Process for the preparation of (+)-(1R) -cis-3-oxo-2-pentyl-1-cyclopentaneacetic acid

Process for the preparation of 3-oxo-2-pentyl-1-cyclopentaneacetic acid, or of methyl 3-oxo-2-pentyl-1-cyclopentaneacetate, essentially in the form of their (+)-(1R)-cis configuration isomer, characterized in that it comprises the following steps:

• a) the catalytic hydrogenation, in an appropriate solvent and in the presence of a catalyst composed of a Ru (II) complex comprising chiral ligands which contain a 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) type ligand or a 1,2-bis(2,5-dialkylphospholano)benzenyl (DuPHOS) type ligand, wherein the alkyl is a C.sub.2 or C.sub.3 radical, of a compound of formula ##STR9## wherein M represents a hydrogen atom, an atom of an alkaline or alkaline-earth metal, or a NR.sub.4 group, R representing hydrogen or a lower alkyl radical, to obtain a compound of formula ##STR10## wherein M has the meaning indicated above, essentially in the form of an isomer of (+)-(1R)-cis configuration;
• b) if necessary, the acidification, in a generally known manner, of the compound of formula (II) wherein M represents an atom of an alkaline or alkaline-earth metal or a NR.sub.4 group, R representing hydrogen or a lower alkyl radical, to obtain (+)-(1R)-cis-3-oxo-2-pentyl-1-cyclopentaneacetic acid;
• and
• c) if necessary, the esterification, under appropriate conditions, of the (+)-(1R)-cis-3-oxo-2-pentyl-1-cyclopentaneacetic acid thus obtained to form methyl (+)-(1R)-cis-3-oxo-2-pentyl-1-cyclopentaneacetate.