13β-Hydroxylation of Milbemycins by Selenium Dioxide

Abstract
Introduction of a hydroxyl group to milbemycin nucleus was examined. Starting from 5-oxo-5-deoxymilbemycins, 13β-hydroxy-5-oxo-5-deoxymilbemycins were obtained stereo- and regioselectively by selenium dioxide oxidation in formic acid and subsequent acidic hydrolysis. The stereochemistry of the hydroxyl group was elucidated by 1H NMR study.