The chemistry of erythromycin. Reactions of erythromycin A imine and its 6-methyl ether with aldehydes and hydrazines

Abstract

Erythromycin imine (3) and its 6-methyl ether (6) are multifunctional N-unsubstituted imines, which, in contrast to most unsubstituted imines, are readily isolable and relatively stable towards hydrolysis. With aldehydes in ethanol, the imines react quite differently: the imine (3) reacts with aliphatic and aromatic aldehydes to give predominantly the 9,11-cyclic imines (9), whereas the ether (6) reacts with aliphatic aldehydes to give N-(1-ethoxyalkyl)imines (13) and with benzaldehyde to give a 9,12-epoxy Schiff's base derivative (12). The imines also differ in their reactivities towards hydrazine derivatives: the imine (3) readily reacts with monosubstituted hydrazines to form erythromycin hydrazone derivatives, whereas the ether (6), in common with erythromycin (1), is unreactive towards these reagents. A rationale for the different modes of reaction of compounds (3) and (6) is discussed.