Patent ID: 8134026

Claim:
An improved process for the preparation of Cilastatin Acid of formula (I), the process comprises the steps of: i) condensing 7-chloro-2-[[(1S)-2,2-dimethylcyclopropane]carboxamide]-2-heptenoic acid of formula (II) with L-Cysteine in the presence of a base and an alcoholic solvent or an aqueous alcoholic solvent; ii) optionally removing inorganic salts by filtration and concentrating filtrate; iii) optionally adding water; iv) adjusting pH to 2.0 to 4.0; v) extracting the Cilastatin acid into C 4 -C 8 alcohol selected from the group consisting of n-butanol and cyclohexanol; and vi) isolating Cilastatin acid.