Synthesis of C2-symmetric guanidino-sugars as potent inhibitors of glycosidases.

A series of enantiomerically pure C2-Symmetric guanidino-sugars was synthesized from D-mannitol. The first method described involves direct opening of a bis-epoxide by guanidine, whereas the second one deals with a mercury-catalyzed transformation of a cyclic thiourea into a N,N',N"-trisubstituted guanidine as a key step. The biological activity of these compounds towards several glycosidases has been evaluated. One of them (5) was found to selectively inhibit alpha-L-fucosidase of bovin kidney (2.8 microM).