Carboxyalkanoyl and hydroxycarbamoylalkanoyl derivatives of substituted prolines

Compounds, compositions and method of alleviating hypertension using a compound of the formula ##STR1## wherein R is hydrogen or lower alkyl; PA1 R.sub.1 is hydrogen, lower alkyl or phenyl-lower alkyl; PA1 R.sub.2 is hydrogen, lower alkyl or phenyl lower alkyl or halo substituted lower alkyl; PA1 R.sub.3 is hydroxy, --NHOH or lower alkoxy; PA1 Pr-COOR is a substituted proline of the structures ##STR2## R.sub.4 is halogen, keto, azido, cycloalkyl, phenyl, substituted phenyl, phenyl-lower alkyl, substituted phenyl-lower alkyl, ##STR3## or Y--R.sub.6 ; R.sub.5 is hydrogen or lower alkyl; PA1 Y is oxygen or sulfur; PA1 R.sub.6 is lower alkyl, phenyl, substituted phenyl, phenyl-lower alkyl, substituted phenyl-lower alkyl, 1- or 2-naphthyl, substituted 1- or 2- naphthyl, biphenyl, or substituted biphenyl; PA1 R.sub.7 is halogen or --Y--R.sub.8 ; PA1 R.sub.8 is lower alkyl, phenyl, phenyl-lower alkyl substituted phenyl-lower alkyl, biphenyl, napthyl, or the R.sub.8 groups join to complete an unsubstituted 5- or 6-membered ring or such ring wherein one or more carbon atoms are substituted by a lower alkyl or di(lower alkyl) group; PA1 R.sub.9 is keto, phenyl, 2- or 4-hydroxyphenyl; PA1 n is 0 or 1; and salts thereof.

BACKGROUND OF THE INVENTION 
Ondetti et al. in U.S. Pat. No. 4,105,776 discloses compounds of the 
formula 
##STR4## 
including those wherein the proline ring is substituted with a hydroxy or 
lower alkyl group as useful in reducing or relieving angiotensin related 
hypertension. 
Cushman et al. in U.S. Pat. No. 4,052,511 discloses compounds of the 
formula 
##STR5## 
including those wherein the proline ring is substituted with a hydroxy or 
lower alkyl group as being useful as angiotensin converting enzyme 
inhibitors. 
Ondetti et al. in U.S. Pat. No. 4,154,935 discloses compounds of the 
formula 
##STR6## 
wherein R.sub.2 and R.sub.2 ' are halogen or hydrogen as being useful as 
hypotensive agents. 
Iwao et al. in U.K. Patent Application, GB 2027025 A published Feb. 13, 
1980 disclose antihypertensive agents of the formula 
##STR7## 
wherein R.sub.1 is phenyl or hydroxy substituted phenyl. 
Ondetti et al. in U.K. Patent Application GB 2028327 A published Mar. 5, 
1980 disclose hypotensive agents of the general formula 
##STR8## 
wherein X is oxygen or sulfur and R.sub.1 is lower alkyl, phenyl, or 
phenyl-lower alkyl. 
Krapcho in U.S. Pat. No. 4,217,359 discloses compounds of the formula 
##STR9## 
wherein R.sub.0 and R.sub.1 can be hydrogen or lower alkyl. 
Krapcho in U.K. Patent Application GB 2,039,478 A and U.S. Ser. No. 99,164 
disclose mercaptoacyl derivatives of proline wherein the proline ring has 
a diether; dithioether, ketal or thioketal substituent in the 4-position. 
SUMMARY OF THE INVENTION 
The invention relates to new compounds which have the general formula 
##STR10## 
wherein R is hydrogen or lower alkyl. 
R.sub.1 is hydrogen, lower alkyl or phenyl-lower alkyl. 
R.sub.2 is hydrogen, lower alkyl, phenyl-lower alkyl or halo substituted 
lower alkyl. 
R.sub.3 is hydroxy, --NHOH or lower alkoxy. 
Pr--COOR is a substituted proline of the structures 
##STR11## 
R.sub.4 is halogen, keto, azido, cycloalkyl, phenyl, substituted phenyl, 
phenyl-lower alkyl, substituted phenyl-lower alkyl, 
##STR12## 
or Y--R.sub.6. 
R.sub.5 is hydrogen or lower alkyl. 
Y is oxygen or sulfur. 
R.sub.6 is lower alkyl, phenyl, substituted phenyl, phenyl-lower alkyl, 
substituted phenyl-lower alkyl, 1- or 2-naphthyl, substituted 1- or 
2-naphthyl, biphenyl, or substituted biphenyl. 
R.sub.7 is halogen or --Y--R.sub.8. 
R.sub.8 is lower alkyl, phenyl, phenyl-lower alkyl, substituted 
phenyl-lower alkyl, biphenyl, 1- or 2-naphthyl, substituted 1- or 
2-naphthyl, substituted biphenyl or the R.sub.8 groups join to complete an 
unsubstituted 5- or 6-membered ring or such ring wherein one or more 
carbon atoms are substituted by a lower alkyl or di(lower alkyl) group. 
R.sub.9 is keto, phenyl, 2- or 4-hydroxyphenyl. 
n is 0 or 1 and salts of the formula I compounds. 
The L in the above structures indicates a center of asymmetry which is in 
the L-configuration. 
DETAILED DESCRIPTION OF THE INVENTION 
The invention in its broadest aspect relates to carboxyalkanoyl (and esters 
thereof) and hydroxycarbamoylalkanoyl derivatives of proline 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 lower alkyl groups represented by any of the variables include straight 
and branched chain hydrocarbon radicals from methyl to heptyl, for 
example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, 
pentyl, isopentyl and the like. The C.sub.1 -C.sub.4 members and 
especially the C.sub.1 and C.sub.2 members, are preferred. 
The term lower alkoxy includes such lower alkyl groups bonded through an 
oxygen and the term lower alkylthio includes such lower alkyl groups 
bonded through a sulfur. 
The halogens are chlorine, bromine and fluorine; chlorine and fluorine 
being preferred. 
The term cycloalkyl refers to saturated rings of 3 to 7 carbon atoms with 
cyclohexyl being most preferred. 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, which is preferred, pentafluoroethyl, 
2,2,2-trichloroethyl, chloromethyl, bromomethyl, etc. 
The term phenyl-lower alkyl includes a phenyl ring attached to a lower 
alkyl group as defined above. Phenylmethyl and phenylethyl are preferred. 
The term substituted phenyl and substituted phenyl-lower alkyl include such 
groups wherein the phenyl ring has a lower alkyl, preferably methyl, lower 
alkoxy, preferably methoxy, lower alkylthio, preferably methylthio, Cl, 
Br, F, or hydroxy substituent. When the substituent is methyl, methoxy, Cl 
or F the phenyl ring may be di or trisubstituted. 
The compounds of formula I wherein R.sub.3 is lower alkoxy can be prepared 
by coupling an acid of the formula 
##STR13## 
with an imino acid of formula 
EQU Pr--COOR (III) 
(wherein Pr--COOR is as defined above, except that it is understood that 
the ring nitrogen of the free acid is bonded to hydrogen rather than to a 
carbon chain) by any of the methods known in the art for the preparation 
of amides. A preferred preparation provides a N-hydroxysuccinimido ester 
of the acid of formula II which can then be reacted with the imino acid of 
formula III to give the compound of formula IV: 
##STR14## 
where R.sub.3 is lower alkoxy and R.sub.1, R.sub.2 and Pr--COOR are as 
defined above. 
