Patent ID: 8338621

Claim:
A process for the preparation of a compound of formula (I), wherein the compound of formula (I) is substantially diastereoisomerically pure with respect to stereogenic centers 1* and 2*, and R 1 is C 1-10 alkyl or C 2-6 alkenyl R 2 is C 1-10 alkyl or C 2-6 alkenyl, X is —CONR 4 R 5 , —COOH, —COOR 3 or —CN, R 3 is C 1-10 alkyl; R 4 is hydrogen or C 1-10 alkyl; R 5 is hydrogen or C 1-10 alkyl; which process comprises (a) reacting a substantially optically pure compound of formula (II), wherein X 1 is —CONR 4 R 5 , —COOH, —COOR 3 or —CN Y is a leaving group selected from halogen, sulfonate group or —N 2 + , with a compound of formula (IV) substantially optically pure at stereogenic center 3*, or salts thereof, wherein X 2 is —CONR 4 R 5 , —COOH, —COOR 3 or —CN; in a solvent selected from methanol, isopropanol, tert-butanol, dimethoxyethane, dimethylsulfoxide, dichloromethane, acetonitrile, toluene, and mixtures thereof and in the presence of a base selected from potassium hydride, sodium hydride, sodium methoxide, potassium methoxide, sodium isopropoxide, sodium tert-butoxide, potassium tert-butoxide, potassium carbonate, sodium carbonate, triethylamine, cesium carbonate, and triisopropylamine; and (b) converting the reaction product of II and IV into the compound of the formula I.