Reaction SMILES: [NH2:1][C:2]1[N:10]=[C:9]2[C:5]([N:6]=[CH:7][N:8]2[C@@H:11]2[O:17][C@H:16]([CH2:18][OH:19])[C@@H:14]([OH:15])[C@@H:12]2[OH:13])=[C:4]([O:20][CH3:21])[N:3]=1.[C:22](OCC(Cl)(Cl)Cl)(=[O:25])[CH2:23]C.C(OCC(Cl)(Cl)Cl)(=O)C.ClC(Cl)(Cl)CO.C(Cl)(=O)C>N1C=CC=CC=1.P([O-])([O-])([O-])=O.[K+].[K+].[K+].O>[NH2:1][C:2]1[N:10]=[C:9]2[C:5]([N:6]=[CH:7][N:8]2[C@@H:11]2[O:17][C@H:16]([CH2:18][O:19][C:22](=[O:25])[CH3:23])[C@@H:14]([OH:15])[C@@H:12]2[OH:13])=[C:4]([O:20][CH3:21])[N:3]=1
Reactant: CCC(=O)OCC(Cl)(Cl)Cl
Reactant: COc1nc(N)nc2c1ncn2[C@@H]1O[C@H](CO)[C@@H](O)[C@@H]1O
Agent: CC(=O)OCC(Cl)(Cl)Cl
Agent: O=P([O-])([O-])[O-]
Agent: OCC(Cl)(Cl)Cl
Solvent: CC(=O)Cl
Solvent: c1ccncc1
Solvent: O
Product: COc1nc(N)nc2c1ncn2[C@@H]1O[C@H](COC(C)=O)[C@@H](O)[C@@H]1O

Procedure:
2-Amino-6-methoxy-9-b-D-arabinofuranosyl-9H-purine (1.0 g, 3.3 mmol) was suspended in 40 ml of pyridine that contained 300 μL of H2O and 1 ml of trichloroethyl propionate (Trichloroethyl acetate was synthesized as follows:2,2,2-trichloroethanol (19.1 mL, 197.1 mmole) and dry pyridine (40 mL) were placed in a three-neck, round-bottom flask equipped with argon inlet valve, thermometer, dropping funnel, magnetic stirring, and ice/H2O bath. Acetyl chloride (14.5 mL, 199.8 mmole) was placed in the dropping funnel and added over a ten minute period, keeping the temperature below 25° C. while stirring under argon. The resulting product was washed with H2O (2×100 mL), 5% NaHCO3 (2×100 mL), and H2O (2×100 mL). The organic layer was dried over MgSO4, then filtered through Whatman #1 paper, and distilled under vacuum. A middle cut of 5.18 g was the desired material, contaminated with a small amount of acetic acid: 1H-NMR (CDCl3): δ4.73 (s, 2H, CH2O), 2.20 (s, 3H, CH3CO); MS (Cl, CH4): m/z 197 (M+H, C4H5O237Cl3), 195 (M+H, C4H5O237Cl235Cl), 193 (M+H, C4H5O2O35Cl237Cl), 191 (M+H, C4H5O235Cl3), 159 (195-HCl, C4H4O237Cl2), 157 (193-HCl, C4H4O237Cl35Cl), 155 (191-HCl, C4H4O235Cl2); (El): m/z 195 (M+H), 193 (M+H), 191 (M+H), 157 (193-HCl), 155 (191-HCl). Analysis for C4H5Cl3O2 +0.054 mole CH3COOH: C, 25.35; H, 2.70; CI, 54.62. Found: C, 25.57; H, 2.72; Cl, 54.66.). The reaction was initiated with 0.050 g of subtilisin (Sigma Chemical Co., St. Louis, Mo., P-5380, lot#38F-0356,), which had been activated by dissolving 1 g of the enzyme in 20 ml of 0.1M potassium phosphate at pH 7.8 and lyophilizing to dryness. After stirring for 23 hours at 40° C. an additional 50 mg of subtilisin and 2 mL of trichloroethyl acetate were added to the reaction. After stirring at 40° for an additional 24 hours the reaction was quenched by filtering off the enzyme and the solvent was removed in vacuo. The crude product was purified by chromatography on a 4.5×25 cm silica gel column with CH2Cl2 :CH3OH (9:1) as eluant. Product fractions were pooled and lyophilized from water to yield 0.28 g of the desired product as a white powder. TLC Rf =0.35 (silica gel; CH2Cl2 :CH3OH (9:1)); UV λmax (ε, mM-1 cm-1) at pH 7.0, 279 nm (8.8). 1H-NMR(200 MHz, DMSO-d6): δ7.83 (s, 1H, H8), 6.45 (s, 2H, 2-NH2), 6.14(d, 1H, J=3.7 Hz, H1'), 5.75 (d, 1H, J=4.5 Hz, 2'--OH), 5.65 (d, 1H, J=3.7 Hz, 3'--OH), 4.26(m, 2H, H2' and H3'), 4.07 (m, 2H, H5') 3.94 (s, 3H, --OCH3) 3.92 (m, 1H, H4'), 2.01 (s, 3H, CH3CO2--); MS (Cl) 340 (M+1), 280 (M--CH3CO2). Anal. Calcd. for C14H19N5O6.0.52 H2O: Calcd: C, 44.77; H, 5.22; N, 20.12. Found: C, 44.79; H, 5.21; N, 20.09.