Efficient stereoselective synthesis of natural α-tocopherol (vitamin E)

Reduction by bakers' yeast of the aldehyde (1) gives 2-methyl-5-phenylpent-4-en-1-ol, containing ca. 87% of the (2S)-isomer (3), which is converted into (3R,7R)-3,7,11-trimethyldodecan-1-ol (8), a key intermediate in the synthesis of natural α-tocopherol (19); the same alcohol (8) and its lower homologue (16), which is also an intermediate in the same synthesis, are both obtained in optically pure form from the acid (9).