(EN) Racemization of the R(−) isomer of the (2-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-acetic acid methyl ester (Formula II) (also called R clopidogrel) is performed via conversion of a portion thereof to the S(+)isomer and it takes place in an organic solvent selected from alcohols, esters, ketones or ethers, or in their mixtures, in the presence of a base selected from substances of formula R1R2R3R4N+OH″ wherein R1, R2, R3 and R4 are identical or different substituents selected from C1-C5 alkyls or C5, C6 cycloalkyls or aryls, C7-C9 alkyl-cycloalkyls or alkyl-aryls, the molar ratio of the base to the starting substance being 1:1 to 1:10., OMe Cl I Cl<VOMe II.