To a mixture of 4-chloro-5-iodo-7H-pyrrolo[2,3-d]pyrimidine 8 (903 mg, 3.23 mmol), 2-C-methyl-1,2,3,5-tetra-O-benzoyl-β-D-ribofuranose 9 (1.7 g, 2.93 mmol) and DBU (1.3 ml, 8.69 mmol) in MeCN (20 ml) was dropwise added TMSOTf (2.1 ml, 11.62 mmol) at 0° C. and the mixture was then stirred at 70° C. for 22.5 h. After cooling, the mixture was diluted with AcOEt (100 ml), washed with aq NaHCO3 (sat., 25 ml), water (25 ml) and brine (25 ml). The organic layer was dried over MgSO4 and evaporated. The residue was chromatographed on silica (hexanes/toluene, 1:1; then hexanes/toluene/MeCN, 49:49:2→3:3:4) affording title compound 10 as a white foam (1.04 g, 48%). Compound was recrystallized from EtOH. Mp 95° C. [α]20D −69.3 (c 0.280, CHCl3). 1H NMR (500 MHz, CDCl3): 1.59 (s, 3H, CH3); 4.72 (td, 1H, J4′,3′=J4′,5′b=5.8, J4′,5′a=3.4, H-4′); 4.85 (dd, 1H, Jgem=12.2, J5′b,4′=5.8, H-5′b); 4.95 (dd, 1H, Jgem=12.2, J5′a,4′=3.4, H-5′a); 6.03 (d, 1H, J3′,4′=5.8, H-3′); 6.95 (s, 1H, H-1′); 7.34, 7.46 and 7.47 (3×m, 3×2H, H-m-Bz); 7.54, 7.59 and 7.61 (3×m, 3×1H, H-p-Bz); 7.69 (s, 1H, H-6); 7.96, 8.10 and 8.11 (3×m, 3×2H, H-o-Bz); 8.75 (s, 1H, H-2). 13C NMR (125.7 MHz, CDCl3): 17.92 (CH3); 52.68 (C-5); 63.33 (CH2-5′); 75.55 (CH-3′); 80.04 (CH-4′); 84.93 (C-2′); 88.95 (CH-1′); 117.71 (C-4a); 128.49, 128.54 and 128.63 (CH-m-Bz); 128.65, 129.50 and 129.61 (C-i-Bz); 129.78, 129.83 and 129.92 (CH-o-Bz); 132.66 (CH-6); 133.38, 133.66, 133.72 (CH-p-Bz); 150.68 (C-7a); 151.17 (CH-2); 153.15 (C-4); 165.09, 165.33 and 166.32 (CO). IR (CHCl3): 3092, 3066, 3034, 1727, 1602, 1587, 1577, 1538, 1504, 1493, 1451, 1444, 1339, 1316, 1269, 1248, 1178, 1162, 1141, 1116, 1070, 1027, 1002, 952, 943, 843, 822, 725, 712, 686, 617, 600. MS (FAB): m/z 738 (M+H). HRMS (FAB) for C33H26ClIN3O7 [M+H] calcd: 738.0504. found: 738.0491. Anal. Calcd for C33H25ClIN3O7: C, 53.71; H, 3.41; N, 5.69. Found: C, 53.91; H, 3.29; N, 5.38.
