The Journal of Organic Chemistry product was purified by flash chromatography (hexanes/EtOAc, 2:1, Rf 0.56 for hexanes/EtOAc, 1:1) to give diacetate α-18 (0.074 g, 90%): mp 134 135 C (CHCl3/i-Pr2O); [α]2D0 41.49 (c 0.4, acetone); IR (Si) νmax 2932, 2859, 1753, 1539, 1478, 1367, 1233, 1105 cm 1; 1H NMR (400.1 MHz, CDCl3) δ 7.70 7.65 (m, 4H), 7.46 7.36 (m, 7H), 7.16 (d, J = 1.3 Hz, 1H), 6.88 (d, J = 5.8 Hz, 1H), 6.05 (dd ≈ t, J = 5.7 Hz, 1H), 5.53 (dd, J = 5.3, 1.8 Hz, 1H), 4.54 (ddd ≈ q, J = 2.1 Hz, 1H), 3.84 (AB system, J = 11.6, 2.6, 2.3 Hz, 2H), 1.89 (s, 3H), 1.84 (s, 3H), 1.10 (s, 9H); 13C NMR (100.6 MHz, CDCl3) δ 169.3, 168.2, 144.7, 135.5 (2C), 135.5 (2C), 132.2 (2C), 130.1, 130.0, 127.91 (2C), 127.90 (2C), 127.5, 122.4, 87.5, 85.6, 71.8, 71.1, 63.9, 26.7 (3C), 20.3, 19.7, 19.0. Anal. Calcd for C28H33N3O8Si: C, 59.24; H, 5.86; N, 7.40. Found: C, 59.33; H, 5.59; N, 7.42. 1-α-(20,30-Di-O-acetyl-D-ribofuranosyl)-2-nitroimidazole (α-26). Nucleoside α-18 (0.194 g, 0.342 mmol) was desilylated by general procedure B. The residue was purified by flash chromatography (hexanes/EtOAc, 1:1, Rf 0.10) to give α-26 (0.102 g, 91%) as an oil: [α]2D0 47.54 (c 1.3, acetone); IR (Si) νmax 3385, 1751, 1541, 1482, 1367, 1240, 1161, 1104 cm 1 1 ; H NMR (400.1 MHz, CDCl3) δ 7.39 (d, J = 1.1 Hz, 1H), 7.17 (d, J = 1.1 Hz, 1H), 6.90 (d, J = 5.5 Hz, 1H), 5.87 (t, J = 5.5 Hz, 1H), 5.26 (dd, J = 5.5, 2.8 Hz, 1H), 4.56 (q, J = 2.8 Hz, 1H), 3.87 (AB system, J = 12.1, 2 2.8 Hz, 2H), 2.55 (br s, 1H), 1.92 (s, 3H), 1.83 (s, 3H); 13C NMR (100.6 MHz, CDCl3) δ 169.6, 168.5, 144.6, 127.6, 122.5, 87.6, 85.2, 71.2, 71.0, 62.0, 20.3, 19.8. Anal. Calcd for C12H15N3O8: C, 43.77; H, 4.59; N, 12.76. Found: C, 43.43; H, 4.26; N, 12.17. 1-α-[20,30-Di-O-acetyl-50-O-(4-toluenesulfonyl)-D-ribofu- ranosyl]-2-nitroimidazole (α-27). 4-Toluenesulfonyl chloride (0.136 g, 0.693 mmol, 3 equiv) was dissolved in a solution of alcohol α-26 (0.076 g, 0.231 mmol) in dry pyridine (1.26 mL). The reaction mixture was kept for 18 h at 4 C (no starting material; TLC, hexanes/EtOAc, 1:2) and then quenched by adding water (10 mL) and 2 M HCl (10 mL). The mixture was extracted with EtOAc (3 10 mL). The combined organic layers were washed with saturated aq NaHCO3 (10 mL) and water (10 mL), dried (Na2SO4), and concentrated under reduced pressure. The residue was purified by flash chromatography (hexanes/EtOAc, 1:1, Rf 0.31 for hex- anes/EtOAc, 1:2) to give tosylate α-27 (0.084 g, 75%): mp 119 120 C (CHCl3/i-Pr2O); [α]2D0 18.87 (c 0.8, acetone); IR (Si) νmax 1756, 1539 1480, 1367, 1234, 1178 cm 1 1 ; H NMR (400.1 MHz, CDCl3) δ 7.81 (d, J = 8.3 Hz, 2H), 7.35 (d, J = 8.3 Hz, 2H), 7.29 (s, 1H), 7.14 (s, 1H), 6.62 (d, J = 5.3 Hz, 1H), 5.68 (t, J = 5.3 Hz, 1H), 5.28 (dd, J = 5.3, 3.7 Hz, 1H), 4.62 (ddd ≈ q, J = 3.5 Hz, 1H), 4.30 (AB system, J = 11.6, 3.5, 3.0 Hz, 2H), 2.42 (s, 3H), 1.90 (s, 3H), 1.82 (s, 3H); 13C NMR (100.6 MHz, CDCl3) δ 169.1, 168.0, 145.7, 144.5, 132.3, 130.1 (2C), 127.9 (2C), 127.8, 122.2, 87.5, 81.6, 70.5, 70.4, 68.0, 21.6, 20.2, 19.7. Anal. Calcd. for C19H21N3O10S: C, 47.20; H, 4.38; N, 8.69. Found: C, 46.93; H, 4.14; N, 8.50. ’ ASSOCIATED CONTENT bS Supporting Information. NMR spectra of selected com- pounds. 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