HIGH PI-FACE SELECTIVITY IN ANTIALDOL 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 alko xymethyl 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 con cise and highly stereocontrolled synthesis of the C24-C32 subunit 9 of , rapamycin (10).