Studies on Anti-MRSA Parenteral Cephalosporins

IV. A Novel Water-soluble N-Phosphono Type Prodrug for Parenteral Administration

Abstract

A systematic approach for improving the water-solubility of anti-MRSA (methicillin-resistant Staphylococcus aureus) cephalosporin derivatives is described. We first tried to improve the water-solubility of 7β-[2-(5-amino-1, 2, 4-thiadiazol-3-yl)-2(Z)-fluoromethoxyimino-acetamido]-3-[(E)-2-(1-methylimidazo[1, 2-b)]pyridazinium-6-yl)thiovinyl]-3-cephem-4-carboxylate (1a) by substitution of the C-3' pharmacophore. Replacement of the C-3' pharmacophore with a 1-methyl-4-pyridinio group improved the water-solubility without decreasing the anti-MRSA activity. Furthermore, we applied the N-modified prodrug strategy to the C-7 acyl group in order to enhance the water-solubility drastically. Among the compounds prepared, the N-phosphono type prodrugs 2a (1-methylimidazo[1, 2-b]pyridazinium derivative) and 2b (1-methyl-4-pyridinio derivative) showed water-solubility appropriate for a product intended for intravenous injection and in vivo anti-MRSA activity comparable to that of vancomycin.