Structural elucidation of aculeximycin. III. Planar structure of aculeximycin, belonging to a new class of macrolide antibiotics.

The planar structure of aculeximycin (1) produced by Streptosporangium albidum has been determined by spectral methods and chemical degradations such as 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU)-methanol reaction, ozonolysis, and periodative oxidation. The antibiotic consists of a 30-membered polyhydroxy lactone ring, an alpha, beta-unsaturated ester group, an intramolecular hemiketal, an oligosaccharide (aculexitriose), a neutral sugar and an amino sugar. The structure of aculeximycin is closely related to those of sporaviridins produced by Streptosporangium viridogriseum. We consider that aculeximycin and sporaviridins belong to a new class of macrolide antibiotics, which is different from the polyol macrolides produced by Streptomyces.