and 12 ml of hydrogen bromlde in acetic acid (30-32%) is stirred for 30 minutes at room ~ . , ~ 23 HA162a-b temperature and then 300 ml of anhydrous ethe~ is added. The mixture is cooled and the precipitated solid is filtered and dried under reduced pressure.
The desired 4,4--difluoro-L-proline, hydrobromide melts at 163-165 (dec); [~D = -14 (c=l~ in methanol).
D) l-LD-3-(acetylthio)-2-methyl-1-oxopropyl]-4,4-difluoro-L-proline To a stirred solution of 2.7 grams of 4,4-difluoro-L-proline, hydrobromide in 30 ml of water, cooled to 5, there is added solid carbonate to adjust the pH
to 8.4. Then with continued cooling and stirring there is added dropwise 2.4 grams of D-3-acetylthio-2-methylpropionyl chloride in 3 ml of anhydrous ether, while maintaining the pII of the solution at 8.1-8.3 by the addition of a 25% aqueous sodium carbonate solution: The stirring and cooling is continued for one hour after the addition is completed. The reaction mixture is extracted with ethyl acetate (2 x 25 ml) and the extracts discarded. To the aqueous layer is added 50 ml of ethyl acetate and, with stirring and cooling, there is added dropwise concentrated hydro-chloric acid to a pH of 2Ø The aqueous layer is saturated with sodium chloride and the ethyl acetate layer separated. The aqueous layer is extracted with ethyl acetate (3 x 25 ml) and the combined ethyl acetate extracts dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired product. The dicyclohexylamine salt is prepared by dissolving the product in 40 ml of ethyl acetate and adding a solution of 2.3 grams of di-cyclohexylamine in 5 ml of ethyl acetate. The pre-:

.

l~X~ ~(Z3 ~1~162a-b cipitated salt is filtered and recrystallized from ethanol. The dicyclohexylamine salt of l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]4,4-difluoro-L-proline melts at ~25-227; L~]D = -70 (c=0.5% in methanol).
The free acid is recovered by dissolving the dicyclohexylamine salt in 5% aqueous potassium acid sulfate and extraction with ethyl acetate. The ethyl acetate solution is dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4,4-difluoro-L-proline.
Example 45 4,4-Difluoro-l-(D-3-mercapto-2-metnyl-1-oxopropyl)-L-proline Argon is passed through a cold solution of 4.6 ml of concentrated ammonium hydroxide in 11 ml of water.
To this solution there is added, with stirring in an atmosphere of argon 2.1 grams of 1-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-4,4-difluoro-L-proline. The reaction mixture is stirred an additional two hours and is then extracted with ethyl acetate, which is discarded.
The aqueous layer is stirred, 30 ml of ethyl acetate is added and the aqueous layer acidified with concentrated hydrochloric acid. The aqueous layer is saturated with sodium chloride and the ethyl acetate layer separated. The aqueous layer is extracted with ethyl acetate (3 x 25 ml). The combined ethyl acetate extracts are dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired 4,4-difluoro-1-(D-3-mercapto-2-methyl-1-oxopropyl)-L-proline.

~z~3 HA162a-b xample 46 l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-5-fluoro-2-pipecolic acid A~ l-Carbobenzyloxy-5-hydroxy-L-pipecolic acid, methyl ester A solution of 5 grams of 1-carbobenzyloxy-5-hydroxy-L-pipecolic acid in 60 ml of dioxane is treated with an ethereal solution of diazomethane portionwise, uniil the yellow color persists. The temperature is maintained at about 5 during the addition. The excess diazomethane is destroyed with glacial acetie acid and the resulting solution dried over anhydrous magnesium sulfate. The solution is concentrated under reduced pressure to yield the desired 1-carbobenzyloxy-5-hydroxy-L-pipecolic acid, methyl ester as a pale yellow viseous oil.
B) l-Carbobenzyloxy-5-tosyloxy-L-pipecolie aeid, methyl ester To a stirred solution of 5.7 grams of l-earbo-benzyloxy-5-hydroxy-L-pipeeolic acid, methyl ester in 12 ml of pyridine, there is added dropwise at 5 to 8 a solution of 4 grams of tosyl chloride in 6 ml of pyridine. The reaction mixture is kept at 5 for 72 hours and is then treated, with cooling, with 200 ml of ice-cold 2-N hydrochloric acid. The precipitate is dissolved in chloroform and the aqueous solution ex-traeted with additional chloroform (3 x 75 ml). The combined chloroform solutions are dried over anhydrous magnesium sulfate and coneentrated under reduced pressure to yield the desired 1-earbobenzyloxy-5-tosyloxy-L-pipeeolic aeid, methyl ester, melting at 74-76, after erystallization from isopropanol, La] 26 = _5, c=1%

