Deltamycins, new macrolide antibiotics. III. Chemical structures.

The structures of deltamycins A1,A2,A3 and A4 belonging to the basic macrolide family of antibiotics were determined mainly from their spectral properties. Deltamycin A4 was identified as carbomycin A having an isovaleryl group on the mycarose moiety of the molecule. Deltamycin A1,A2 and A3 possess similarities to the structure of deltamycin A4, but they have acetyl, propionyl and n-butyryl group, respectively, in the place of isovaleryl group of deltamycin A4. These structures were confirmed by chemical synthesis from deltamycin X (4''-O-deacyldeltamycin) and the corresponding acyl chlorides.