[OH:1][C:2]1[C:3](=[O:17])[NH:4][C:5](=[O:16])[N:6]([CH:15]=1)[C@@H:7]1[O:14][C@H:11]([CH2:12][OH:13])[C@@H:9]([OH:10])[CH2:8]1.[OH-].[Na+].[CH2:20](Br)[CH3:21]>CO.O>[CH2:20]([O:1][C:2]1[C:3](=[O:17])[NH:4][C:5](=[O:16])[N:6]([CH:15]=1)[C@@H:7]1[O:14][C@H:11]([CH2:12][OH:13])[C@@H:9]([OH:10])[CH2:8]1)[CH3:21]The 2'-deoxy-5-hydroxyuridine (244 mg.,1mmol) was suspended in a mixture of methanol (10ml) and water (5ml) at room temperature, and 1 ml of 1.0N sodium hydroxide solution (1mmol) was added to generate the monoanion. Ethyl bromide (0.312ml, 4mmol) was added, and the reaction mixture was stirred for 16 hours. The solvent was removed in vacuo, and ethanol was added to and evaporated from the residue. The desired 5-ethoxy product was separated from small amounts of the 3 ethyl-5-ethoxy dialkyl byproduct by chromatography on a silica gel column using chloroform-methanol (9:1, v/v) as the solvent. Following crystallization from absolute ethanol, 5-ethoxy-2'-deoxyuridine was obtained in 52% yield (140 mg); mp 179°-181° C.; 1H NMR (methyl sulfoxide-d6),δ11.38 (1H, br s, NH), 7.58 (1H, s, H-6), 6.18 (1H, t, H-1'), 5.19 (1H, d, 3'-OH), 5.09 (1H, t, 5'-OH), 4.25 (1H, m, H-3'), 3.79 (3H, m. H4'and OCH2CH3 ), 3.59 (2H, br s,H-5'and H-5"), 2.10 (2H, m, H-2'and H-2") and 1.23ppm (3H, t, OCH2CH3). Anal. Calcd. for C11H16N2O6C, 48.53; H, 5.92; N, 10.29. Found: C, 48.69; H, 6.0-1; N, 10.36.
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