HIGH PI-FACE SELECTIVITY IN ANTI-ALDOL REACTIONS OF E-ENOL BORINATES FROM CHIRAL ALKOXYMETHYL KETONES - STEREOCONTROLLED SYNTHESIS OF A C24-C32 POLYOL SUBUNIT OF RAPAMYCIN

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