Perfectly regioselective acylation of a cardiac glycoside, digitoxin, via catalytic amplification of the intrinsic reactivity

Organocatalytic regioselective acylation of digitoxin has been developed. This method provides the 4′′′-O-manoacylate as the sole product without the concomitant formation of diacylates. The extremely high regioselectivity was assumed to be the result from the combined effects of the high intrinsic reactivity of C(4′′′)–OH and catalyst-promoted regioselective acylation of the same hydroxy group.