The compounds of formula I wherein R.sub.3 is --NHOH are prepared by 
reacting a compound of formula V: 
##STR15## 
wherein R.sub.3 is lower alkoxy with hydroxylamine. 
The compounds of formula I wherein R.sub.3 is hydroxy are formed by 
reaction of the formula I compound wherein R.sub.3 is alkoxy with NaOH. 
Various substituted prolines are disclosed by Mauger et al., Chem. Review, 
Vol. 66, p 47-86 (1966). Ondetti et al. disclose various alkyl, halogen, 
ether and thioether substituted prolines in U.S. Pat. Nos. 4,105,776, 
4,154,935 and U.K. Application 2,028,327. Iwao et al. in U.K. Application 
2,027,025 disclose various 5-substituted prolines. 
As disclosed by Krapcho in U.S. Pat. No. 4,217,359, the carbamoyloxy 
substituted prolines can be obtained by reacting the hydroxy substituted 
N-protected proline with phosgene and then the amine HN(R.sub.5).sub.2. 
R.sub.5 is as defined above. Removal of the N-protecting group yields the 
desired starting material. 
As disclosed by Krapcho in U.S. Ser. No. 99,164, the prolines of the 
formula 
##STR16## 
(wherein R and R.sub.8 are as defined above) can be prepared by reacting 
the keto compound of the formula 
##STR17## 
(wherein R is as defined above) with an alcohol or thiol having the 
formula 
EQU R.sub.8 --Y--H (VIII) 
(wherein R.sub.8 and Y are as defined above) 
in the presence of an orthoformate or thioformate of the formula 
HC(Y--R.sub.8).sub.3 and an acid such as concentrated sulfuric acid or 
p-toluenesulfonic acid. Removal of the carbobenzyloxy group by catalytic 
hydrogenation when Y is oxygen or by treatment with HBr and acetic acid 
when Y is sulfur yields the desired starting material. The spiro 
substituted prolines can be prepared in a similar manner by reacting the 
keto compound of formula VII with the alcohol or thio of the formula 
##STR18## 
wherein t is 2 or 3 and R.sub.12 and R.sub.13 are independently selected 
from hydrogen and lower alkyl. This reaction is performed in the presence 
of p-toluenesulfonic acid and removal of the carbobenzyloxy group yields 
the desired starting material. When either or both R.sub.12 and R.sub.13 
are lower alkyl it is preferred that the substituted proline of formula VI 
be treated directly with a molar excess of the alcohol or thiol of formula 
IX. 
As disclosed by Krapcho in U.S. Ser. No. 164,985 filed July 1, 1980 the 
4-substituted proline starting materials wherein the substituent R.sub.4 
is cycloalkyl, phenyl, substituted phenyl, phenyl-lower alkyl, or 
substituted phenyl-lower alkyl can be prepared by reacting the 4-keto 
proline of formula VII with a solution of the Grignard or lithium reagent 
EQU R.sub.4 --Mg--halo or R.sub.4 --Li (X) 
wherein halo is Br or Cl, to yield 
##STR19## 
This compound is treated with a dehydrating agent such as 
p-toluenesulfonic acid, sulfuric acid, potassium bisulfate, or 
trifluoroacetic acid to yield the 3,4-dehydro-4-substituted proline of the 
formula 
##STR20## 
Removal of the N-benzyloxycarbonyl protecting group and hydrogenation of 
the compound of formula XII yields the desired starting materials. The 
substituted proline wherein R.sub.4 is cyclohexyl can be prepared by 
further hydrogenation of the 4-phenyl proline compound. 
Preferred compounds of this invention with respect to the proline portion 
of the structure of formula I are those wherein: 
R.sub.4 is cyclohexyl, 
##STR21## 
or Y--R.sub.6 ; when Y is oxygen and 
R.sub.6 is lower alkyl of 1 to 4 carbons, 
##STR22## 
a substituted or unsubstituted 1- or 2-naphthyl of the formula 
##STR23## 
or a substituted or unsubstituted biphenyl of the formula 
##STR24## 
when y is sulfur and R.sub.6 is phenyl or substituted phenyl; p is zero, 
one or two; 
R.sub.14 is hydrogen, methyl, methoxy, methylthio, Cl, F, Br, or hydroxy; 
R.sub.7 is Cl, F, or --Y--R.sub.8 ; 
R.sub.8 is lower alkyl of 1 to 4 carbons or the R.sub.8 groups join to 
complete an unsubstituted 5- or 6-membered ring or said ring in which one 
or more of the carbons has a methyl or dimethyl substituent; 
R.sub.9 is phenyl, 2- or 4-hydroxyphenyl. 
Preferred carboxyalkanoyl (and esters thereof) and hydroxycarbamoylalkanoyl 
sidechain portions of the structure of formula I are those wherein: 
R.sub.2 is methyl, R.sub.1 is hydrogen and n is one. 
R.sub.2 is methyl, n is one, R.sub.1 is phenylethyl. 
The products of formula I wherein the proline ring is monosubstituted give 
rise to cis-trans isomerism. The configuration of the final product will 
depend upon the configuration of the R.sub.4 and R.sub.9 substituent in 
the starting material of formula III. In general, it is preferred that the 
R.sub.4 and R.sub.9 substituents be in the cis configuration. 
The compounds of this invention form 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, 
ammonium salts, aralkylamines like, dibenzylamine, 
N,N-dibenzylethylenediamine, lower alkylamines like methylamine, 
t-butylamine, procaine, lower alkylpiperidines like N-ethylpiperidine, 
cycloalkylamines, like cyclohexylamine or dicyclohexylamine, 1-adamantane, 
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 preferred. These 
and other salts which are not necessarily physiologically acceptable are 
useful in isolating or purifying 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 an 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 
neutralization techniques, e.g., with potassium bisulfate, hydrochloric 
acid, etc. 
The compounds of formula I including their pharmaceutically acceptable 
salts are useful as hypotensive agents. They inhibit the conversion of the 
decapeptide angiotensin I to angiotensin II and, therefore, are useful in 
relieving angiotensin related hypertension. The action of the enzyme renin 
on angiotensin, 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.fwdarw.(renin).fwdarw.angiotensin 
I.fwdarw.(ACE).fwdarw.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 angiotensin 
dependent hypertension in the species of mammal suffering therefrom is 
alleviated. A single dose, or preferably two to four divided daily doses, 
provided on a basis of about 0.1 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 substance is preferably 
administered orally, but parenteral routes such as the subcutaneous, 
intramuscular, intravenous or intraperitoneal routes can also be employed. 
The compounds of 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. chlorthiazide, 
hydrochlorothiazide, flumethiazide, hydroglumethiazide, 
bendroflumethiazide, methclothiazide, trichlorothiazide, polythiazide or 
benthiazide, as well as ethacrynic acid, ticrynafen, chlorthalidone, 
furosemide, musolimine, bumetanide, triamterene, amiloride and 
spironolactone, and salts of such compounds. 
The compounds of formula I can be formulated for use in the reduction of 
blood pressure 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 of mixture of compounds 
of formula I 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.

Illustrated process details are set forth in the following examples for the 
various reactions. These examples are preferred embodiments and also serve 
as models for the preparation of other compounds of this invention. The 
temperatures are given in degrees on the centigrade scale. 
