Sch-20561

A novel bacterium designated as Aeromonas sp. W-10 produces the antibiotic W-10 complex which comprises of two major and several minor components. The two major components from this complex, Sch 20562 (1) and Sch 20561 (1a), are of biological interest in view of their potent antifungal activity. The chemical degradation studies utilized for the assignment of structure 1 for Sch 20562 are described here. Some of the noteworthy diversity of structural features in this glucosidic cyclic dehydrononapeptide lactone 1 are: an N-terminal (D)-beta-hydroxymyristyl unit, three D-amino acid units, two (E)-alpha-aminocrotonyl units, and an O-alpha-D-glucosyl-N-methyl-L-allo-threonine unit. The structure determination of 1 utilized the selective cleavage of the dehydropeptide units by ozonolysis to form fragments that were sequenced by mass spectrometry. The stereochemistry of the amino acid units were assigned by isolation of the free amino acids from the hydrolysates of the fragments. The stereochemistry of the alpha-aminocrotonyl units and the glucosidic linkage were assigned by nmr spectroscopy and molecular rotation data.

Antibiotic W-10 is a fermentation complex produced by the bacterium Aeromonas 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 biological interest in view of their unique structural features and potent antifungal activity. The chemical degradation studies that were utilized in the assignment of structure 2 for Sch 20561 are described here. The structure determination of 2 made use of the ozonolytic cleavage of the dehydropeptide units to form fragments that were sequenced by mass spectrometry. The cyclic 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 transformation involving the deglucosidation of 1 to form 2.