Preparation of 6-epi-phenoxymethyl- and 6-epi-benzyl-penicillin

Abstract

Base-catalysed epimerisation at position 6 of N-trimethylsilyl derivatives of phenoxymethylpenicillin benzyl ester in the presence of triethylamine and DBN has been investigated. When triethylamine was used as catalyst a 1,4-thiazepine was obtained in addition to a mixture of the penicillin ester with natural configuration and its 6-epimer. No 1,4-thiazepine was formed when DBN was used as an epimerisation catalyst. The method was also extended to the trimethylsilyl esters of phenoxymethyl- and benzyl-penicillin. The 6-epimers of both penicillins were isolated in ca. 70% yield.