1,5-Acyclic stereoselection. The stereocontrolled synthesis of optically active vitamin E fourteen-carbon side chain alcohol

The Diels–Alder product 3 was first transformed into the symmetrical nine-membered cyclic carbonate 8. Reaction of 8 with l-(−)-α-methylbenzylamine (12) yielded a mixture of optically active diastereoisomeric urethanes 9a (9, R = H, R′ = C6H5CHCH3NHCO—) and 9b (9, R = C6H5CHCH3NHCO—, R′ = H) which were separated and respectively converted into 11a and 11b. Compounds 11a and 11b were then transformed respectively into the optically active side chain alcohol 2 (R = H) of vitamine E (1).