Leptomycins A and B, new antifungal antibiotics. II. Structure elucidation

The structures of new antifungal antibiotics, leptomycins A and B produced by Streptomyces sp. ATS1287 were determined as described below (Fig. 1) on the basis of their spectral and chemical character. Leptomycins have unique structures which belong to the unsaturated, branched-chain fatty acids with delta-lactone rings at the end.