Alternative Cefazolin Synthesis with a Cephalosporin-Acid Synthetase

Two pathways of combined chemical and biocatalytic synthesis of the antibiotic cefazolin (CEZ) from 7-amino-cephalosporanic acid (7-ACA) with the immobilized recombinant cephalosporin-acid synthetase as the biocatalyst are compared. The first pathway involved chemical substitution with 2-mercapto-5-methylthiadiazole to modify the 3-acetoxy group in 7-ACA with subsequent biocatalytic acylation of the amino group of the product, 7-amino-3-[2-methyl-1,3,4-thiadiazol-5-yl)-thiomethyl]-3-cephem-4-carboxylic acid (TDA), with the methyl ester of 1(Н)-tetrazolylacetic acid. An alternative pathway involved biocatalytic acylation of the 7-ACA amino group to form an intermediate (S-p CEZ) that was chemically transformed into CEZ at the next step without isolation from the reaction mix. Analysis and optimization of each of the biocatalytic processes showed that 7-ACA acylation had a number of important advantages over TDA acylation with respect to the process yield, final concentration of the product in the reaction mix, and the tolerance of the process conditions with respect to enzyme activity and stability. Given the obvious environmental advantages of the process of chemical S-p CEZ transformation into CEZ over the process of TDA production from 7-ACA, we conclude that the second pathway of combined chemical and biocatalytic CEZ synthesis is preferable.