Ro 22-5417, A NEW CLAVAM ANTIBIOTIC FROM STREPTOMYCES CLAVULIGERUSβ

III. ABSOLUTE STEREOCHEMISTRY

Abstract

The complete stereostructure of the new antibiotic Ro 22-5417 has been established as 3-[(3S, 5S)-7-oxo-1-aza-4-oxabicyclo[3.2.0]hept-3-yl]-L-alanine. This result together with the synthesis of an (3R, 5R)-L-analog allowed us to postulate that clavams require the R-configuration at the ring juncture for β-lactamase inhibitory activity, while the opposite S-stereochemistry is essential for antifungal activity.