PEPTIDE DERIVATIVES AND PROCESS FOR THE PREPARATION THEREOF

Abstract: Novel peptide derivatives and process for the preparation thereof comprising reacting DA-pepsidine or DAV-pepsidine with one of the particular organic acids or reactive derivatives thereof. The new compounds possess pepsin and acid pro­ tease inhibitory activities.

Description: NEW PEPTIDE DERIVATIVES AND PROCESS FOR THE PREPARATION THEREOF This invention relates to novel peptide derivatives and process for the preparation thereof. The novel compounds of the present invention are represented by the general formula: EMI1.1 wherein n is an integer of 1 or 2, and R is a radical selected from the group consisting of carboxy-propanoyl, 2 carboxy-benzoyl, nicotinoyl and benzyloxycarbonyl-leucyl leucyl. The peptide derivatives of the present invention possess a strong pepsin-inhibitory activities and also an acid protease-inhibitory activity such as anti-renin activity and therefore are useful for therapeutic treatment of diseases caused by hyper-secretion of pepsin and for the prophylaxis and treatment of hypertension. According to the present invention, the compounds having the general formula (I) in which n is as defined above and R is carboxy-propanoyl, 2-carboxy-benzoyl or nicotinoyl, can be prepared by the reaction of compound having the formula: EMI2.1 wherein n is as defined above, with an organic carboxylic acid selected from the group consisting of succinic, phthalic and nicotinic acids or reactive derivatives thereof. Examples of the reactive derivatives of the above organic acids include acid anhydrides, "acid halides and the like. In case of using the organic acid in free form, the above reaction is advantageously effected in the presence of a condensing agent known for the amide forming reaction. The reaction may be carried out according to the conventional procedure used in the amide forming reaction well known in the art. A compound of formula (I) in which n is an integer of 1 or 2 and R stands for benzyloxycarbonyl-leucyl-leucyl, may be obtained first by reacting a compound of the formula (II) with a N-protecting leucine ester, followed by splitting off the protecting group of the product. The resulting leucyl-derivative is then reacted with carboxy-benzoylleucine -ester to obtain the compound of formula (I) wherein n is as defined above and R stands for benzyloxycarbonylleucyl-leucyl. The kind of the N-protecting groups and alcohol moieties of the reactive leucine ester to be used for the reaction and the condition of the reaction may suitably be chosen upon the knowledges for the synthesis of peptides known by those skilled in the art. The starting material of the formula (II) used in the present invention is disclosed in the specification of Japanese Patent Application Laid-open No.67791/76. Thus, they may be obtained by the action of, strain of a bacterium belonging to Bacillus sp., e.g., Bacillus pumilus, Kawaguchi (Ferm-p-2677) EF49-210, to the known N-acyl-pentapeptides, such as Pepsidines A, B and C, and Pepstatines, which are obtained by cultivation of various streptomyces ESee; Agr. Biol. Chem. Japan, 40(3) 451 (1976)]. In above patent specification, the compound of the formula (II) in which n is 1 or 2, is designated as DAV-pepsidine and DA-pepsidine, respectively. The following Examples will specifically illustrate embodiment of the present'invention, however,should not be recognized as to limit the scopes of this invention. Example 1 Preparation of N-3-carboxypropanoyl-DAV-pepsidine (formula I; R = 3-carboxypropanoyl, n = 1) Three-fold molar amount (530 mg)ofsuccinic anhydride was added to an aqueous solution (36 ml) of DAV-pepsidine (formula II; n = 1) (0.9 g). The mixture obtained was stirred for three hours at a room temperature while keeping pH 8.5 with addition of 5N aqueous sodium hydroxide solution. When the reaction was over, the reaction solution was extracted three times with an equal volume of n-butanol. The combined extracts were concentrated to dryness. The residue was dissolved in ethanol. With addition of ethyl ether to the ethanol solution, an amorphous powder (980 mg) separated out was recovered by filtration. It was purified by column chromatography on silica gel, using as eluting solvent a