PROCESS FOR MANUFACTURING SIMVASTATIN FROM LOVASTATIN OR MEVINOLINIC ACID

Preparation of simvastatin of formula (I) comprises (i) treating a compound of formula (I') with an alkyl amide of formula R3NH2 to produce a compound of formula (III): R = a group of formula (a) or (b): R2 = H, Na, K or NH4; R3 = 3-6C n-alkyl or cycloalkyl; (ii) treating (III) with a methylating agent to produce a compound of formula (IV) and (iii) removing R3 and closing the pyranone ring to produce simvastatin. In step (iii) the R3 group is preferably cleaved by treating (IV) with a strong base e.g. sodium hydroxide followed by treatment with ammonium hydroxide and then treating with an organic solvent e.g. toluene and heating to give (IIa). The methylating agent in step (ii) is a methyl halide e.g. methyl iodide and methylation is in the presence of a base e.g. lithium pyrrolidide.