β-sitosterol (124.4 g, 0.3 mol) and D-glucose (18.0 g, 0.1 mol) were dissolved in ethylbenzene (600 mL). Trimethylsilyl trifluoromethanesulfonate (TMSOTf, 8.9 g, 7.3 mL, 40 mmol) was slowly added to the reaction system at 80 °C and the reaction was continued at a constant temperature until thin-layer chromatography (TLC) detection showed that the D-glucose was almost completely consumed (about 15 h). Upon completion of the reaction, the reaction solution was concentrated and subsequently separated by silica gel column chromatography using dichloromethane as eluent (silica gel particle size 100-200 mesh). The separation was monitored by TLC until β-sitosterol was no longer detected in the eluate, and the corresponding eluate was collected and concentrated to give the recovered β-sitosterol (83.0 g, 0.2 mol). The elution was continued with ethyl acetate as eluent and monitored by TLC until the target product (2R,3R,4S,5S,6R)-2-((3S,8S,9S,10R,13R,14S,17R)-17-((2R,5R)-5-ethyl-6-methylheptan-2-yl)-10,13-dimethyl-2,3, 4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl)oxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol. Concentration of the eluate containing the target product gave a white solid product (47.3 g) in 82% yield and 97.8% purity as determined by high performance liquid chromatography (HPLC).
