The absolute configuration of berberastine and thalidastine

Optical resolution of (±)-tetrahydrojatrorrhizine using (-)-O,O-di-p-toluoyl-d-tartaric acid gave rise to (+)-tetrahydrojatrorrhizine (6 of high optical purity and of known absolute configuration. Oxidation of this enantiomer with lead tetraacetate, followed by acid hydrolysis, furnished alcohols 10 and 11 in a 2:1 ratio, whose relative stereochemistry was established from their nmr spectra. Iodine oxidation of the major alcohol 10 led to...