STUDIES ON THE CHEMISTRY OF RAPAMYCIN - NOVEL TRANSFORMATIONS UNDER LEWIS-ACID CATALYSIS

The reactivity of rapamycin under mild Lewis-acid catalysis has been investigated. The molecule has been found to be extremely sensitive to basic reagents due to carboxylate elimination beta to the C24 ketone. However, transformations normally effected under basic conditions, such as C-13-C-14 benzilic acid rearrangement Of C28-C30 retroaldol, can be achieved on rapamycin itself by catalysis with ZnCl2 in the appropriate solvent. These are novel transformations that circumvent the protection or masking of reactive functional groups and allow efficient degradation of the molecule for synthetic and biological studies.