Synthesis and biological activity of 7.BETA.-(2-amino-2-carboxy)- ethylthioacetamido-7.ALPHA.-methoxycephalosporin derivatives.

C-7 and C-3 substituents of a new antibiotic SF-1623 were chemically modified to improve the bioactivity, and substituent effect at C-7 and C-3 was examined on the basis of MIC and ED50 values against selected bacteria. Among a large number of derivatives, MT-141 possessing 2-D-2-amino-2-carboxyethylthioacetamido residue at C-7 and N-methyltetrazolyl-thiomethyl residue at C-3 showed a high order of antibacterial activity in vitro and especially in vivo.