| Abstract: | 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. |
