AT394726B - METHOD FOR PRODUCING L-ALANYL-L-PROLIN DERIVATIVES - Google Patents

Description

AT 394 726 B

The present invention belongs to the field of peptide chemistry and relates to a process for the preparation of L-alanyl-L-proline derivatives of the formula

COOH where R is ethyl or hydrogen, and their pharmaceutically acceptable salts.

The compound of general formula I inhibits the conversion of the decapeptide angiotensin I to angiotensin Π, which plays a role as a blood pressure regulator. The enzyme renin, which is excreted by the kidneys, has an effect on one of the plasma proteins, namely the renin substrate angiotensinogen. The latter is excreted by the liver and decapeptide angiotensin I is cleaved from this substrate. Angiotensin I is converted to angiotensin II by means of the enzyme angiotensinase. The compound of general formula I inhibits the enzyme angiotensinase and is suitable for the treatment of cardiovascular diseases, in particular hypertension

There was a need for a new, technologically and economically improved process for the preparation of L-alanyl-L-proline derivatives of the formula I.

In known processes, L-alanyl-L-proline derivatives of the formula I are obtained by condensing ethyl 4-phenyl-2-oxobutanoate and L-alanyl-L-proline and hydrogenation (US Pat. No. 4,374,829) or by condensing N-Carboxyanhydrid-N- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanine with an L-proline salt (EP-A 215 335).

The process for the preparation of L-alanyl-L-proline derivatives of the general formula I

in which R is ethyl or hydrogen and their pharmaceutically acceptable salts is characterized according to the invention in that Ν, Ο-bistrimethylsilyl-L-proline of the formula II

(H3C) 3SiN r C00Si (CH3) 3 -2-

AT 394 726 B with an N- / l (S) -ethoxycarbonyl-3-phenylpropyl / L-alanine derivative of the general formula ΙΠ

ooc2h5 H NH CH CO Het ffl in which Het is an imidazole-1- or 2-thiobenzothiazole residue, in non-polar organic solvents, such as dioxane, tetrahydrofuran, methylene chloride, preferably tetrahydrofuran, in a temperature range from -10 to +20 ° C and condensed optionally the resulting compound of formula I, wherein R is ethyl, is hydrolyzed into the compound of formula I, wherein R is hydrogen

The present process differs from known processes in the use of N, 0-bis-trimethylsilyl-L-proline of the formula II, which is condensed with an amide or a thioester of the formula HI. The process has the following advantages: the condensation time is shorter, the reaction takes place quantitatively.

The starting compounds Π and ΠΙ are commercially available or can be prepared in a known manner.

The process is explained in more detail using the following examples

Example! N-1 (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanyl-L-proline maleic salt

A solution of 2.8 g of N- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanine, cooled to -5 ° C. in 40 ml of methylene chloride, is mixed with 2.44 g of NJST-carbonyldiimidazole and 3 hours at a Temperature from 0 to -5 ° C stirred. Meanwhile, Ν, Ο-bistrimethylsilylyl-L-proline is prepared in such a way that a suspension of 1.72 g of L-proline in 40 ml of methylene chloride is mixed with 4.2 ml of triethylamine and 3.8 ml of trimethylchlorosilane and half an hour at 40 ° C and stirred for 2 hours at room temperature. The ri, Ο-bistrimethylsilylyl-L-proline produced and cooled in this way is filtered off the triathy! amine.HCl formed and poured into N- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanyl-imidazole. Stirring is continued at a temperature of 0 to -5 ° C. If it is determined by HPLC that the starting compound is no longer present, methylene chloride is evaporated. The residue is mixed with 40 ml of water and 15 ml of ethyl acetate and the pH is adjusted to 8.7 with 2 N NaOH. The aqueous layer is washed once more with 10 ml of ethyl acetate, mixed with NaCl to saturation and with 15 ml of ethyl acetate. PH is adjusted to 4.2 with HCl (1: 1), the layers are separated and the aqueous layer is wildly repeated 7 times extracted with 8 ml each of ethyl acetate. The ethyl acetate layers are dried with Na2S04 and N- / 1 (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanyl-L-proline is precipitated with 1.2 g of maleic acid. The precipitate is filtered off and dried in a vacuum dryer at 40 ° C. 4.1 g (83%) of the title product with a melting point of 143 ° to 147 ° C. are obtained.

Example 2

A solution of 1.4 g of N- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanine in 40 ml of tetrahydrofuran is mixed with 0.85 g of 2-mercaptobenzothiazole, cooled to 0 ° C., 1.2 g Ν, Ν-Dicyclohexylcarbodiimid are added and it is stirred for 3 hours at a temperature of -5 to 0 ° C. The excreted dicyclohexylurea is filtered off and the ester of 2-mercaptobenzothiazole and N- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanine thus produced is cooled (to 0 ° C.) to Ν, Ο-bistrimethylsilyl-L -proline, which was previously prepared by adding a suspension of 1.1 gL-proline in 40 ml of tetrahydrofuran with 2.8 ml of triethylamine and 2.6 ml of trimethylchlorosilane and stirring for 3 hours at room temperature. The stirring is continued until the starting compound is no longer present after HPLC. Tetrahydrofuran is concentrated, the residue is mixed with 20 ml of water and 10 ml of methylene chloride, the pH is adjusted to 8.7 with 2N sodium hydroxide and the layers are separated. The aqueous layer is mixed with sodium chloride until saturated, covered with 15 ml of ethyl acetate and pH is adjusted to 4.3 with hydrochloric acid. The layers are separated and the aqueous layer is extracted with 4 x 8 ml of ethyl acetate. The combined ethyl acetal layers are dried with sodium sulfate and N- / 1 (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanyl-L-proline is precipitated with 0.6 g of maleic acid. The -3-

Claims (2)

AT 394 726 B precipitate is filtered off and dried in vacuo at 40 ° C. 1.5 g (61%) of the title product are obtained. Example 3 N- / l (S) -carboxy-3-phenylpropyl / -L-alanyl-L-proline 1 gN- / l (S) -ethoxycarbonyl-3-phenylpropyl / -L-alanyl-L-proline, obtained after Example 1 is dissolved in 5 ml of ethanol and 5 ml of water containing 320 mg of sodium hydroxide and stirred until complete hydrolysis. After the hydrolysis has ended, the solvent is concentrated under reduced pressure. The residue is dissolved in 10 ml of water saturated with sodium chloride, covered with 10 ml of ethyl acetate and pH is adjusted to 4.2 with a hydrogen chloride solution. The aqueous layer is extracted with ethyl acetate (2 x 10 ml), the combined ethyl acetate layers are dried and concentrated. 0.71 g (76%) of the title product with mp. About 146 to 152 ° C. are obtained. PATENT CLAIM Process for the preparation of L-alanyl-L-proline derivatives of the general formula I C00H I wherein R is ethyl or hydrogen, and their pharmaceutically acceptable salts, characterized in that Ν, Ο-bistrimethylsilyl-L-proIin of the formula Π Π C00Si (CH3) j with an N- / l (S) -ethylcarbonyl-3-phenylpropyl / -L-alanine derivative of the general formula III; 00C2H5: H NH CH CO Het ΙΠ -4- AT 394 726 B wherein Het is an imidazole-1 - or 2-thiobenzothiazole radical means, in non-polar organic solvents, such as dioxane, tetrahydrofuran, methylene chloride, preferably tetrahydrofuran, condensed in a temperature range from -10 to +20 ° C and, if appropriate, the compound of the formula I obtained, in which R denotes ethyl, into the compound of the formula I, where R is hydrogen, hydrolyzes. -5-