A short-step synthesis of orally active carbapenem antibiotic CS-834

An orally bioavailable carbapenem CS-834, which is a pivaloyloxymethyl (POM ) ester-type prodrug and has (R)-5-oxopyrrolidin-3-ylthio moiety at the C-2 position of the 1 beta-methylcarbapenem skeleton, is currently under clini cal trial, We accomplished a short-step synthesis of CS-834 by using phosph orus ylide from the intramolecular Wittig-type reaction in the key step for cyclization to the bicyclic carbapenem system. The POM ester group was fou nd to be suitable for the cyclization conditions.