Practical Synthesis of Triethylammonium (Z)-2-[2-(Boc-amino)thiazol-4-yl]-2-(trityloxyimino)acetate, the Side Chain of Cefmatilen

A practical synthesis of triethylammonium (Z)-2-[2-(N-tert-butoxycarbonylamino)thiazol-4-yl]-2-(triphenylmethyloxyimino)acetate (1) which is the C-7 side chain of cefmatilen, a new cephalosporin antibiotic, is described. The conditions were optimized to control the impurity and to increase the yield. Selective acetylation of oxime group before tert-butoxycarbonylation reduced the amount of Boc2O. Compound 1 was synthesized from compound 6 by this improved process in 80% overall yield (12% higher than that for the medicinal process) via a four-reaction sequence (95% per reaction).