High ?-Face Selectivity in Anti Aldol Reactions of E-Enol Borinates from Chiral Alkoxymethyl Ketones: Stereocontrolled Synthesis of a C24-C32 Polyol Subunit of Rapamycin

Article abstract of DOI:10.1021/jo00068a002

Using (c-C6H11)2BCl/Et3N, the aldol reactions of the α-chiral alkoxymethyl ketones 5 and 6 with achiral aldehydes gives the 1,2-anti-2,4-anti adducts 7 and 8 in 83-95 percent yield with >/= 95 percent diastereoselectivity.This novel aldol reaction was applied to a concise and highly stereocontrolled synthesis of the C24-C32 subunit 9 of rapamycin (10).