EXAMPLE 1 
1-(3-Methoxycarbonyl-R-2-methylpropanoyl)-4,4-ethylene-dioxy-L-proline 
(a) 3-Methoxycarbonyl-2-methylpropionic acid hydroxysuccinimido ester 
A mixture of 3-methoxycarbonyl-2-methylpropanoic acid (14.6 g, 100 mmol) 
and N-hydroxysuccinimide (11.5 g, 100 mmol) in 200 ml 1,2-dimethoxyethane 
is cooled in an ice bath while stirring under argon. 
N,N'-Dicyclohexylcarbodiimide (22.2 g, 110 mmol) is added in several 
portions over a period of five minutes. The mixture is stirred cold for 
one hour and then at room temperature for two hours. The urea is removed 
by filtration and the filtrate is taken to dryness in vacuo leaving an oil 
and a small amount of solid. The oil is dissolved in a mixture of 
ether-ethyl acetate and filtered through Celite. Removal of the solvent 
gives 26.2 g yellow oil. This is chromatographed on 600 g Baker silica gel 
(the sample is preabsorbed from ethyl acetate). After elution of some fast 
moving material with ether-petroleum ether the desired 
N-hydroxysuccinimide (O-Su) ester is eluted with ether-petroleum ether 3:1 
to give 14.8 g (61%) of 3-methoxycarbonyl-2-methylpropionic acid 
hydroxysuccinimido ester. A small sample was obtained crystalline on 
trituration with cold ether, m.p. (s.45.degree.) 52.degree.-57.degree.. 
Anal. Calc'd. for C.sub.10 H.sub.13 O.sub.6 N: C, 49.38; H, 5.39; N, 5.76. 
Found: C, 49.37; H, 5.18; N, 5.70. 
(b) 1-(3-Methoxycarbonyl-R-2-methylpropanoyl)-4,4-ethylenedioxy-L-proline 
A mixture of 4,4-ethylenedioxy-L-proline (10.4 g, 60 mmol) [prepared as in 
Example 1A below] 2-methylbutanedioic acid, 
1-(2,5-dioxo-1-pyrrolidinyl)4-methyl ester (14.6 g, 60 mmol), 
triethylamine (16.8 ml, 12.1 g, 120 mmol) and 200 ml of dimethylformamide 
(DMF) are stirred under argon at room temperature for forty-two hours. The 
DMF is then removed in vacuo. The residue is dissolved in water and 
acidified with 10% KHSO.sub.4 solution. Sodium chloride is added and the 
product is extracted into ethyl acetate (4 extractions). The combined 
extracts are washed once with saturated NaCl solution, dried over 
MgSO.sub.4 and freed of solvent in vacuo leaving 19.6 g of a mixture of 
oil and solid. This is triturated with ethyl acetate to give 5.0 g (28%) 
of white solid m.p. (s. 145.degree.) 153.degree.-162.degree., 
[.alpha.].sub.D =60.8.degree. (c=1.26%, CHCl.sub.3). Recrystallization of 
1.5 g from 30 ml ethyl acetate gives 
1-(3-methoxycarbonyl-R-2-methylpropanoyl)-4,4-ethylenedioxy-L-proline 1.15 
g, m.p. 164.degree.-167.degree., [.alpha.].sub.D =-63.degree. (c=1.03%, 
CHCl.sub.3). 
Anal. Calc'd. for C.sub.13 H.sub.19 O.sub.7 N: C, 51.82; H, 6.36; N, 4.65. 
Found: C, 51.94; H, 6.49; N, 4.49 
In this and the following examples "s." is used as the abbreviation for 
sintering and "m.p." is used as the abbreviation for melting point. 
EXAMPLE 1A 
4,4-Ethylenedioxy-L-proline 
(a) N-Carbobenzyloxy-4-hydroxy-L-proline 
26.5 g (0.20 mole) of 4-hydroxy-L-proline and 32.8 ml. (0.23 mole) of 
benzyl chloroformate are reacted in 200 ml. of water and 100 ml of acetone 
in the 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-carbobenzyloxy-4-hydroxy-L-proline. This 
product is reacted with cyclohexylamine to form the cyclohexylamine salt 
yield 69 g, m.p. 193.degree.-195.degree.. The salt (34 g) is neutralized 
with N-hydrochloric acid to obtain 27 g of free acid as a colorless glass 
[.alpha.].sub.D.sup.26 -70.degree., (c, 1% in chloroform). 
(b) N-carbobenzyloxy-4-keto-L-proline 
21.5 g (0.81 mole) of N-carbobenzyloxy-4-hydroxy-L-proline is oxidized in 
1.2 liters of acetone with 83 ml of 8 N 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 approximately 300 ml 
before diluting with 1 liter of chloroform. The solution is washed with 
300 ml of saturated sodium chloride (four times), dried (MgSO.sub.4), 
filtered and the solvent evaporated to give 
N-carbobenzyloxy-4-keto-L-proline (22.8 g) which is crystallized from 
ether (50 ml)-hexane (150 ml) to obtain 17.2 g (81%) of product, m.p. 
99.degree.-101.degree., [.alpha.].sub.D.sup.26 +17.degree. (c, 1% in 
chloroform). 
(c) N-Carbobenzyloxy-4,4-ethylenedioxy-L-proline 
A stirred mixture of 12.8 g (0.049 mole) of 
N-carbobenzyloxy-4-keto-L-proline, 53 ml (0.095 mole) of ethylene glycol, 
and 0.35 g of p-toluenesulfonic acid H.sub.2 O in 1.31 l. of benzene is 
heated and the resulting solution is refluxed for 7 hours (water formed is 
collected in a Dean-Stark apparatus). After standing overnight at room 
temperature, the lower glycol layer is separated and the benzene solution 
is washed with 150 ml of saturated sodium chloride, dried (MgSO.sub.4), 
and the solvent evaporated to give 14.6 g of 
N-carbobenzyloxy-4,4-ethylenedioxy-L-proline as a syrupy residue. The 
latter is dissolved in 60 ml of ethanol, filtered, treated with 5 g of 
cyclohexylamine, and diluted with ether. On seeding and rubbing, the 
crystalline cyclohexylamine salt separates; weight after cooling 
overnight, 9.0 g., m.p. 179.degree.-180.degree. (s. 173.degree.). The 
material is recrystallized from acetonitrile, m.p. 182.degree.-184.degree. 
(s. 179.degree.), [.alpha.].sub.D.sup.26 -21.degree. (c, 1 % in EtOh). 
The cyclohexylamine salt (8.4 g) is suspended in 40 ml of ethyl acetate, 
stirred, cooled, and treated with 40 ml of 1 N hydrochloric acid. The 
layers are separated, the aqueous phase extracted with additional ethyl 
acetate (3.times.40 ml), the combined organic layers are dried 
(MgSO.sub.4), and the solvent evaporated, finally at 0.2 mm. The syrupy 
residue which begins to crystallize is rubbed under ether and the ether 
evaporated to give 6.4 g (42%) of nearly colorless 
N-carbobenzyloxy-4,4-ethylenedioxy-L-proline, m.p. 101.degree.-103.degree. 
(s. 98.degree.), [.alpha.].sub.D.sup.26 -34.degree. (c, 1% in CHCl.sub.3). 
