Patent ID: 6995277

Claim:
A process for preparing simvastatin with a specified simvastatin dimer content, comprising the steps of: a) lactonizing an ammonium salt of simvastatin in aromatic hydrocarbon at a concentration of less than about 60 g/l to form a simvastatin; b) dissolving the simvastatin in at least one solvent selected from the group consisting of toluene, ethylacetate, tetrahydrofuran, and benzene and precipitating the dissolved simvastatin with an anti-solvent selected from the group consisting of pentane, hexane, heptane, cyclohexane and petroleum ether; c) isolating the crystallized simvastatin; d) dissolving the crystallized simvastatin in at least one solvent selected from the group consisting of toluene, ethylacetate, tetrahydrofuran, and benzene and precipitating the dissolved simvastatin with an anti-solvent selected from the group consisting of pentane, hexane, heptane, cyclohexane and petroleum ether; and e) isolating the recrystallized simvastatin, wherein the recrystallized simvastatin contains a simvastatin dimer content of less than 0.2% wt.