A new reductive acylation of azetidinone disulphide in the route to penems

Abstract The use of triethyl phosphite and the appropriate carboxylic anhydridewas found to constitute an efficient method for the conversion of azetidinyl benzthiazolyl disulphides into acylthioazetidinones, allowing a short synthesis of penem FCE 88891 from its penam-1-oxide precursor.