(d) 4,4-Ethylenedioxy-L-proline 
A solution of 3.2 g (0.0104 mole) of 
N-carbobenzyloxy-4,4-ethylenedioxy-L-proline in 100 ml of methanol-water 
(2:1) is treated with 1 g of 5% palladium-carbon and shaken on the Parr 
hydrogenator for 6 hours. The catalyst is filtered off under nitrogen, 
washed with methanol, and the combined filtrates evaporated, finally at 
0.1-0.2 mm, to give 1.7 g (94%) of colorless solid, 
4,4-ethylenedioxy-L-proline; m.p. 245.degree.-247.degree. (dec.); 
[.alpha.].sub.D.sup.26 -32.degree. (c, 0.5% in 1:1 meOH--H.sub.2 O). 
EXAMPLE 2 
1-(3-Carboxy-R-2-methylpropanoyl)-4,4-ethylenedioxy-L-proline 
1-(3-methoxycarbonyl-R-2-methylpropanoyl)-4,4-ethylenedioxy-L-proline (3.0 
g, 10 mmol) obtained as in Example 1 is added to 25 ml cold 1 N NaOH. 
After stirring cold for three hours the solution is acidified with solid 
KHSO.sub.4. Six ethyl acetate extractions give 2.75 g of white solid. This 
is triturated with ethyl acetate-ether and 2.4 g (83%) of crystalline 
material is harvested by filtration. Recrystallization from ethyl acetate 
(150 ml) gives 
1-(3-carboxy-R-2-methylpropanoyl)-4,4-ethylenedioxy-L-proline, 1.9 g, m.p. 
155.degree.-158.degree., [.alpha.].sub.D =-26.4 (c=1.36%, absolute ethanol 
(EtOH). 
Anal. Calc'd. for C.sub.12 H.sub.17 O.sub.7 N: C, 50.17; H, 5.96; N, 4.88. 
Found: C, 50.39; H, 5.89; N, 4.66. 
EXAMPLE 3 
1-(3-Carboxy-2-methylpropanoyl)-4,4-ethylene dithio-L-proline R/S: 
92.5/7.5. 
(a) 1-(3-Methoxycarbonyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline 
A mixture of 4,4-ethylenedithio-L-proline, hydrobromide (11.2 g, 39 mmol) 
[made as in Example 3A] 3-methoxycarbonyl-2-methylpropionic acid 
hydroxysuccinimido ester [9.5 g, 29 mmol] made as in Example 1(a) above, 
and triethylamine (16.4 ml, 117 mmol) in 200 ml dimethylformamide (DMF) is 
stirred under argon at room temperature for eighteen hours. The 
dimethylformamide (DMF) is removed in vacuo. The residue is dissolved in 
water and acidified with 10% KHSO.sub.4 solution. Four extractions with 
ethyl acetate give a brown oil. This is chromatographed on 600 g Baker 
silica gel using 0.5% methanol in CHCl.sub.3 and 1% methanol in CHCl.sub.3 
to elute the product. A total of 11.1 g (85%) of material is obtained in 
several pools of fractions. The material appearing the cleanest by TLC 
weighed 3.5 g. On standing under ether crystalline material is deposited 
(1.6 g). Saponification of a small sample of this material followed by 
acid hydrolysis and ion exchange chromatography gives 
.alpha.-methylsuccinic acid which is largely (&gt;85%) the R isomer. 
Recrystallization of a small amount of this material gave an analytical 
sample of 
1-(3-methoxycarbonyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline. M.P. 
130.degree.-132.degree., [.alpha.].sub.D =-9.degree. (c=1.0, absolute 
ethanol). 
Anal. Calc'd. for C.sub.13 H.sub.19 O.sub.5 NS.sub.3 : C, 46.83; H, 5.74; 
N, 4.20; S, 19.23. Found: C, 46.90; H, 5.90; N, 4.09; S, 19.43. 
(b) 1-(3-Carboxy-2-methylpropanoyl)-4,4-ethylenedithio-L-proline 
The 1-(3-methoxycarbonyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline of 
part (a) (Example 3) 2.6 g, 7.8 mmol) is added to 20 ml cold 1 N NaOH. 
After stirring in an ice bath for three hours the solution is acidified 
with solid KHSO.sub.4 and through extraction with ethyl acetate gives 2.7 
g solid foam which fails to crystallize [.alpha.].sub.D =-10.6.degree. 
(c=1.27, absolute ethanol). A small sample of this foam (100 mg) is 
hydrolyzed at reflux for two hours with 2 ml 1 N HCl. After removal of the 
solvent in vacuo the residue is dissolved in water and run through a 
column packed with 10 ml Dowex 50WX2 (H.sup.+) resin to give 
.alpha.-methylsuccinic acid [.alpha.].sub.D =+11.7 (c=1.05, absolute 
ethanol) (literature rotation R isomer +15.5; S isomer -15.0). This sample 
is, therefore, .about.85% R isomer. 
The foam described above (2.25 g, 7.05 mmol) is dissolved in ethyl acetate 
(50 ml) and filtered to remove a small amount of insoluble material. To 
the filtrate is added cyclohexylamine (1.7 ml, 1.485 g, 15 mmol). The 
white solid that precipitated is harvested and recrystallized from 
isopropanol to give 1.7 g (47%) 
1-(3-carboxy-2-methylpropanoyl)-4,4-ethylenedithio-L-proline m.p. 
(180.degree.) 190.degree.-192.degree., [.alpha.].sub.D =-15.4.degree. 
(c=0.975, absolute ethanol). 
Anal. Calc'd. for C.sub.12 H.sub.17 O.sub.5 NS.sub.2 2 C.sub.6 H.sub.13 N: 
C, 55.68; H, 8.37; N, 8.12; S, 12.39. Found: C, 55.47; H, 8.47; H, 8.46; 
S, 12.65. 
The cyclohexylamine salt (1.7 g, 3.3 mmol) is dissolved in 10% KHSO.sub.4 
solution and the diacid is extracted into ethyl acetate, dried and freed 
of solvent in vacuo to give 1.0 g (95%) of white solid foam. 
[.alpha.].sub.D =-10.2.degree. (c=1.26, absolute ethanol). A small sample 
of this material is hydrolyzed as described above to give the 
.alpha.-methylsuccinic acid. [.alpha.].sub.D =+13.2.degree. (c=1.13, 
absolute ethanol). Therefore, this sample is about 92.5% R isomer. 
EXAMPLE 3A 
4,4-Ethylenedithio-L-proline hydrobromide 
(a) N-Carbobenzyloxy-4,4-ethylenedithio-L-proline, methyl ester 
A stirred solution of 3.9 g (0.014 mole) of 
N-carbobenzyloxy-4-keto-L-proline, methyl ester in 60 ml of methylene 
chloride is treated with 3 ml (0.036 mole) of ethanedithiol, cooled to 
8.degree., and treated under an argon blanket with 3 ml (0.024 mole) of 
boron trifluoride etherate. After removing the cooling bath, the pale 
yellow solution is stirred for an additional hour and kept overnight at 
room temperature. The solution is stirred, treated with several pieces of 
crushed ice, followed by 20 ml of water. After 30 minutes the layers are 
separated and the aqueous phase (50 ml) is extracted with additional 
methylene chloride (3.times.30 ml). The combined organic layers are washed 
with 50 ml of saturated sodium chloride solution, dried (MgSO.sub.4), and 
the solvent removed on a rotary evaporator to give 6 g (100%) of a pale 
yellow oil N-carbobenzyloxy-4,4-ethylenedithio-L-proline, methyl ester. 
