Novel "Reverse Kahne-type glycosylation": Access to O-, N-, and C-linked epipodophyllotoxin conjugates

Exposure of epipodophyllotoxin C-4-sulfoxides to triflic anhydride, followe d by a silyl glycoside, provides a glycoconjugate of the etoposide variety via formal "reverse Kahne glycosylation," To our knowledge, this is the fir st example of this variant of the Kahne activation method wherein the activ ating functionality is positioned on the aglycon, rather than on the sugar. Phenols, anilines, or allyl silanes are also efficiently captured at C-4, producing the corresponding O-, N, and C linked lignan conjugates.