A Convenient and Asymmetric Protocol for the Synthesis of Natural Products Containing Chiral Alkyl Chains via Zr-Catalyzed Asymmetric Carboalumination of Alkenes. Synthesis of Phytol and Vitamins E and K

[reaction: see text]. A convenient and asymmetric protocol for the synthesis of chiral oligoisoprenoids is described. Typically, a C14 vitamin E side chain 5 was synthesized in 47% yield over four steps. Isomeric purity of 5 was upgraded to >99% R at C-2 and 97% R at C-6 by the statistical formation of stereoisomeric p-phenylenebisurethanes and their diastereomeric separation. In addition, phytol and vitamin K were synthesized in 21% and 28% overall yields, respectively, over five steps from 1.