Alkaline degradation of sulbactam.

Abstract

Alkaline degradation of sodium sulbactam in methanol and in an aqueous solution has been investigated. The degradation in alkaline methanol produced methyl 5-carboxy-6-methyl-6-sulfino-4-aza-2-heptenoate (II) which showed an ultraviolet (UV) absorption maximum at 279 nm. The UV absorption almost disappeared when the solution was acidified with methanolic HCl solution, and reappeared on subsequent realkalization, suggesting interconversion between II and its protonated form. The degradation in aqueous alkaline solutions yielded 5-carboxy-6-methyl-6-sulfino-4-aza-2-heptenoic acid (IV), which showed λmax at 267 nm. IV was further degraded to 2-amino-3-methyl-3-sulfinobutanoic acid and formylacetic acid. The UV absorption of II and IV almost disappeared in aqueous acidic conditions, and reappeared on subsequent realkalization. These changes could be due to the hydrolysis of enamines II and IV to yield methyl formylacetate and formylacetic acid, respectively, in acidic conditions, and to the generation of the corresponding enolate ions on realkalization.