Scheme 2
The scope of nitriles and saccharidesa. (a) The reaction was performed at 0.5 mmol scale using saccharide and trifluoromethanesulfonic acid (3 eq) at 40 °C in anhydrous DCM for 30 min. Then, nitrile (1 eq) was added, and the mixture was stirred under a nitrogen atmosphere for 2 h; (b) HPLC yields; (c) The d.e. values were calculated based on the separated yields of main products and their diastereomers. (d) N.P. no product was found; (e) N.D. the isomer of fucose-type products could not be separated by HPLC, N.S. no stereoselectivity. (f) A mixture of 3A (0.6 mg) and 3A’ (0.3 mg) was dissolved in methanol (1 ml). Then the mixture was separated using an Agilent Pursuit 5 μM, C18 250*4.6 mm column, and CHIRALCEL OD-RH 5 μM 4.6*150 mm column. The elution solvent consisted of water and methanol, the methanol concentration was increased from 5% to 95% over 30 min and subsequently maintained at 95% methanol for an additional 15 min.
