Reaction Steps
(1S,3R,4R,7S)-7-Benzyloxy-1-methanesulfonyloxymethyl-3-(6-N-benzoyl-adenine-9-yl)-2,5-dioxabicyclo-[2.2.1]heptane (5D) (11.5 g.; 20.8 mmol) was dissolved in anh. DMF (450 mL). Sodium benzoate (5.40 g.; 37.4 mmol) was added and the mixture was heated to 90° C. for 7 h. The solution was cooled to rt., filtered, evaporated and coevaporated with AcCN. The residue was redissolved in dichloromethane (150 mL) and a saturated aqueous solution of NaHCO3 (150 mL) was added. The phases were separated and the organic phase was washed with a saturated aqueous solution of NaHCO3 (2×100 mL) and brine (100 mL), dried (Na2SO4) and evaporated to give 12.5 g. of a yellowish solid. Recrystallization from EtOH:H2O (1250 mL; 1:1 v/v) gave 28 in 88% yield (10.63 g.). δH (DMSO-d6): 11.2 (1H, br s), 8.72 (1H, s), 8.48 (1H, s), 8.06 (2H, m), 7.94 (2H, m), 7.66 (2H, m), 7.54 (4H, m), 7.36-7.26 (5H, m), 6.11 (1H, s), 4.97 (1H, s), 4.82 (2H, s), 4.77 (1H, s), 4.75 (1H, d, J=12.4 Hz), 4.69 (1H, d, J=11.9 Hz), 4.19 (1H, d, J=8.0 Hz), 4.07 (1H, d, J=7.9 Hz). δc (DMSO-d6): 165.3, 150.5, 141.9, 137.7, 133.7, 132.5, 129.3, 129.1, 128.9, 128.6, 128.5, 128.3, 127.7, 127.6, 125.7, 85.9, 85.3, 77.9, 77.1, 72.0, 71.3, 60.6.