~;Z4~23 HA162a-b in methanol, [(~26= -llC~, c=l'~ in chloroform.
C) l-Carbobenzyloxy-5-fluoro-L-pipecolic acid, methyl ester A stlrred suspension of 5.2 ~rams of l-carbo-benzyloxy-5-tosyloxy-L-pipecolic acid, methyl ester in 50 ml of diethylene ~lycol is treated with 5.2 grams of anhydrous potassium fluoride and the mixture heated at 80, with stirring for 14 hours. The cooled solution is diluted with 50 ml of water and extracted with ethyl acetate (3 x 100 ml). The ethyl acetate extracts are combined, washed with a saturated sodium chloride solution and dried over anhydrous maynesium sulfate. The solvent is removed under reduced pressure to yield the desired l-carbobenzyloxy-5-fluoro-L-pipecolic acid, methyl ester as a yellow oil.D) l-Carbobenzyloxy-5-fluoro-L-pipecolic acid To a cooled (0) solution of 4.6 grams of 1-carbobenzyloxy-5-fluoro-L-pipecolic acid, methyl ester in 32 ml of methanol there is added 7.3 ml of 2N
sodium hydroxide solution. The reaction mixture is ; allowed to remain at 0-5 for one hour and at room temperature overnight. The solution was concentrated to about one-half its volume under reduced pressure and diluted with 20 ml of water. The solution is extracted with ether, which is discarded. The aqueous solution is cooled, acidified with concentrated hydrochloric acid and extracted with ethyl acetate (3 x 50 ml). The combined ethyl acetate extracts are dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield the desired 1-carbobenzyloxy-5-fluoro-L-pipecolic acid. It is purified by conversion to the -~7 2 3 HA162a-b cyclohexylamine salt, which melts at 158-161 L~]D6 =
-11 (c=1% in methanol.
The free acid is obtained by treating an aqueous solution of the salt with hydrochloric acid, extracting the mixture with ethyl acetate (4 x 25 ml) and concen-trating the dried extracts under reduced pressure.
E) 5-Fluoro-L-pipecolic acid hydrobromide A mixture of 2.2 grams of 1-carbobenzyloxy-5-fluoro-L-pipecolic acid and 12 ml of hydrogen bromide 10 in acetic acid (30-32%) is stirred for 30 minutes at room temperature and then 300 ml of anhydrous ether is added. The cooled mixture is filtered and the pre-cipitated solid dried under reduced pressure to yield 5-fluoro-L-pipecolic acid hydrobromide.
F) l-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-5-fluoro-L-pipecolic acid To a suspension of 5.1 grams of 5-fluoro-L-pipecolic acid hydrobromide in 100 ml of dimethylacetonide there is added 10 grams of i~ methylmorpholine. To this mixture there is then added, slowly, with vigorous stirring 5.4 grams of D-3-acetyl-2-methylpropionyl chloride and the reaction mixture heated at 90 for three hours. The cooled reaction mixture is filtered and concentrated under reduced pressure. The residue is treated with dilute hydrochloric acid and is ex-tracted with ethyl acetate (3 x 150 ml). The ethyl acetate extracts are dried and then concentrated under reduced pressure to yield l-[D-3-(acetylthio)-2-methyl-l-oxopropyl]-5-fluoro-L-pipecolic acid.
The acid is purified by conversion to the dicyclo-hexylamine salt followed by crystalli3ation of the salt from acetonitrile.

l~Z~723 HA162a-b EYample 47 uoro-1-(D-3-mercapto-2-methyl-1-oxopropyl)-L-pipecolic acid ~Jitrogen is bubbled through a solution (5) of S 11 ml of concentrated ammonium hydroxide in 25 ml of water for 30 minutes. To this solution there is added 1.6 grams of 1-[D-3-(acetylthio)-2-methyl-1-oxopropyl]-5-fluoro-L-pipecolic acid and the mixture stirred Eor 15 minutes at 5 and then 4 hours at room temperature.
The solution is then cooled, acidified with concentrated hydrochloric acid and extracted with ethyl acetate (3 x 50 ml). The ethyl acetate extracts are dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield 5-fluoro-1-(D-3-mercapto-2-S methyl-l-oxopropyl)-L-pipecolic acid.
Example 48 1-(3-Mercapto-2-trifluoromethylpropanoyl)-L-pipecolic acid By substituting L-pipecolic acid tert-butyl ester for the L-proline tert-butyl ester in the procedure of Example 2, and submitting the product to the pro-cedures of Examples 3 and 4, 1-(3-mercapto-2-trifluoro-methylpropanoyl-L-pipecolic acid is obtained.
Example 49 1-(2-Mercapto-3,3,3-trifluoropropanoyl)-L-pipecolic acid By substituting L-pipecolic acid or the L-proline inthe procedure of Example 7, and then sub-mitting the product to the procedure of Example 8, 1-(2-mercapto-3,3,3-trifluoropropanoyl)-L-pipecolic acid is obtained.

