Synthesis of α‐hydroxy‐β‐lactams

A convenient synthesis of α‐hydroxy‐β‐lactams has been devised that involves the annelation of an inline with benzyloxyacetyl chloride and triethylamine and subsequent hydrogenolysis in the presence of palladium on carbon. In most cases a cis‐β‐lactam was obtained. A thioimidate can also be used as the imino component in the annelation reaction but the hydrogenolysis step fails. The annelation of the appropriate thiazoline to a 6‐epi‐penicillin derivative occurred much more readily with benzyloxyacetyl chloride than with azidoacetyl chloride.