(b) N-Carbobenzyloxy-4,4-ethylenedithio-L-proline 
The methyl ester product from part (a) (7.4 g, approximately 0.018 mole) is 
dissolved in 65 ml of methanol, treated dropwise at -1.degree. to 
4.degree. with 14.5 ml (0.029 mole) of 2 N sodium hydroxide, kept at 
0.degree. for one hour, and at room temperature overnight. After removing 
about half the solvent on a rotary evaporator, the solution is diluted 
with 125 ml of water, washed with ether (wash discarded), acidified while 
cooling with 5 ml of 1:1 hydrochloric acid to a pH of 2, and extracted 
with ethyl acetate (4.times.50 ml). The combined extracts are washed with 
50 ml. of saturated sodium chloride, dried (MgSO.sub.4), and the solvent 
evaporated to give 6 g of a pale yellow viscous oil. This oil is dissolved 
in 25 ml of ethanol, treated with 1.8 g of cyclohexylamine in 5 ml of 
ethanol, and diluted to 300 ml with ether. On seeding and rubbing, the 
crystalline cyclohexylamine salt separates to yield after overnight 
cooling 5.7 g of N-carbobenzyloxy-4,4-ethylenedithio-L-proline 
cyclohexylamine salt; m.p. 205.degree.-207.degree. (s. 201.degree.). 
Recrystallization from 50 ml of ethanol-400 ml ether yields 4.9 g of 
colorless solid salt; m.p. 207.degree.-209.degree. (s. 201.degree.), 
[.alpha.].sub.D.sup.25 -15.degree. (c, 1% in chloroform). 
The cyclohexylamine salt (4.8 g) is suspended in 25 ml of ethyl acetate, 
stirred, and treated with 25 ml of 1 N hydrochloric acid. When two clear 
layers are obtained, they are separated, the aqueous phase is extracted 
with additional ethyl acetate (3.times.25 ml), the combined organic layers 
are dried (MgSO.sub.4), and the solvent evaporated to give 3.8 g (62%) of 
N-carbobenzyloxy-4,4-ethylenedithio-L-proline as a pale yellow viscous 
syrup. 
(c) 4,4-Ethylenedithio-L-proline, hydrobromide 
N-Carbobenzyloxy-4,4-ethylenedithio-L-proline (3.7 g, 0.011 mole) is 
treated with 20 ml of hydrogen bromide in acetic acid (30-32%), stoppered 
loosely, and stirred magnetically. Mixing is difficult due to the 
viscosity of the starting material and the latter is broken up as much as 
possible with a spatula. In the meantime, the crystalline product begins 
to separate. Further quantities of hydrogen bromide in acetic acid are 
added after 15 minutes (10 ml) and after 25 minutes (5 ml) and stirring is 
continued for a total of 35 minutes. Ether (250 ml) is added to complete 
precipitation of the product and after cooling for 15 minutes the cream 
colored material is filtered under nitrogen, washed with ether, and dried 
in vacuo to give 2.7 g of 4,4-ethylenedithio-L-proline, hydrobromide; m.p. 
240.degree.-242.degree. (dec.); sintering and darkening from approximately 
200.degree.; [.alpha.].sub.D.sup.26 -40.degree. (c, 0.5% in 1:1 
chloroform-methanol). 
EXAMPLES 4-16 
Following the procedure of Examples 1 and 2 wherein the compound of Column 
I is treated to form the compound of column II which is then treated to 
form the product compound of Column III. 
______________________________________ 
Column I 
##STR25## 
Column II 
##STR26## 
Column III 
##STR27## 
Example 
n R.sub.3 R.sub.2 R.sub.1 
______________________________________ 
4 1 OC.sub.2 H.sub.5 
H 
##STR28## 
5 1 OCH.sub.3 H H 
6 1 OCH.sub.3 CH.sub.3 
##STR29## 
7 1 OCH.sub.3 C.sub.3 H.sub.7 
H 
8 2 OCH.sub.3 C.sub.2 H.sub.5 
H 
9 2 OCH.sub.3 CH.sub.3 
CH.sub.3 
10 2 OC.sub.2 H.sub.5 
CH.sub.3 
H 
11 1 OC.sub.2 H.sub.5 
C.sub.3 H.sub.7 
H 
12 1 OC.sub.2 H.sub.5 
C.sub.2 H.sub.5 
H 
13 1 OC.sub.3 H.sub.7 
CH.sub.3 
H 
14 3 OC.sub.3 H.sub.7 
CH.sub.3 
CH.sub.3 
15 1 OC.sub.3 H.sub.7 
C.sub.3 H.sub.7 
H 
16 1 OC.sub.3 H.sub.7 
C.sub.2 H.sub.5 
CH.sub.3 
______________________________________ 
EXAMPLE 17 
1-(3-Carboxylpropanoyl)-4,4-ethylenedithio-L-proline 
Following the procedure of Example 3 but substituting 
3-methoxycarbonylpropanoic acid hydroxysuccinimido ester for 
3-methoxycarbonyl-2-methylpropanoic acid hydroxysuccinimido ester then 
1-(3-carboxylpropanoyl)-4,4 ethylenedithio-L-proline is obtained. 
EXAMPLE 18 
1-(3-Carboxy-2,3-dimethylpropanoyl)-4,4-ethylenedithio-L-proline 
Following the procedure of Example 3 but substituting 
3-methoxycarbonyl-2,3-dimethylpropanoic acid hydroxysuccinimido ester for 
3-methoxycarbonyl-2-methylpropanoic acid hydroxysuccinimido ester then 
1-(3-carboxy-2,3-dimethylpropanoyl)-4,4 ethylenedithio-L-proline is 
formed. 
EXAMPLE 19 
1-(3-Ethoxycarbonyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline 
Following the procedure of Example 3 but substituting 
3-ethoxycarbonyl-2-methylpropanoic acid hydroxysuccinimido ester in place 
of 3-methoxycarbonyl-2-methylpropanoic acid hydroxysuccinimido ester then 
1-(3-ethoxycarbonyl-2-methylpropanoyl)-4,4 ethylene-dithio-L-proline is 
formed. 
EXAMPLE 20 
1-(3-Hydroxycarbamoyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline 
1-(3-ethoxycarbonyl-2-methylpropanoyl)-4,4-ethylenedithio-L-proline (2.4 g) 
is dissolved in absolute ethanol (8 ml). An ethanolic solution of 
hydroxylamine [prepared from hydroxylamine hydrochloride (0.7 g) and 
sodium ethylate] is added followed by a solution of sodium (0.23 g) in 
absolute ethanol (8 ml). After two hours the reaction mixture is added to 
vigorously stirred ether (500 ml). The precipitate is filtered and dried 
to obtain 1-(3-hydroxycarbamoyl-2-methylpropanoyl)-4,4 
ethylenedithio-L-proline, yield 2 g. The free acid is prepared by 
treatment with an ion exchange resin (Dowex 50 in the hydrogen form). 
EXAMPLE 21 
4-[(4-Chlorophenyl)methyl]-1-(3-methoxycarbonyl-2-methylpropanoyl-L-proline 
(a) [(4-Chlorophenyl)methyl]triphenylphosphonium chloride 
A stirred solution of 158 g, (0.6 mole) of triphenylphosphine in 800 ml of 
xylene is treated with 97 g of 4-chlorobenzyl chloride. The resulting 
solution is heated (product begins to crystallize at this point) and 
refluxed for six hours. After standing overnight at room temperature, the 
solid is filtered, washed with xylene and then with ethyl acetate, and 
dried in a desiccator to yield 161 g of colorless solid 
[(4-chlorophenyl)methyl]triphenylphosphonium chloride; m.p. 
