Experimental (Try hovering over some of the words!)

(21): Alcohol 6 (180 mg,0.44 mmol) and

18 (321 mg, 0.57 mmol) were coevaporated with toluene (2 x 50 mL) and then, placed on high vacuum for 1 h.

The material was dissolved in CH2Cl2 (2.2mL) and cooled to 0 °C. Then, TMSOTf (7.9 mL, 0.044 mmol) dissolved in CH2Cl2 (0.05 mL)was added.

After stirring for 1 h at 0 °C, the reaction was quenched with

. The crude product was purified by silica chromatography (40:60 to 50:50 to 60:40 EtOAc/cyclohexane) to give the intermediate disaccharide (247 mg, 0.32 mmol) in 72% yield.

The disaccharide (10 mg, 0.013 mmol) was then dissolved in CH2Cl2 (0.64 mL) at 23 °C and treated sequentially with

, and N2H4•H2O (2.5 mL, 0.051 mmol).

After stirring for 3 h, the reaction was quenched with acetone (0.1 mL) and coevaporated with toluene (1 x 20 mL).

The crude residue was purified by

(40:60 to 50:50 to 60:40 EtOAc/hexanes) to furnish alcohol 21 (7.8 mg, 0.011mmol) in 89% yield.