Ro 22-5417, a new clavam antibiotic from Streptomyces clavuligerus. III. Absolute stereochemistry.

Abstract
The complete stereostructure of the new antibiotic Ro 22-5417 was 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 a (3R,5R)-L-analog suggested that clavams require the R-configuration at the ring juncture for .beta.-lactamase inhibitory activity; S-stereochemistry is essential for antifungal activity.