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All eight stereoisomers of α‐tocopheryl acetate have been synthesized in a state of high chemical and stereoisomeric purity. Key chiral side‐chain intermediates were prepared from (+)‐(S)‐3‐hydroxy‐2‐methylpropanoic acid. New routes to (2R, 4′ RS, 8′ RS)‐α‐tocopheryl acetate, a mixture of four diastereoisomers, were also developed. A sensitive gas chromatographic method was developed to determine the diastereoisomeric and enantiomeric purity of α‐tocopherol samples as the methyl ethers. It was established for the first time that naturally occurring α‐tocopherol is essentially a single enantiomer (2 R, 4′ R, 8′ R), synthetic all‐rac‐α‐tocopherol an equimolar mixture of four racemates, and that natural (E)‐(7 R, 11 R)‐phytol is diastereoisomerically and enantiomerically homogeneous.

Condensation of l-arylsulfcmyl-2-methyl-4-hydroxy-2-butenes (1) with 1-chloroand l-bromo-3-methyl-5-(2,6,6-trimethylcyclohexen-l-yl)-penta-2,4-diene (2) to afford 1-hydroxy-3,7-dimethyl-4-arylsulfonyl-9-(2,6,6-trimethylcyclohexen-l-yl) nona-2,6,8-triene (3) and the subsequent elimination of sulfinic acid from 3 to give vitamin A alcohol has been studied. An efficient and stereoselective synthesis of halide 2 from vinyl-d-ionol (14) using HX in ether at low temperature has been achieved. The use of diethyl-and disilylamides with the p-tolyl sulfone compound lb and bromide 2b gave 3b in 83-84% isolated yield. Sodamide-ammonia-terf-butyl alcohol effected elimination of sulfinic acid in 3b to afford, after acetylation, vitamin A acetate in 75% yield from 3b. In a through process, crystalline, all-trans vitamin A acetate was obtained in 67-68 and 72-73% yield based on 14 and lb, respectively.

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