Enantioselective Synthesis of (2R, 4'R, 8'R)-α-Tocopherol (Vitamin E) Based on Enzymatic Function

Abstract

Syntheses of (S)-chroman-2-carboxaldehyde congener 1 and (S)-chiral isoprene unit 3 were achieved based on the enzymatic acetylation of (±)-chroman-2-methanol 6 and (±)-(2, 3)-anti-2-methyl-3-(p-methoxyphenyl)-1, 3-propane diol 12, respectively. Synthesis of the side-chain part corresponding to (3R, 7R)-3, 7, 11-trimethyldodecan-1-ol 27 was achieved by the couping reaction of (S)-3 and (R)-3, 7-dimethyloctyl iodide 4. The Witting reaction of (3R, 7R)-phosphonium salt 2 derived from (3R, 7R)-27 and (S)-1 gave the olefin 28 which was subjected to cat-alytic hydrogenation to afford (2R, 4' R, 8' R)-α-tocopherol.