Synthesis of 5a,5a'-dicarba-d-glucobioses from conformationally restricted carbaglucosyl triflates using S N 2-type inversion with carbaglucosyl nucleophiles

Novel carbohydrate mimics were designed which contain two 5a-carba-d-glucose residues, one each at reducing and nonreducing end, and thus these mimics are 5a,5a'-dicarba-d-glucobioses. Dicarbadisaccharides have attractive features such as stability against endogenous degradative enzymes and being resistant to glycation reactions such as the Maillard reaction. For the synthesis of dicarba-β-d-isomaltose derivatives, the carbaglucosyl triflate locked in C conformation was synthesized by protecting with butane-2,3-diacetal group or benzylidene group. Then, 5a,5a'-dicarba-β-d-maltose and 5a,5a'-dicarba-α,β-d-trehalose were synthesized by the S 2-type inversion reaction using 4,6-O-benzylidene carbaglucosyl triflate with 4-OH and 1-OH carba-β-d-glucose derivatives, respectively, and similarly 5a,5a'-dicarba-α-d-isomaltose with 6-OH carba-α-d-glucose derivative.