HPLC of cephalosporins and their oxa-derivatives

Summary The presence of the oxygen atom in place of the sulfur atom has significant impact on the polarity of the -lactam derivative. This has been illustrated by direct comparison of HPLC data of 4 different cephalosporin derivatives and their oxa analogues.Acknowledgment. We gratefully acknowledge the cooperation of Drs Yuji Sendo, Toshiro Konoike, Masayuki Murakami and Mitsuru Yoshioka of Shionogi Research Laboratories, Shionogi and Co., Ltd, Fukushima-ku, Osaka, 553, Japan, who synthesized the oxa--lactams and made them available for this study.