283.degree.-285.degree.. 
(b) N-Carbobenzyloxy-4-[(4-chlorophenyl)methylene]-L-proline 
Interaction of 15.2 g (0.32 mole) of 50% sodium hydride (oil dispersion) 
with 300 ml of dimethylsulfoxide, followed by treatment with a suspension 
of 135 g (0.32 mole) of [(4-chlorophenyl)methyl]triphenylphosphonium 
chloride in 300 ml of dimethyl sulfoxide (warmed to 70.degree. and then 
cooled to 22.degree.) and then with a solution of 26.4 g (0.1 mole) of 
N-carbobenzyloxy-4-keto-L-proline in 80 ml of dimethylsulfoxide according 
to the procedure of Example 21A (a) gives 13 g of pale yellow product as a 
sticky foam. This material is dissolved in 30 ml of acetonitrile and 
treated with 6.5 g of dicyclohexylamine to yield 15.3 g of nearly 
colorless N-carbobenzyloxy-4-[(4-chlorophenyl)methylene]-L-proline, 
dicyclohexylamine salt; m.p. 180.degree.-182.degree. (s. 177.degree.); 
[.alpha.].sub.D.sup.25 +6.2.degree. (c, 1% in chloroform). 
Anal. Cal'd. for C.sub.20 H.sub.18 ClNO.sub.4.C.sub.12 H.sub.23 N: C, 
69.48; H, 7.47; N, 5.07; Cl, 6.41. Found: C, 69.14; H, 7.20; N, 5.03; Cl, 
6.23. 
The above dicyclohexylamine salt (7.5 g) is suspended in ethyl acetate and 
treated with 10% potassium bisulfate according to the procedure of Example 
21A(a) to give 5.3 g of sticky 
N-carbobenzyloxy-4-[(4-chlorophenyl)methylene]-L-proline. 
(c) cis-4-[(4-Chlorophenyl)methyl]-L-proline, hydrobromide 
A solution of 5.3 g (0.014 mole) of 
N-carbobenzyloxy-4-[(4-chlorophenyl)methylene]-L-proline in 150 ml of 
ethanol is treated with 0.45 g of platinum dioxide and shaken on a Parr 
hydrogenator at a starting pressure of 15 lbs. (bottle gauge). The uptake 
of hydrogen is carefully monitored and whenever the pressure falls to 5 
lbs the bottle is replenished with hydrogen to 15 lbs. A noticeable 
slowing down of the rate of hydrogen uptake is observed after eight 
minutes and the hydrogenation is interrupted after a total of ten minutes 
(21.5 lbs of hydrogen). The catalyst is filtered off (celite bed under 
nitrogen atmosphere), washed well with ethanol, and the combined filtrates 
are evaporated, finally at 0.2 mm, to yield 4.6 g of 
N-carbobenzyloxy-cis-4-[(4-chlorophenyl)methyl]-L-proline as a colorless 
brittle foam. 
This material (4.5 g, 0.012 mole) is treated with 25 ml of hydrogen bromide 
in acetic acid (30-32%), stoppered loosely, and stirred magnetically. 
After 30 minutes the yellow-orange mixture (some crystalline product 
separates) is diluted to 500 ml with ether to complete precipitation and 
stirred with cooling for 30 minutes. The light pink product is filtered 
under nitrogen, washed with ether, and dried in vacuo to yield 3.3 g of 
cis-4-[(4-chlorophenyl)methyl]-L-proline, hydrobromide; m.p. 
233.degree.-235.degree. (dec., preceded by gradual darkening and 
sintering); [.alpha.].sub.D.sup.25 +1.5.degree.. (c, 1% in methanol). 
Anal. Calc'd. for C.sub.12 H.sub.14 ClNO.sub.2.HBr: C, 44.95; H, 4.72; N, 
4.37; Br, 24.92. Found: C, 45.03; H, 4.72; N, 4.38; Br, 24.65. 
(d) 
4-[(4-Chlorophenyl)methyl]-1-(3-methoxycarbonyl-2-methylpropanoyl)-L-proli 
ne 
Following the procedure of Example 3 but substituting 
cis-4-[(4-chlorophenyl)methyl]-L-proline hydrobromide from step (c) above, 
in place of 4,4-ethylenedi thio-L-proline hydrobromide then 
4-[(4-chlorophenyl)methyl]-1-(3-methoxycarbonyl-2-methylpropanoyl)-L-proli 
ne is formed. 
EXAMPLE 21A 
(a) N-Carbobenzyloxy-4-(phenylmethylene)-L-proline 
To a 1 liter flask are added 7.6 g (0.16 mole) of sodium hydride (50% 
suspension) and 150 ml of dry dimethylsulfoxide. The suspension is stirred 
and then maintained at 70.degree. for thirty minutes (all of the sodium 
hydride has reacted at this point). The solution is cooled to 30.degree. 
and treated portionwise with a suspension of 61.1 g (0.16 mole) of 
benzyltriphenylphosphonium chloride (dried in vacuo overnight) in 150 ml 
dimethylsulfoxide and the resulting intense red suspension is heated to 
70.degree.. This mixture is cooled to 25.degree. and treated with a 
solution of 13.2 g (0.05 mole) of N-carbobenzyloxy-4-keto-L-proline in 40 
ml of dimethylsulfoxide over a period of twenty minutes. This mixture is 
maintained at 65.degree.-70.degree. for four hours, allowed to stand 
overnight at room temperature, and then poured onto a solution of 10 g of 
potassium bicarbonate in 400 ml of icewater. Some ice is added to the 
mixture to bring the volume to 1 liter and it is then extracted three 
times with 250 ml portions of ether. The ether phases are discarded and 
the aqueous phase is cooled and acidified with 50 ml of 6 N hydrochloric 
acid. The product is extracted with 250 ml of chloroform and then twice 
with 100 ml of chloroform. The organic phases are combined, dried 
(MgSO.sub.4), filtered and the solvent evaporated to give 102 g of pale 
brown viscous residue. The latter is triturated with 500 ml of ether. The 
ether is decanted from the brown residue (mostly triphenylphosphineoxide) 
and the latter is triturated twice with 100 ml of ether. The ether phases 
are combined, cooled and treated portionwise with a solution of 10 g of 
sodium bicarbonate in 200 ml of water. The layers are separated and the 
organic phase is extracted with 10 ml of water. The ether phase is 
discarded and the aqueous phases are combined, cooled, acidified with 18 
ml of 6 N hydrochloric acid and extracted three times with 100 ml of 
ether. The organic layers are combined, dried (MgSO.sub.4), filtered and 
the solvent evaporated to give 8.9 g (52.6%) of a pale yellow foam. The 
bulk of this compound 8.6 g) is dissolved in 20 ml of acetonitrile and 
treated with 4.6 g of dicyclohexylamine. The product slowly crystallizes. 
After standing overnight in the cold, the nearly colorless 
dicyclohexylamine salt is filtered and dried to yield 11.0 g of 
N-carbobenzyloxy-4-(phenylmethylene)-L-proline, dicyclohexylamine; m.p. 
142.degree.-150.degree.. After recrystallization from 65 ml of 
acetonitrile, 9.5 g of nearly colorless dicyclohexylamine salt are 
obtained; m.p. 150.degree.-155.degree.; [ .alpha.].sub.D.sup.25 
+7.7.degree. (c, 1% in chloroform). 
