Structure elucidation of Sch 20561, a cyclic dehydropeptide lactone - a major component of W-10 antifungal antibiotic

Antibiotic W-10 is a fermentation complex produced by the bacterium Aeromon as sp. W-10. The cyclic dehydropeptide lactones Sch 20562 (1) and Sch 20561 (2) are the major components of this fermentation complex and are of biolo gical interest in view of their unique structural features and potent antif ungal activity. The chemical degradation studies that were utilized in the assignment of structure 2 for Sch 20561 are described here. The structure d etermination of 2 made use bf the ozonolytic cleavage of the dehydropeptide units to form fragments that were sequenced by mass spectrometry. The cycl ic dehydropeptide lactone Sch 20561 (2) was found to be the aglycone of Sch 20562 (1! and these two natural products were correlated by a chemical tra nsformation involving the deglucosidation of 1 to form 2.