Patent ID: 7157485

Claim:
A process for the synthesis of compounds of formula (I): wherein R 1 represents hydrogen, linear or branched (C 1 –C 6 )alkyl or benzyl, and R 2 represents a protecting group, wherein 1-(1-cyclohexen-1-yl)-pyrrolidine of formula (III): is reacted with a serine compound of formula (IV): wherein R 1 is as defined for formula (I) and R 3 represents a protecting group, to yield a compound of formula (V): the amine function of the compound of formula (V) is deprotected and the deprotected intermidiate thus obtained is subjected to dehydration, to yield a compound of formula (VI): which is reacted with an alanine compound of formula (VII): wherein R 2 is as defined for formula (I), in an organic solvent, in the presence of an amount of dicyclohexylcarbodiimide of from 1 to 1.2 mol per mol of compound of formula (V) used and an amount of triethylamine of from 1 to 1.2 mol per mol of compound of formula (V) used and optionally in the presence of 1-hydroxybenzotriazole, at a temperature of from 20 to 50° C., to yield, after isolation and recrystallisation, a compound of formula (VIII): which is hydrogenated in the presence of a catalyst, under a hydrogen pressure of from 1 to 30 bars, to yield, after optional deprotection or reprotection of the acid function, the compound of formula (I).