2-(Alkylthio) penem-3-carboxylic Acids. I. Synthesis of 6-Unsubstituted Penems

Abstract

Treatment of 4-acetoxy-2-azetidinone (9) with various sodium alkyl trithiocarbonates gave 4-[(alkylthio) thiocarbonyl] thioazetidinones 10, which were converted into the phosphoranes 8. Intramolecular Wittig reactions of 8 followed by deblocking yielded penem-3-carboxylic acids 5.