mixture consisting of n-butanol : acetic acid water : n-butyl acetate (4 : 1 : 1 : 4 by volume), the solvent being hereinafter designated as "BAWB-Solvent". N-3carboxypropanoyl-DAV-pepsidine (830 mg; 77.0%) was thus obtained in a form of white powder melting at 153'- 158"C. with deeomposition. Elementary analysis: as C28H48N4 8 rH2 C H N Calculated (%) : 54.98 8.40 9.16 Found (%) : 54.98 8.59 8.77 TLC: Rf = 0.45 on Kiesel Gel 60G254 Plate (BAWB-Solvent) Example 2 Preparation of N-2-carboxybenzoyl-DAV-pepsidine (formula I; R = carboxybenzoyl, n = 1) To an aqueous solution (32 ml) of DAV-pepsidine (0.8 g) was added an equimolar amount (235 mg) of phthalic anhydride. Further procedures were then followed in accordance with those mentioned in the preceding Example 1. There was thus obtained N-2-carboxybenzoyl-DAV-pepsidine (646 mg; 62%) in a white powder, which had the melting point of 158'- 162 C with decomposition. Elementary analysis: as C32H50NLI010.H20 C H N Calculated (%) 57.47 7.8LI 8.38 Found (%) : 57.76 7.69 8.17 TLC: Rf = 0.46 on Kiesel Gel 60G254 Plate (BAWB-Solvent) Example 3 Preparation of N-nicotinoyl-DAV-pepsidine (formula I; R = nicotinoyl, n = 1) To an aqueous solution (90 ml) which contained 0.9 g of DAB-pepsidine was added 3.5-fold molar amount (1110 mg) of nicotinoyl chloride hydrochloride. Further procedures were then followed with those mentioned in the above Example 1, with exception that a mixture consisting of n-butanol, acetic acid and water (3 : 1 : 1 by volume) was used as the eluting solvent in the chromatography. There was thus obtained N-nicotinoyl-DAV-pepsidine (597 mg; 54.9.%) in a white powder which had. the melting point of 1798- 1874C. with decomposition. Elementary analysis: C30H119N11O8 C H N Calculated (%) : 59.29 8.13 11.52 Found (%) : 59.42 8.14 11.33 TLC: Rf = 0.45 on Kiesel Gel254 Plate (BAWB-Solvent) Example 4 Preparation of benzyloxy carbonyl-leucyl-leucyl- DAV-pepsidine (formula I; R = benSyloxycarbonyl-leucyl-leucyl, n = 1) DAV-pepsidine (1.3 g) was dissolved in dimethyl formamide (20 ml). To the solution was added an equimolar amount (1 g) of benzyloxycarbonyl-leucine p-nitrophenyl ester, and the mixture was stirred for 18 hours at room temperature. When the reaction was completed, the reaction mixture was coneen- trated to dryness.. The residue obtained was dissolyed in acetone (300 ml) under warming. The acetone solution was then concentrated up to 100 ml and kept in a refrigerator overnight. There was obtained benzyloxyearbonyl-leucyl-DAVpepsidine (821 mg; 43%) in a white powder. The product (791 mg) obtained above was dissolved in methanol (50 ml). To the resulting solution was added 0.5 palladium on calcium carbonate (300 mg), and the mixture was subjected to catalytic reduction in accordance with a conventional manner. After filtration, the resulting solution was evaproated to dryness. The residue was dissolved in ethanol and the solution thus obtained was cooled to obtain leucyl DAV-pepsidine in a white powder (535 mg; 81%). Leucyl-DAV-pepsidine (535 mg) obtained above was dissolved in dimethylformamide (28 ml). To the solution was added 1.2-fold molar amount (403 mg) of benzyloxycarbonyl leucine p-nitrophenyl ester and the mixture was stirred for 24 hours at room temperature. The reaction mixture was then concentrated to obtain an oily residue, which was triturated with ethyl ether. A white powder (760 mg) formed was filtratered off and recrystallized from acetone. There was thus obtained benzyloxycarbonyl-leucyl-leucyl-DAV-pepsidine (568 mg; 76%) in a white powder, which had the melting point. of 212 - 214°C. with decomposition. Elementary analysis; as C44H74N6011H¸20 C ¯ H N Calculated (%.s : 60.60 8.67 9.64 Found (%) : 60.61 8.72 9.72 TLC: Rf = 0.73 on Kiesel Gel 60G254 Plate (BAWB-Solvent) Example 5 Preparation of N-3-carboxy propanoyl-DA-pepsidine (formula I; R = 3-carboxy-propanoyl, n = 2) The value of 1.2-fold molar amount (179 mg) of succinic anhydride was added to an aqueous solution (36 ml) of DApepsidine (formula II, n = 2) (0.9 g). The mixture was stirred for two hours at room temperature while the pH of said mixture was maintained to 8.5 with addition of 5N aqueous sodium hydroxide solution. After the completion of the reaction, the reaction