Process for penems

摘要

There is provided a process for the preparation of compounds of formula (I) useful as antibacterials: wherein R represents hydrogen atom or a hydroxy protecting group, which process comprises reacting a compound of formula (II) wherein R is as defined above, with an oxalyl halide in an inert solvent; optionally converting the resultant compound of the formula III wherein R is as defined above and X is a halogen atom into a compound of the formula III in which X represents a hydroxy group by hydrolysis; either (i) treating the compound of formula III in which X is a halogen atom with a compound of the formula IV wherein Y is a hydroxy group in the presence of an acid scavenger or an organic or inorganic base or (ii) treating the compound of the formula III in which X is a hydroxy group, with a compound of the formula IV in which Y is a leaving group in the presence of a base; cyclizing the resultant compound of the formula V wherein R is as defined above and optionally deprotecting the resultant compound of the formula I wherein R is a hydroxy protecting group to obtain a compound of the formula I wherein R is a hydrogen atom.