A convenient and asymmetric protocol for the synthesis of natural productscontaining chiral alkyl chains via Zr-catalyzed asymmetric carboalumination of alkenes. Synthesis of phytol and vitamins E and K

[GRAPHICS] A convenient and asymmetric protocol for the synthesis of chiral oligoisopr enoids is described. Typically, a C-14 vitamin E side chain 5 was synthesiz ed 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, ph ytol and vitamin K were synthesized in 21% and 28% overall yields, respecti vely, over five steps from 1.