llA162a-b Example 50 1-(3-Mercapto-2-trifluoromethylpropanoyl)-5,5-difluoro-DL-pipecolic acid By substituting 5,5-difluoro-DL-pipecolic acid [obtained from 5-keto-DL-pipecolic acid by the procedure described in J. Med. Chem. 20, 1176 (1977)]
for the 4,4-difluoro-L-proline in the procedure of Example 11 and submitting the product to the procedure of Example 12, 1-(3-mercapto-2-trifluoro-methylpropanoyl)-5,5-difluoro-DL-pipecolic acid is obtained.
Example 51 1,1'-[Dithiobis-(2-trifluorometh~1-3-propanoyl)~bis-5,5-difluoro-DL-pipecolic acid By substituting 1-(3-mercapto-2-trifluoro-methylpropanoyl)-5,5-difluoro-DL-pipecolic acid for the l-~3-mercapto-2-trifluoromethylpropanoyl)-L-proline in the procedure of Example 9, l,l'-[dithio-bis-(2-trifluoromethyl-3-propanoyl)]bis-5,5-difluoro-DL-pipecolic acid is obtained.
Example 52 1-(3-Mercapto-4,4,4-trifluorobutanoyl)-L-pipecolic acid By substituting L-pipecolic acid tert.-butyl ester for the L-proline tert.-butyl ester in the procedure of Example 14, and then submitting the product to the procedure of Example 15, 1-(3-mer-capto-4,4,4-trifluorobutanoyl)-L-pipecolic acid is obtained.
;

