Chiral conversion of 6-aminopenicillanic acid into an antibacterial pen-2-em-3-carboxylic acid derivative: absolute structure from X-ray analysis

Abstract

Sulphoxidation of the ester (5) and reaction of the product with 2-mercaptobenzothiazole gave the adduct (6a), which on ozonolysis and mesylation was converted into the ester (7b); stereoselective chlorinolysis and treatment of the product (8) with hydrogen sulphide–triethylamine gave a mixture of the enantiomeric penem esters (3a) and (9a) in which the former predominated.