Carboxyalkyl Dipeptides and Anti-Hypertensive Use Thereof

Mix S-benzyl-L-cysteine ethyl ester hydrochloride (8.28 g) with NaHCO.sub.3 solution until basic. Extract with dichloromethane, dry with MgSO.sub.4, and concentrate to dryness at room temperature. Dissolve the residue in tetrahydrofuran (80 ml) containing pyruvoyl-L-proline (2.1 g) and 5 Angstrom molecular sieves (4 g). Stir for 2 days and then add, dropwise over 4 hours, a solution of sodium cyanoborohydride in ethanol (20 ml). Stir for 18 hours, filter, and concentrate the filtrate to dryness. Partition the residue between water and dichloromethane. Absorb the aqueous phase on a sulfonic acid ion exchange resin and elute with 4% pyridine in water. Concentrate to dryness. Dissolve the residue in a mixture of methanol (5 ml) and ether (1500 ml) . Acidify this solution with 3.5M HCl in ether and filter the resulting precipitate to obtain the title compound (2.5 g), m.p. 90.degree.-100.degree. C. and [.theta.].sub.D.sup.26 =-73.4.degree. (1%, H.sub.2 O).

Following the procedure of Example 1, react O-benzyl-L-serine ethyl ester hydrochloride (5 g) with pyruvoyl-L-proline (1.26 g) to yield the title compound (1.6 g), m.p. 90.degree.-100.degree. and [.theta.].sub.D.sup.26 =-71.3.degree. (1%, H.sub.2 O).

Following the procedure of Example 1, substitute S-4-methylbenzyl-L-cysteine ethyl ester for S-benzyl-L-cysteine ethyl ester and substitute N-pyruvoyl-(S)-perhydroindole for N-pyruvoyl-L-proline to obtain the title compound, m.p. 55.degree.-60.degree. C.

Step 1. 2-Bromo-4-(4-carboxyphenyl)butyric acid: Heat ethyl 2-bromo-4-(4-cyanophenyl)butyrate (16.5 g) in 47-49% hydrobromic acid (160 ml) under reflux for 16 hr. Cool the reaction mixture and dilute with ice to give the title compound, a light tan solid (15.07 g), m.p. 172.degree.-176.degree..

Step 2. Ethyl 2-bromo-4-(4-ethoxycarbonylphenyl)butyrate: Combine the product of Step 1 (15.07 g), 1,3-dicyclohexylcarbodiimide (22.0 g) and 4-dimethylaminopyridine (1.28 g) in dichloromethane (CH.sub.2 Cl.sub.2) (150 ml) and treat with absolute ethanol (20 ml) at 0.degree.-5.degree. C. and stir for 18 hr. Filter the reaction mixture and concentrate the filtrate in vacuo. Place the residue on a column of silica gel (3 L) and elute with hexane:EtOAc 9:1 to give the title compound, a yellow oil (16.90 g).

Step 3. N-[1(R)- and 1(S)-Ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)-alanine t-butyl esters: Heat the product of Step 2 (16.90 g) and (S)-alanine t-butyl ester hydrochloride (8.05 g) in dimethylformamide (DMF) (80 ml) and triethylamine (40 ml) at 70.degree. for 20 hr. Concentrate the reaction mixture in vacuo and partition the residue between ethyl acetate (EtOAc) and H.sub.2 O. Dry (MgSO.sub.4) the EtOAc and concentrate in vacuo to give an amber oil (15.86 g). Chromatograph the mixture (8.0 g) on Waters Prep 500 (2 cartridges) using hexane:ethyl acetate 19:1 and 9:1 to give N-[1(R)-ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)-alanine t-butyl ester, a pale yellow oil (1.08 g), [.alpha.].sub.D.sup.26 =-21.6.degree. (MeOH) and N-[1(S)-ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)-alanine t-butyl ester, a pale yellow oil (1.42 g), [.alpha.].sub.D.sup.26 =-4.6.degree. (MeOH) and overlaps (0.1 g).

Step 4. N-[1(S)-Ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)alanine: Treat N-[1(S)-ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)-alanine t-butyl ester (2.81 g) in CH.sub.2 Cl.sub.2 (40 ml) at 0.degree.-5.degree. with trifluoroacetic acid (TFA) (30 ml). Stir the resulting mixture at 0.degree.-5.degree. for 0.5 hr., warm to room temperature and stir for 6 hr. Concentrate the reaction mixture in vacuo and chromatograph the residue on a column of silica gel (2 L), eluting with CHCl.sub.3 :i-PrOH:7% NH.sub.4 OH (1:1:1, organic phase) to give the title compound, a white solid (2.06 g), m.p. 145.degree.-147.degree., [.alpha.].sub.D.sup.26 =-33.7.degree. (MeOH).

Step 5. 1-[N-[1(S)-Ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl-(S)-alanyl]-cis ,syn-perhydroindole-2(S)-carboxylic acid t-butyl ester: Add cis,syn-perhydroindole-2(S)-carboxylic acid t-butyl ester (1.28 g) in DMF (10 ml) to the product of Step 4 (2.00 g), DEC (1.10 g) and HOBT (0.90 g). Add N-methylmorpholine (0.63 ml) and stir the resulting mixture at room temperature for 20 hr. Concentrate the reaction mixture in vacuo and partition between EtOAc and H.sub.2 O. Dry (MgSO.sub.4) the EtOAc and concentrate in vacuo to give a pale amber residue. Chromatograph this residue on a column of silica gel (2L), eluting with EtOAc:hexane 1:1 to give the title compound, a colorless oil (2.48 g), [.alpha.].sub.D.sup.26 =-52.4.degree. (MeOH).

