Optical resolution of the α-tocopherol spiro dimer and demonstration of its fluxional nature

Abstract

A model compound (1b) for the oxidative dimer of α-tocopherol (vitamin E)(1a) has been shown to undergo fluxion by NMR spectroscopy through a magnetization transfer experiment. This compound has also been resolved at low temperature using an optically active HPLC column. Its rate of racemization parallels the fluxion process suggesting a biradical intermediate and free radicals are shown to be present in non-degassed solutions of (1b). Its crystalline form has been examined with solid-state NMR spectroscopy and X-ray crystallography.