Deltamycin A1

Deepoxidation products P1, P2 and P3 of carbomycin A, deltamycin A1 and 4"-phenylacetyldeltamycin showed high in vitro antibacterial and antimycoplasmal activities which were comparable to those of the respective parent compounds. By contrast, the in vitro antimicrobial potencies of angolamycin P1 and rosamicin P1 were about ten-fold lower than those of the parent macrolides. In mice, the increase in the plasma levels of the epoxyenone macrolides due to deepoxidation was highly significant with the P1, P2 and P3 derivatives of carbomycin A and 4"-phenylacetyldeltamycin, whereas angolamycin P1 gave a moderately-improved plasma level compared with angolamycin.

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.

Carbomycin A (deltamycin A4) was deepoxidized to carbomycin A P1 by Streptomyces halstedii subsp. deltae (a deltamycins producer), favorably under anaerobic conditions. Carbomycin A P1 was spontaneously converted to geometric isomers designated carbomycins A P2 and A P3. This type of deepoxidation and subsequent isomerization was not limited to carbomycin A, but generally occurrable in other 16-membered epoxyenone macrolide compounds. Many bacteria and actinomycetes were also found to have an ability to deepoxidize deltamycins reductively. The chemical structures of carbomycins A P1, A P2 and A P3 were elucidated as shown in Fig. 3.