Anal. Calc'd. for C.sub.20 H.sub.19 NO.sub.4.C.sub.12 H.sub.23 N: C, 74.09; 
H, 8.16; N, 5.40. Found: C, 73.87; H, 8.18; N, 5.33. 
This dicyclohexylamine salt (9.4 g) is suspended in 100 ml of ethyl acetate 
and treated with 100 ml of 10% potassium bisulfate. The mixture is shaken 
and the aqueous phase is extracted twice with 50 ml of ethyl acetate. The 
organic phases are combined, dried (MgSO.sub.4) filtered and the solvent 
evaporated to give 6.4 g (38%) of pale yellow foam-like solid 
N-carbobenzyloxy-4-(phenylmethylene)-L-proline; [.alpha.].sub.D.sup.25 
-2.5.degree. (c, 1% in chloroform); R.sub.f 0.29 (85:15 toluene:acetic 
acid on silica gel). 
Treatment of this material according to the procedures of Example 21 (c) 
and (d) yields the corresponding 4-(phenylmethyl)-L-proline product. 
EXAMPLE 22 
1-(3-Methoxycarbonyl-2R-methylpropanoyl)-4-S-phenylthio-L-proline 
(a) 3-Methoxycarbonyl-2-R-methylpropionic acid 
(RS)-3-Methoxycarbonyl-2-methylpropionic acid (36.8 g) is dissolved in 
ether (200 ml) and mixed with dehydroabietylamine (91.3 g) dissolved in 
400 ml of ether. After storing the mixture for one hour at room 
temperature the crystals are filtered and recrystallized from ethyl 
acetate, to yield 25.2 g of 3-methoxycarbonyl-2-R-methylpropionic acid 
m.p. (173.degree.) 144.degree.-146.degree. C. [.alpha.].sup.22 
=+30.5.degree. (c=1.5, EtOH). 
(b) 1-(3-Methoxycarbonyl-2R-methylpropanoyl)-4-S-phenylthio-L-proline 
3-Methoxycarbonyl-2-R-methylpropionic acid (2 g, 13.75 mmoles) and 
N-hydroxybenzotriazole (1.91 g, 12.5 mmoles) are dissolved in 
tetrahydrofuran (36 ml) and to this solution, chilled in an ice bath, 
dicyclohexylcarbodiimide (2.57 g, 12.5 mmoles) is added. After two hours 
stirring at room temperature the precipitate is filtered off and the 
filtrate is dissolved in N,N-dimethylformamide, then (36 ml) 
cis-4-phenylthio-L-proline (3.8 g, 12.5 mmoles) and triethylamine (3.5 ml) 
are added. The reaction is allowed to proceed for eighteen hours at room 
temperature, the solvent is removed in vacuo, the residue is dissolved in 
ethyl acetate and washed with 0.1 N, HCl, saturated aqueous sodium 
chloride, dried (MgSO.sub.4) and concentrated to dryness. The residue is 
then taken into ethyl acetate, the crystals are filtered off and the 
filtrate concentrated to dryness and chromatographed on a column of silica 
gel with benzene:acetic acid (8:2). The fractions containing the desired 
product are concentrated to dryness, reevaporated from water 
(freeze-drying) and crystallized from ethyl acetate-hexane to yield 3.3 g 
of 1-(3-methoxycarbonyl-2-R-methylpropanoyl)-4-S-phenylthio-L-proline m.p. 
(88.degree.) 94.degree.-96.degree.. 
EXAMPLE 23 
1-(4-Methoxycarbonyl-2R-methylbutanoyl)-4-S-phenylthio-L-proline 
(a) 4-Methoxycarbonyl-2-R-methylbutyric acid 
Substituting 4-methoxycarbonyl-2-methylbutyric acid for 
3-R-methoxycarbonyl-2-methylpropionic acid while following the procedure 
of Example 22(a), then 4-methoxycarbonyl-2R-methylbutyric acid is 
obtained. 
(b) 1-(4-Methoxycarbonyl-2R-methylbutanoyl)-4-S-phenylthio-L-proline 
Substituting 4-methoxycarbonyl-2-R-methylbutyric acid for 
3-methoxycarbonyl-2-R-methylpropionic acid while following the procedure 
of Example 22(b), then 
1-(4-methoxycarbonyl-2R-methylbutanoyl)-4-S-phenylthio-L-proline is 
obtained. 
EXAMPLE 24 
1-((RS)-3-methoxycarbonyl-5-phenyl-2R-methylpentanoyl)-4-S-phenylthio-L-pro 
line 
(a) (RS)-3-Methoxycarbonyl-5-phenyl-2R-methylpentanoic acid 
3-methoxycarbonyl-2R-methylpropionic acid (46 g, 10 mmoles) is added to a 
one molar solution of lithium diisopropylamide in tetrahydrofuran (20 ml) 
chilled at -78.degree.. The enolate is allowed to form for forty minutes 
at -78.degree.. Phenethylbromide (185 g, 10 mmole) is added and the 
reaction mixture is allowed to reach 4.degree. C. and maintained at this 
temperature until the reaction is complete as monitored by tlc. The 
reaction mixture is diluted with ethyl acetate and washed with 10% aqueous 
bisulfate and water. The organic layer is dried (MgSO.sub.4) and 
concentrated to dryness to give 
(RS)-3-methoxycarbonyl-5-phenyl-2R-methylpentanoic acid. 
(b) 
1-((RS)-3-methoxycarbonyl-5-phenyl-2R-methylpentanoyl)-4-S-phenylthio-L-pr 
oline. 
Substituting (RS)-3-methoxycarbonyl-5-phenyl-2R-methylpentanoic acid for 
3-methoxycarbonyl-2-R-methylpropionic acid while following the procedure 
of Example 22(b) then 
1-((RS)-3-methoxycarbonyl-5-phenyl-2R-methylpentanoyl)-4-S-phenylthio-L-pr 
oline is obtained. 
EXAMPLE 25 
1-(4-Methoxycarbonyl-6-phenyl-2-R-methylhexanoyl)-4-S-phenylthio-L-proline 
(a) 4-Methoxycarbonyl-6-phenyl-2-R-methylhexanoic acid 
By substituting 4-methoxycarbonyl-2-R-methylbutyric acid for the 
3-methoxycarbonyl-2-R-methylpropionic acid in the procedure of Example 
24(a), then 4-methoxycarbonyl-6-phenyl-2-R-methylhexanoic acid is 
obtained. 
(b) 
1-(4-Methoxycarbonyl-6-phenyl-2-R-methylhexanoyl)-4-S-phenylthio-L-proline 
By substituting 4-methoxycarbonyl-6-phenyl-2-R-methylhexanoic acid for 
3-methoxycarbonyl-2-R-methylpropionic acid while following the procedure 
of Example 22(b) then 
1-(4-methoxycarbonyl-6-phenyl-2-R-methylhexanoyl)-4-S-phenylthio-L-proline 
is obtained. 
EXAMPLE 26 
1-(4-Ethoxycarbonyl-2-methyloctanoyl)-4-S-phenylthio-L-proline 
(a) 4-Ethoxycarbonyl-2-methyloctanoic acid benzyl ester 
4,4-Diethoxycarbonyl-2-methylbutyric acid benzyl ester [prepared by Michael 
condensation of benzylmethacrylate and malonic ester as per J. Am. Chem. 