1~24723 HA162a-b ~xample 53 1-(3-Mercapto-2-trifluoromethylpropanoyl)-5,5-dichloro-DL-pipecolic acid By substituting 5,5-dichloro-DL-pipecolic acid [prepared from 5-keto-DL-pipecolic acid and phos-phorus pentachloride by a procedure similar to that described in J. Med. Chem. 20, 1176 (1977)] for the 4,4-difluor~Lproline in the procedure of Example 11 and then submitting the product to the procedure of Example 12, 1-(3-mercapto-2-trifluoromethylpropanoyl)-5,5-dichloro-DL-pipecolic acid is obtained.
Example 54 1-(3-Mercapto-2-methylpropanoyl)-5,5-difluoro-DL-pipecolic acid By substituting 3-acetylthio-2-methylpropanoic acid chloride for the 3-acetylthio-2-trifluoromethyl-propanoic acid chloride in the procedure of Example 11 and then submitting the product to the procedure of Example 12, 1-(3-mercapto-2-methylpropanoyl)-5,5-0 difluoro-DL-pipecolic acid is obtained.
Example 55 1-(3-Mercapto-2-methylpropanoyl)-5-fluoro-DL-pipecolic acid By substituting 3-acetylthio-2-methylpropanoic acid chloride for the 3-acetylthio-2-trifluoromethyl-propanoic acid chloride and 5-fluoro-DL-pipecolic acid [prepared from 5-hydroxypipecolic acid by a procedure similar to that descrbied in Biochemistry, 4, 2507 (1965)] for the 4,4-difluoro-L-proline in the procedure of Example 11, and then submitting the product to the procedure of Example 12, 1-(3-acetyl-thio-2-methylpropanoyl)-5-fluoro-DL-pipecolic acid 1~472:~
HA162a-b and l-(3-mercapto-2-methylpropanoyl)-5-fluoro-DL-pipecolic acid are obtained.
Example 56 1-(3-Mercaptopropanoyl)-5-bromo-DL-pipecolic acid Bysubstituting 3-acetylthiopropanoyl chloride for the 3-acetylthio-2-trifluoromethylpropanoic acid chloride and 5-bromo-DL-pipecolic acid [prepared from 5-hydroxypipecolic acid by a procedure similar to that described in Aust. J. Chem., 20, 1493 (1967)]
for 4,4-difluoro-L-proline in the procedure of Example 11 and submitting the product to the procedure of Example 12, 1-(3-acetylthiopropanoyl)-5-bromo-DL-pipecolic acid and l-(3-mercaptopropanoyl)-5-bromo-DL-pipecolic acid are obtained.
Example 57 1-(3-Acetylthio-2-trifluoromethylpropanoyl)-DL-pipe-colic acid methyl ester By substituting DL-pipecolic acid methyl ester for the L-proline tert-butyl ester in the procedure of Example 2, 1-(3-acetylthio-2-trifluoromethylpro-panoyl)-DL-pipecolic acid methyl ester is obtained.
Example 58 1-(3-Mercapto-2-trifluoromethylpropanoyl-DL-pipecolic acid methyl ester By substituting DL-pipecolic acid methyl ester for the L-proline tert-butyl ester and 3-mercapto-2-trifluoromethyl propanoic acid for the 3-acetylthio-2-methylpropanoic acid in the procedure of Example 2, , . _ ~247~3 ll~162a-b 1-(3-mercapto-2-trifluoromethylpropanoyl)-DL-pipeeolie aeid methyl ester is obtained.
Example 59 1-(3-Propanoylthio-2-trifluoromethylpropanoyl)-5-fluoro-DL-pipecolic acid , By substituting thiopropanoic aeid for the thiolaeetie acid in the procedure of Example 1, and then submitting the produet to the procedure of Example 26, 1-(3-propanoylthio-2-trifluoromethylpro-panoyl)-5-fluoro-DL-pipecolic acid is obtained.
Example 60 1-(3-Mereapto-2-methylpropanoyl)-5-fluoro-DL-pipecolie aeid sodium salt An aqueous solution of 1-(3-mercapto-2-methyl-propanoyl)-5-fluoro-DL-pipecolic acid is mixed with an equimolar amount of aqueous N-sodium hydroxide and the solution is freeze dried.
Example 61 1-(3-Mereaptopropanoyl)-5,5-diehloro-DL-pipecolic acid By substituting 3-acetylthiopropanoic aeid ehloride for the 3-aeetylthio-2-trifluoromethylpro-panoie aeid ehloride in the proeedure of Example 53, 1-(3-mercaptopropanoyl)-5,5-dichloro-DL-pipeeolie aeid is obtained.
The racemic forms of the final products in eaeh of the foregoing examples are produeed by util-izing the DL-form of the starting amino acid instead of the L-form.
Similarly, the D-form of the final products in eaeh of the foregoing examples is produeed by utilizing the D-form of the starting amino aeid instead of the L-form.

~723 HA162a-b ~ xample 62 1000 tablets each containing 100 mg. of l-(D-3-mercaptopropanoyl)-cis-4-fluoro-L-proline, are produced from the following ingredients:
1-(3-mercaptopropanoyl)-cis-4 fluoro-L-proline 100 g.
Corn starch 50 g.
Gelatin 7,5 g.
Avicel (microcrystalline cellulose) 25 g.
Magnesium stearate 2.5 g.
The l-(D-3-mercaptopropanoyl)-cis-4-fluor~-L-proline and corn starch are admixed 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 the granulation. This is then compressed in a tablet press to form 1000 tablets each containing 100 mg.
of active ingredient.
Example 63 1000 tablets each containing 200 mg. of 1-[D-3-(acetylthio)-2-methylpropanoyl]-cis-4-fluoro-L-proline are produced from the following ingredients:
1-[D-3-(acetylthio)-2-methylpro-panoyl]-cis-4-fluoro-L-proline200 g.
Lactose 100 g.
Avicel 150 g.
Corn starch 50 g.
Magnesium stearate 5 g.
The l-[D-3-(acetylthio)-2-methylpropanoyl]-cis-4-fluoro-L-proline, lactose and Avicel are admixed, then blended with the corn starch. Magnesium stearate is added. The dry mixture is compressed in a tablet press to form 1000 505 mg. tablets each containing 200 mg. of active ingredient. The tablets are l~Z~7~23 HA162~b coated with a solution of Methocel E 15 (methyl cellulose) including as a color a lake containing yellow #6~
Example 64 Two piece #l gelatin capsules each containing 250 mg. of 1-(3-mercapto-4,4,4-trifluorobutanoyl)-L-proline are filled with a mixture of the following ingredients:
1-(3-mercapto-4,4,4-trifluoro-butanoyl-L-proline 250 mg.
Magnesium stearate 7 mg.
USP lactose 193 mg.

Example 65 An injectable solution is produced as follows:
cis-l-[D-3-(mercapto)-2-methyl-propanoyl)]-cis-4-fluoro-L-proline 500 g Methyl paraben 5 g, Propyl paraben 1 g.
Sodium chloride 25 g.
Water for injection qs. 5 1.

