Process for Purification of 3-Alkenylcephem Carboxylic Acid

The present report describes a novel and efficient method for enrichment of 7-amino-3-[(Z)-propen-1-yl]-3-cephem-4-carboxylic acid (1) in a mixture of (Z/E) 7-amino-3[(Z/E)-propen-1-yl]-3-cephem-4-carboxylic acid via formation of 7-β-isopropylideneammonium salt in acidic conditions. This method provides high yield and 7-amino-3-[(Z)-propen-1-yl]-3-cephem-4-carboxylic acid (1) having a low E-isomer content from a mixture containing very high proportion of E-isomer. The usage of these isopropylidene ammonium salts provides a method for separation of mixtures of cephalosporins where geometric isomerism about a double bond exists.