Step 6. 1-[N-[1(S)-Ethoxycarbonyl-3-(4-ethoxycarbonylphenyl)propyl]-(S)-alanyl]-ci s,syn-perhydroindole-2(S)-carboxylic acid: Treat the product of Step 5 (2.40 g) in CH.sub.2 Cl.sub.2 (40 ml) at 0.degree.-5.degree. with TFA (25 ml). Stir for 0.5 hr., warm to room temperature and stir for 6 hr. Concentrate the reaction mixture in vacuo and chromatograph the residue on a column of silica gel (2 L), eluting with CHCl.sub.3 : i-PrOH:7% NH.sub.4O H (1:1:1, organic phase) to give the title compound, a white foam (2.09 g), [.alpha.].sub.D.sup.26 =-24.4.degree. (MeOH).

Treat the product of Example 5 (1.01 g) in MeOH (40 ml) at 0.degree.-5.degree. with 1N NaOH (6.0 ml) for 2 hr. Warm the mixture to room temperature and stir for 18 hr. Concentrate the mixture under nitrogen to approximately 10 ml and dilute with H.sub.2 O (10 ml). Stir for 4 hr., cool the reaction mixture to 0.degree.-5.degree. and treat with 1N HCl to give the title compound, a white solid (0.81 g), [.alpha.].sub.D.sup.26 =-35.6.degree. (MeOH:1N NaOH 3:1).

The compounds of this invention are useful in view of their pharmacological properties. In particular, they possess activity as antihypertensive agents as evidenced by their ability to reduce blood pressure in mammals, including humans, in which the blood pressure has become abnormally elevated.

The compounds of the present invention can be combined with pharmaceutical carriers and administered in a variety of well known pharmaceutical forms suitable for oral and parenteral administration to provide compositions useful in the treatment of cardiovascular disorders and particularly mammalian hypertension.

The effective dose (ED.sub.50) of the compounds of this invention will typically be in the range of about 0.01 to about 30 mg/kg, preferably about 0.1 to about 10 mg/kg, of mammalian weight, administered in single or divided doses. The exact dose to be administered is dependent upon where the particular compound lies within the above quoted range, as well as upon the age, weight and condition of the individual.

Generally, in treating humans, the compounds of this invention may be administered to ptients in need of such treatment in a dosage range of 5 to 500 mg per patient generally given several times, thus giving a total daily dose of from 5 to 2000 mg per day. Also, the compounds of this invention may be given in combination with diuretics or other antihypertensives. Typically, these are combinations whose individual per day dosages range from one-fifth of the minimally recommended clinical dosages to the maximum recommended levels for the entities when they are given singly. Examples of such diuretics or other antihypertensives are hydrochlorothiazide, chlorothiazide, ethacrynic acid, amiloride, furosemide, propanolol, timolol and methyldopa.

The composition containing the compounds of this invention will preferably contain from about 5 to about 250 mg of the active compound per dosage unit. These compositions are most preferably administered orally. Typical formulations for oral administration are those such as tablets, capsules, syrups, elixirs or suspensions. Typical injectable formulations include solutions and suspensions.

Typical acceptable pharmaceutical carriers for use in the formulations described above are exemplified by: sugars such as lactose, sucrose, mannitol and sorbitol; starches such as corn starch, tapioca starch and potato starch; cellulose and derivatives such as sodium carboxymethyl cellulose, ethyl cellulose and methyl cellulose; calcium phosphates such as dicalcium phosphate and tri-calcium phosphate; sodium sulfate; calcium sulfate; polyvinylpyrrolidone; polyvinyl alcohol; stearic acid; alkaline earth metal stearates such as magnesium stearate and calcium stearate; stearic acid; vegetable oils such as peanut oil, cottonseed oil, sesame oil, olive oil and corn oil; non-ionic, cationic and anionic surfuctants; ethylene glycol polymers; betacyclodextrin; fatty alcohols and hydrolyzed cereal solids; as well as other non-toxic compatible fillers, binders, disintegrants, buffers, preservatives, antioxidants, lubricants, flavoring agents, and the like commonly used in pharmaceutical formulations.

The following examples describe in detail compositions that are illustrative of the present invention. It will be apparent to those skilled in the art that many modifications, both of materials and methods, may be practiced without departing from the purpose and intent of this disclosure.

In the following examples, the active ingredient is one of the compounds previously named.

Blend the active ingredient, lactose and corn starch until uniform; then blend the magnesium stearate into the resulting powder. Encapsulate the mixture into suitable sized two-piece hard gelatin capsules.

Blend the active ingredient with the lactose until uniform. Blend the smaller quantity of corn starch with the water and add the resulting corn starch paste, then mix until a uniform wet mass is formed. Add the remaining corn starch to the remaining wet mass and mix until uniform granules are obtained. Screen the granules through a suitable milling machine, using a 3/4 inch stainless steel screen. Dry the milled granules in a suitable drying oven until the desired moisture content is obtained. Mill the dried granules through a suitable milling machine using a 16 mesh stainless steel screen. Blend in the magnesium stearate and compress the resulting mixture into tablets of desired shape, thickness, hardness and disintegration.

Dissolve the p-hydroxybenzoates in a portion of water for injection at 60.degree.-70.degree. C. and cool the solution to 25.degree.-35.degree. C. Charge and dissolve all other excipients and the active ingredient. Bring the solution to final volume, filter it through a sterilizing membrane and fill into sterile containers.