mixture was concentrated to about 20 ml and acidified to pH 3 - LI with addition of a 10% aqueous citric acid solution under ice-cooling and allowed to stand under ice-cooling for one hour. The resulting precipitate was recovered by filtration and washed with ethyl ether. There was thus obtained N-3-carboxypropanoyl-DA- pepsidine. (825 mg; 78.6%) in the form of white powder, which had the melting point of 2050- 2100 C. with decomposion. Elementary, analysis: C33M59N5011.H20 C H N Calculated (%) : 55.76 8.51 9.85. Found (%) : 55.69 8.39 9.55 TLC: Rf = 0.47 on.Kiesel Gel 60G254 Plate (BAWB-Solvent) Example 6 Preparation of N-2-carboxybenzoyl-DA-pepsidine (formula I; R = carboxybenzoyl, n = 2) To an aqueous solution (32 ml) of DA-pepsidine (0.8 g) was added l.l-fold molar amount (197 mg) of phthalic anhydride. Further procedures were followed in accordance with those mentioned in the preceding Example 5. There was thus obtained N-2-carboxybenzoyl-DA-pepsidine (734 mg; 73.6%) in a form of white powder, the melting point of which was 165- 174 C. Elementary analysis: C37H59N5 ll H20 C H N Calculated (%) : 57.87 8.00 9.12 Found (%) : 57.52 7.84 9.00 TLC: Rf*= = 0.51 on Kiesel Gel 60G254 Plate (BAWB-Solvent) Example 7 Preparation of N-nicotinoyl-DA-pepsidine (formula I; R - nicotinoyl, n = 2) To an aqueous solution (30 ml), which contained 0.9 g of DA-pepsidine,was added three-fold molar amount (786 mg) of nicotinoyl chloride hydrochloride. The mixture was stirred for three hours at room temperature while the pH of mixture was maintained at 8.5 with addition of 5N aqueous sodium hydroxide solution. Thereafter, additional nicotinoyl chloride hydrochloride (158 mg) was again added to the reaction mixture. The pH of the reaction mixture was adjusted to 4 and allowed to stand for one hour under ice-cooling. The precipitate separated out was recovered by filtration and washed with ethyl ether. The product was then purified by column chromatography on silica gel using as eluting solvent a mixture consisting of n-butanol, acetic acid and water (3 : 1 : 1 by volume). There was thus obtained N-nicotinoyl-DA-pepsidine (522 mg; 49.3%) in a form of white powder, the melting point of which was 221 - 226 CC. with decomposition. Elementary analysis: C35H58N6O9.3H2O C H N Calculated (%) : 58.72 8.31 11 74 Found (%) : 58.67 8.35 11.67 TLC: Rf = 0.47 on Kiesel Gel 60G254 Plate (BAWB-Solvent)

Claims: What is claimed is: 1. Peptide derivatives represented by the general formula: EMI11.1 wherein n is an integer of 1 or 2, and R stands for a radical selected from the group consisting of carboxypropanoyl, 2-carboxybenzoyl, nicotinoyl and benzyloxycarbonyl-leucyl-leucyl. 2. The compound according to claim 1, wherein n is 1 and R is 3-carboxypropanoyl. 3. The compound according to claim 1, wherein fl is 1 and R is 2-carboxybenzoyl. 14. The compound according to claim 1, wherein n is 1 and R is nicotinoyl. 5. The compound according to claim 1, wherein n is 1 and R is benzyloxycarbonyl-leucyl-leucyl. 6. The compound according to claim 1, wherein n is 2 and R is 3-carboxypropanoyl. 7. The compound according to claim 1, wherein n is 2 and R is 2-carboxybenzoyl. 8. The compound according to claim 1, wherein n is 2 and R is nicotinoyl. 9. Process for the preparation of peptide derivatives of the general formula (I) in claim 1 wherein n is an interger of 1 or 2 and R is carboxypropanoyl, 2-carboxybenzoyl or nicotinoyl, characterized by reacting the compound of the formula: EMI12.1 wherein n is an integer of 1 or 2 with an organic carboxylic acid selected from the group consisting of succinic, phthalic and nicotinic acids or reactive derivatives thereof. 10. Process for the preparation of peptide derivatives of the general formula (I) in claim 1, wherein n is an integer of 1 or 2 and R is benzyloxycarbonyl-leucyl leucyl, characterized by reacting compound of the formula: EMI13.1 wherein n is an integer of 1 or 2 with an N-protecting leucine ester, splitting.off-the N-protecting group of the resulting product, and then reacting the resulting compound with benzyloRy carbonyl-leucine ester.

Inventors: HASEGAWA, YOSHIKAZU, KUWANA, NORIAKI, NOZU, YUKIO
Applicants: EISAI CO., LTD.
Application year: 1981
Main classification: C07C103
IPC codes: C07K5