Studies on 3′-quaternary ammonium cephalosporins—IV. Synthesis and antibacterial activity of 3′-(2-alkyl-3-aminopyrazolium)cephalosporins related to FK037

Abstract The synthesis and in vitro antibacterial activity of 7 β -[( Z )-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido] cephalosporins bearing various 2-alkyl-3-aminopyrazolium groups at the 3-position are described. Antibacterial activity against MRSA was affected by the nature of the substituent at the 2-position on the 3′-aminopyrazolium groups. Among the cephalosporins prepared in this study, 7 β -[( Z )-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3-[3-amino-2-(2-hydroxyethyl)-pyrazolio]methyl-3-cephem-4-carboxylate sulfate ( 23e , FK037) showed extremely potent broad-spectrum activity against both Gram-positive bacteria including MRSA, and Gram-negative bacteria including Pseudomonas aeruginosa . In particular, the in vivo activity against MRSA of FK037 was the highest of all the β-lactam antibiotics tested.