Studies on beta-lactam antibiotics. IV. An improved synthesis of 3-(isothiazolylthiomethyl)cephalosporins and its application to new derivatives.

An improved synthesis and in vitro activity of cephalosporins with a (4-carboxy-3-hydroxy-5-isothiazolyl)thiomethyl group at the 3-position and its application to the preparation of new derivatives are described. These compounds showed excellent activity against Gram-negative bacteria including beta-lactamase producing strains. Among them, 2f was the most interesting because of its broad spectrum of antibacterial activity, including Gram-positive bacteria, and its outstanding inhibitory potency against Pseudomonas aeruginosa.