New cephalosporins with 7-acyl groups derived from .BETA.-ketoacids. II. Further modifications of 7-(3-oxobutyrylamino)-cephalosporins.

Abstract
New cephalosporins modified in the acyl part of 7-(3''-oxobutyrylamino)cephalosporins (1) were synthesized by thiolation at the 2''- or the 4''-position, or by transforming the 3''-oxo group into a 3''-imino group. The most active compound in vitro was 3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-7-(4-methylthio-3-oxobutyrylamino)ceph-3-em-4-carboxylic acid (7c), which showed superior in vitro activity against gram-positive and gram-negative bacteria compared to the parent cephalosporin (1b) with the same 3-substituent. The ED50 value for 7c was essentially equal to that of 1b in mice infected with Escherichia coli O-111.

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