The total synthesis of ritipenems. Construction of penem thiazoline ring by incorporation of two 2C units of glycolic acid.

Abstract Short syntheses of Ritipenem Acoxyl 1a and Ritipenen 1b are reported. The syntheses start from (R)-4-acetoxy-(S)-3[(R)-1-(t-butyldimethylsilyloxy)ethyl]azetidin-2-one 3 and are based on the incorporation of two 2C units obtained by manipulation of glicolyc acid 4 .