Process for preparing 6-alkylidene penem derivatives

摘要

Disclosed is a process for the preparation of compounds of formula I, the process comprising; (a) condensing an appropriately substituted aldehyde of formula A?-CHO, with 6-bromo-penem derivative of structure 16 in the presence of a Lewis acid and a mild base, at low temperature to form an intermediate aldol product 18, (b) reacting intermediate 18, with an acid chloride or anhydride of formula (R8)Cl or (R8)2O, or with tetrahalomethane of formula C(X1)4, and triphenyl phosphine, to form intermediate compound 19, (c) converting the intermediate compound 19 to the desired formula I compound by a reductive elimination process.