The active substance, preservatives and sodium chloride are dissolved in 3 liters of water for injection and then the volume is brought up to 5 liters. The solution is filtered through a sterile filter and aseptically filled into pre-sterilized vials which are then closed with presterilized rubber closures. Each vial contains 5 ml. of solution in a concentration of 100 mg.

1124723 HA162a-b of active ingredient per ml. of solution for injection.
The products of each example can be similarly formulated as in Examples 62 to 65.

`:

Claims (20)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A process for preparing a compound of the formula or a basic salt thereof, wherein:
R is hydrogen, C2-C5 alkanoyl or methoxybenzyl;
m is 1 or 2;
n is 0 or 1;
R4 is hydrogen, C1-C4 alkyl or trifluoromethyl;
R3 is hydrogen, C1-C4 alkyl or trifluoromethyl and also halogen when n is 1;
R2 and R'2 are each independently hydrogen or halogen R6 is hydrogen and also halogen when m is 1;
R1 is hydrogen or C1-C4 alkyl;
with the proviso that at least one of R2 and R'2 must be halo-gen when R3 is hydrogen or C1-C4 alkyl, characterized by either a) reacting a compound of the formula with a compound of the formula or b) subjecting a compound of the formula wherein R is C2-C5 alkanoyl to basic hydrolysis or ammonoly-sis, to provide a compound of said formula wherein R is hydro-gen;
or c) treating a compound of the formula wherein R is methoxybenzyl with trifluoroacetic acid and mer-curic acetate, to provide a compound of said formula wherein R is hydrogen.

2. The process according to claim 1 wherein m is 1.

3. The process according to claim 1 wherein m is 1 and n is 1.

4. The process according to claim 1 wherein m is 1, n is 1 and R6 is hydrogen.

5. The process according to claim 1 wherein m is 1, n is 1, R6 is hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine.

6. The process according to claim 1 wherein m is 1, n is 1, R6 and R4 are hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine.

7. The process according to claim 1 wherein m is 1, n is 1, R3 is C1-C4 alkyl, R6 and R4 are hydrogen, R2 is hydro-gen or fluorine and R'2 is fluorine.

8. The process according to claim 1 wherein m is 1, n is 1, R3 is methyl or trifluoromethyl, R6 and R4 are hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine.

9. The process according to claim 1 wherein R3 is tri-fluoromethyl.

10. The process according to claim 1 wherein R6 is halogen and m is 1.

11. A compound of the formula or a basic salt thereof, wherein:
R is hydrogen, C2-C5 alkanoyl or methoxybenzyl;
m is 1 or 2;
n is 0 or 1;
R4 is hydrogen, C1-C4 alkyl or trifluoromethyl;
R3 is hydrogen, C1-C4 alkyl or trifluoromethyl and also halogen when n is 1;

R2 and R'2 are each independently hydrogen or halogen;
R6 is hydrogen and also halogen when m is 1;
R1 is hydrogen or C1-C4 alkyl;
with the proviso that at least one of R2 and R'2 must be halo-gen when R3 is hydrogen or C1-C4 alkyl, whenever prepared by the process of claim 1.

12. A compound as defined in claim 11 wherein m is 1, whenever prepared by the process of claim 2.

13. A compound as defined in claim 11 wherein m is 1 and n is 1, whenever prepared by the process of claim 3.

14. A compound as defined in claim 11 wherein m is 1, n is 1 and R6 is hydrogen, whenever prepared by the process of claim 4.

15. A compound as defined in claim 11 wherein m is 1, n is 1, R6 is hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine, whenever prepared by the process of claim 5.

16. A compound as defined in claim 11 wherein m is 1, n is 1, R6 and R4 are hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine, whenever prepared by the process of claim 6.

17. A compound as defined in claim 11 wherein m is 1, n is 1, R3 is C1-C4 alkyl, R6 and R4 are hydrogen, R2 is hydrogen or fluorine and R'2 is fluorine, whenever prepared by the process of claim 7.

18. A compound as defined in claim 11 wherein m is 1, n is 1, R3 is methyl or trifluoromethyl, R6 and R4 are hydro-gen, R2 is hydrogen or fluorine and R'2 is fluorine, whenever prepared by the process of claim 8.

19. A compound as defined in claim 11 wherein R3 is trifluoromethyl, whenever prepared by the process of claim 9.

20. A compound as defined in claim 11 wherein R6 is halogen and m is 1, whenever prepared by the process of claim 10.