D-ribose (1; 20.0 g, 133.2 mmol) was suspended in a solvent mixture of acetone (100 mL) and methanol (100 mL) at room temperature. Concentrated sulfuric acid (10 mL) was slowly added and the reaction mixture was stirred for 48 hours. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, solid sodium bicarbonate (NaHCO3) was added to neutralize the reaction solution. The insoluble solids were removed by filtration and the filtrate was subsequently concentrated. The concentrated mixture was extracted with ethyl acetate (EtOAc). The organic layers were combined, dried with anhydrous magnesium sulfate (MgSO4), filtered and the solvent was evaporated to remove the organic solvent. The crude product was purified by silica gel fast column chromatography using hexane/ethyl acetate (5:1, v/v) as eluent to afford the target compound ((3aR,4R,6R,6aR)-6-methoxy-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxin-4-yl)methanol as a light yellow oil in 24.4 g (90% yield). The Rf value of the product was 0.2 (eluent: hexane/EtOAc = 5:1, v/v). The specific optical rotation [α]D25 was -80.00 (c 1.00, CHCl3), which is in accordance with the literature value [α]D20 -75.00 (c 1.00, CHCl3).1H NMR (CDCl3, 400 MHz) data were as follows: δ= 4.97 (s, 1H), 4.83 (d, J = 5.7Hz, 1H), 4.58 (d, J = 6.0 Hz, 1H), 4.42 (t, J = 2.7 Hz, 1H), 3.56-3.72 (m, 2H), 3.43 (s, 3H), 3.32 (dd, J = 10.0,3.0 Hz, 1H), 1.49 (s, 3H), 1.32 (s, 3H).
