Synergistic solvent effect in 1,2-cis-glycoside formation

Construction of three continuous 1,2-cis-alpha-glucosidic linkages was achieved in optimized solvent system. High-throughput optimization was conducted, by using substrates protected by perdeuterated benzyl (Bn-d(7)) groups. It enabled facile evaluation of yield and stereoselectivity with H-1 NMR and MALDI-TOF MS, respectively. We found that CHCl3 and ethereal solvent had a synergetic effect to enhance the a-selectivity. The optimized solvent systems in CHCl3/CPME and CHCl3/Et2O were applied to the linear synthesis of Glc alpha 1-2Glc alpha 1-3Glc alpha l-3Man (GlC(3)Man(1)), which was achieved in 86% overall stereo selectivity. (c) 2007 Elsevier Ltd. All rights reserved.