General procedure for the synthesis of 2,3,5-tribenzyloxy-D-arabinofuranous acid-1,4-lactone from 2,3,5-tri-O-(phenylmethyl)-D-ribofuranose: Compound 30a (prepared according to J. Org. Chem., 1961, 26, 4605; 10.0 g, 23.8 mmol) was dissolved in anhydrous DMSO (30 mL) and stirred under nitrogen protection. Acetic anhydride (20 mL) was then added and the reaction mixture was stirred continuously for 48 h at room temperature. After the completion of the reaction was monitored by LC/MS, the reaction mixture was slowly poured into ice water (500 mL) and stirring was continued for 20 min. The aqueous phase was extracted with ethyl acetate (3 × 200 mL), and the organic phase was combined and washed with deionized water (3 × 200 mL). The aqueous phase was discarded and the organic phase was dried over anhydrous MgSO4 and concentrated to dryness under reduced pressure. The residue was dissolved in dichloromethane (DCM) and purified by silica gel column chromatography using 25% ethyl acetate/hexane as eluent to give the target product 30b in 96% yield.1H-NMR (CD3CN) data: δ 3.63-3.75 (m, 2H), 4.27 (d, 1H), 4.50-4.57 (m, 3H), and 4.65 (s, 3H), 4.69-4.80 (m, 2H), 7.25 (d, 2H), 7.39 (m, 13H).
