CHEMISTRY OF UNUSUAL MACROLIDES .1. PREPARATION OF THE AGLYCONS OF CONCANAMYCIN-A AND ELAIOPHYLIN

The aglycons of the concanamycins (1, 2) and elaiophylin (11) have been prepared for direct comparison to the vacuolar-type ATPase inhibitor bafilomycin A1 (10). The deglycosylation was achieved by acid hydrolysis in the absence of MeOH, while acid-catalyzed methanolysis proceed ed with unexpected displacement of carbohydrate residues rather than methoxy groups. Structure assignments of the derivatives were made with the help of one- and two-dimensional NMR studies. Especially helpful were the 9-O-acetylated concanamycin derivatives because they showed reduced flexibility of the macrolactone ring. As a result of a detailed analysis of the O-methyl derivatives of elaiolide (15) the structure of an earlier reported aglycon derivative of elaiophylin has to be revised to 12.