Synthesis and antimicrobial activity of some new sugar-based monocyclic β-lactams

Abstract

The syntheses of some new sugar-based monocyclic β-lactams possessing several other functionalities in addition to the carbohydrate moiety are described. The key step was the Staudinger [2+2] cycloaddition of chiral carbohydrate Schiff base 5 with phthalimidoacetyl chloride to yield the sugar-based monocyclic β-lactam 6 as a single isomer. Treatment of protected β-lactams 6 and 8 with methylhydrazine afforded the free amino β-lactams 9 and 10. Acylation of these free amino β-lactams with benzoyl, phenoxyacetyl, cinnamoyl and phenylacetyl chloride in the presence of pyridine afforded β-lactams 11a-d and 12a-d. Some of these novel β-lactams were found to be active against Staphilococcus citrus, Klebsiella pneumoniae, Escherichia coli and Bacillus subtilis.