Tri-butyltin hydride (0.18 mL, 0.67 mmol), followed by a 1M solution of triethyl borane in hexanes (0.5 mL, 0.5 mmol) were added under argon to a suspension of 5'-O-(t-butyldiphenylsilyl)-3'-deoxy-2'-phenylselenenylthymidine 6 (0.282 g, 0.45 mmol) in anhydrous benzene. The reaction mixture slowly became clear. After 4 hours of stirring, thin layer chromatography (CH2Cl2 /MeOH: 9.5/0.5) indicated complete disappearance of the starting material. The reaction mixture was diluted with acetonitrile then was concentrated to a thick syrup. The syrup was chromatographed through a column of silica gel (230-400 mesh), eluting first with dichloromethane, followed by 3% methanol in dichloromethane. Compound 10 was isolated as a foamy solid. Yield 0.186 g, 89%. 1H NMR (CDCl3, 90 MHz): δ 1.10 (s, 9 H, t-Bu); 1.65 (d, 3 H, 5-CH3, J=1.1 Hz); 1.9-2.4 (m, 4 H, 2' and 3'-H); 3.7-4.3 (m, 3 H, 4' and 5'-H); 6.11 (pseudo t, 1 H, 1'-H, J=4 Hz); 7.26 (s, 1 H, 6-H); 7.4-7.9 (m, 10 H, Ar-H); 8.32 (br s, 1 H, NH). Anal. Calcd for C26H32N2O4 : C, 67.21; H, 6.94; N, 6.03. Found: C, 67.09; H, 6.96; N, 6.01.