Soc., 52, 4598 (1930)] (3.36 g, 10 mmole) is added to a solution of 0.23 g 
of sodium in ethanol (3 ml) chilled to 10.degree. C. Butyl iodide (1.85 g, 
10 mmoles) is added and the mixture is refluxed for four hours. The 
solvent is removed in vacuo and the mixture is distilled in vacuo to yield 
4,4-diethoxycarbonyl-2-methyloctanoic acid benzyl ester. 
This material (3 mmole) and 1,4-diazabicyclo[2.2.2]octane (30 mmole) are 
refluxed in O-xylene (45 mmole) for thirty hours. The mixture is 
fractionated in vacuo to yield 4-ethoxycarbonyl-2-methyloctanoic acid 
benzyl ester. 
(b) 4-Ethoxycarbonyl-2-methyloctanoic acid 
4-ethoxycarbonyl-2-methyloctanoic acid benzyl ester (10 g) is dissolved in 
ethanol (100 ml), 10% palladium on charcoal (2 g) is added, and the 
mixture is hydrogenated until complete removal of the benzyl ester is 
achieved to yield 4-ethoxycarbonyl-2-methyloctanoic acid. 
(c) 1-(4-ethoxycarbonyl-2-methyloctanoyl)-4-S-phenylthio-L-proline 
By substituting 4-ethoxycarbonyl-2-methyloctanoic acid for 
3-methoxycarbonyl-2-R-methylpropionic acid while following the procedure 
of Example 22(b) then 
1-(4-ethoxycarbonyl-2-methyloctanoyl)-4-S-phenylthio-L-proline is 
obtained. 
EXAMPLES 27-56 
By following the procedure of Example 22 but using a proline of Column I in 
place of the cis-4-phenylthio-L-proline, of Example 22(b); and using the 
acid compound of Column II in place of the 
3-methoxycarbonyl-2-R-methylpropionic acid of Example 22(b) then the 
product of Column III is obtained. 
__________________________________________________________________________ 
Column I 
##STR30## 
Column II 
##STR31## 
Column III 
##STR32## 
Example 
R.sub.1 R.sub.2 R.sub.3 
R.sub.4 n 
__________________________________________________________________________ 
27 CH.sub.3 H OCH.sub.3 
F 1 
28 
##STR33## H OCH.sub.3 
Br 1 
29 H CH.sub.3 OCH.sub.3 
Br 1 
30 CH.sub.3 H OCH.sub.3 
##STR34## 1 
31 
##STR35## H OCH.sub.3 
Cl 1 
32 
##STR36## H OCH.sub.3 
O 1 
33 
##STR37## H OCH.sub.3 
NNN 1 
34 H H OCH.sub.3 
##STR38## 1 
35 H H OCH.sub.3 
##STR39## 1 
36 H H OCH.sub.3 
##STR40## 1 
37 H H OCH.sub.3 
##STR41## 1 
38 H H OCH.sub.3 
##STR42## 1 
39 H H OCH.sub.3 
##STR43## 1 
40 H H OCH.sub.3 
##STR44## 1 
41 
##STR45## H OCH.sub.3 
F 1 
42 H H OCH.sub.3 
OCH.sub.3 1 
43 H H OCH.sub.3 
SCH.sub.3 1 
44 H H OCH.sub.3 
OCH.sub.2 CH.sub.2 CH.sub.3 
1 
45 H H OCH.sub.3 
OC(CH.sub.3).sub.3 
1 
46 H H OCH.sub.3 
##STR46## 1 
47 H H OCH.sub.3 
##STR47## 1 
48 H H OCH.sub.3 
##STR48## 1 
49 H H OCH.sub.3 
##STR49## 1 
50 H H OCH.sub.3 
##STR50## 1 
50A H H OCH.sub.3 
##STR51## 1 
51 H H OCH.sub.3 
##STR52## 1 
51A H H OCH.sub.3 
##STR53## 1 
52 C.sub.2 H.sub.5 
H OCH.sub.3 
O 1 
53 
##STR54## H OCH.sub.2 CH.sub.3 
Cl 1 
54 
##STR55## CH.sub.3 OCH.sub.2 CH.sub.3 
##STR56## 1 
55 H 
##STR57## OCH.sub.3 
##STR58## 1 
56 H 
##STR59## OCH.sub.3 
##STR60## 1 
__________________________________________________________________________ 
EXAMPLES 57-69 
By following the procedure of Example 22 but using a proline of Column I in 
place of the cis-4-phenyl-thio-L-proline, of Example 22(b); and using the 
acid compound of Column II in place of the 
3-methoxy-carbonyl-2-R-methylpropionic acid of Example 22(b) then the 
product of Column III is obtained. 
__________________________________________________________________________ 
Column I 
##STR61## 
Column II 
##STR62## 
Column III 
##STR63## 
Example 
R.sub.1 R.sub.2 
R.sub.3 
R.sub.7 n 
__________________________________________________________________________ 
57 
##STR64## H OCH.sub.3 
Cl 1 
58 H CH.sub. 3 
OCH.sub.3 
Cl 0 
59 H H OCH.sub.3 
Br 1 
60 H H OCH.sub.3 
F 1 
61 H H OCH.sub.3 
OCH.sub.3 1 
62 H H OCH.sub.3 
##STR65## 1 
63 H H OCH.sub.3 
##STR66## 1 
64 H H OCH.sub.3 
##STR67## 1 
65 H H OCH.sub.3 
##STR68## 1 
65A H H OCH.sub.3 
##STR69## 1 
66 H H OCH.sub.3 
##STR70## 1 
66A H H OCH.sub.3 
##STR71## 1 
67 CH.sub.3 H OCH.sub.3 
Cl 1 
68 H H OCH.sub.3 
OCH.sub.3 0 
69 H CH.sub.3 
OCH.sub.3 
##STR72## 0 
70 H CH.sub.3 
OCH.sub.3 
##STR73## 0 
71 H CH.sub.3 
OCH.sub.3 
##STR74## 0 
72 H CH.sub.3 
OCH.sub.3 
##STR75## 
__________________________________________________________________________ 
In Examples 70-72, R.sub.7 is Y--R.sub.8 where the R.sub.8 groups join to 
complete an unsubstituted 5- or 6-membered ring or such ring wherein one 
or more carbon atoms are substituted by a lower alkyl or di(lower alkyl) 
group. 
EXAMPLES 73-78 
By following the procedure of Example 22 but using a proline of Column I in 
place of the cis-4-phenyl-thio-L-proline, of Example 22(b); and using the 
acid compound of Column II in place of the 
3-methoxy-carbonyl-2-R-methylpropionic acid of Example 22(b) then the 
product of Column III is obtained. 
______________________________________ 
Column I 
##STR76## 
Column II 
##STR77## 
Column III 
##STR78## 
Ex. R.sub.1 R.sub.2 R.sub.3 
R.sub.9 n 
______________________________________ 
73 
##STR79## H OCH.sub.3 
O 1 
74 H H OCH.sub.3 
##STR80## 
0 
75 H H OCH.sub.3 
##STR81## 
1 
76 H H OCH.sub.3 
O 0 
77 CH.sub.3 H OCH.sub.3 
##STR82## 
1 
78 CH.sub.3 CH.sub.3 
OCH.sub.3 
##STR83## 
0 
______________________________________ 
EXAMPLES 79-130 
By following the procedure of Example 3(b) but using a product of Column 
III in Examples 27-78 in place of the 
1-(3-methoxycarbonyl-2-methyl-propanoyl)-4,4-ethylenedithio-L-proline of 
Example 3(b), the corresponding free acid is obtained.