Translactonization in Erythromycins

Article abstract of DOI:10.1021/jo00382a004

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 enol 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 C₁₁-hydroxyl and the lactone group.Their structure was proved by mass and 1H and 13C NMR spectrometry, by acetylation experiments, and by degradation with lead tetraacetate.