3‐Tocopherylisoxazolines by [2+3] Cycloaddition

Abstract

Abstract New isoxazoline derivatives of α‐tocopherol ( 1 ), the main component of vitamin E, were synthesized in a facile, two‐step sequence consisting of nitration followed by 1,3‐dipolar cycloaddition. 5‐Nitromethyl‐γ‐tocopheryl acetate ( 3 ), obtained from the cheap α‐tocopheryl acetate ( 2 ) by direct nitration in one step, acted as the nitrile oxide precursor in the reaction with various alkenes. The facile conversion proceeded in the presence of equimolar amounts of PhNCO and catalytic amounts of triethylamine. The NMR spectra of the product isoxazolines 5 − 13 , showing strongly temperature‐dependent resonances of the 4′′‐CH, 4‐CH 2 and the acetyl group, are discussed, and the crystal structures of model compounds containing a methyl group instead of the isoprenoid side chain are presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)