Biosynthesis of unnatural cephalosporins

Abstract From the Canadian patent

A process for converting a peptide precursor of the ACV type,in which the valine moiety may be replaced by any readily available amino acid,to an unnatural cephalosporin of the type, where R1 is H lower alkyl or functionalized carboxylic group and R2 is H or lower alkyl, in which the precursor is reacted with cyclase, epimerase and a ring expansion enzyme isolated from a cell-free extract of a prokaryotic organism such as Streptomyces clavuligerus. The three enzymes may be immobllized on a suitable support medium and the conversion may be carried out in a continuous mode.