Enantioselective synthesis of apoptolidin sugars.

[structure: see text] The de novo synthesis of the C9 and C27 sugar subunits (2) and (3), respectively, of the potent antitumor agent, apoptolidin, has been accomplished. A titanium tetrachloride-mediated asymmetric anti glycolate aldol addition was utilized to establish the 4' and 5' stereogenic centers of each of the three monosaccharides. Elaboration of the aldol adducts efficiently provided the three sugar units. A beta-selective glycosidation completed the construction of the C27 disaccharide.