Translactonization in Erythromycins

Abstract

When erythromycin A is heated in diethylamine-acetic acid. an erythromycin hemiketal is obtained, which can be further transformed into a new enol ether and spiroketal. The new euol ether is also obtained in equilibrium with the normal one on heating erythromycin A or B in pyridine-acetic acid. The novel compounds. which will be called pseudoerythromycin derivatives. are characterized by a translactonization between the eu-hydroxyl and the lactone group. Their structure was proved by mass and IH and 13C NMR spectrometry. by acetylation experiments, and by degradation with lead tetraacetate.