[NH2:1][C:2]1[N:10]=[C:9]2[C:5]([N:6]=[CH:7][N:8]2[CH2:11][CH2:12][CH:13]2[CH2:18][O:17]C(C)(C)[O:15][CH2:14]2)=[C:4]([NH2:21])[N:3]=1>C(O)(=O)C>[NH2:1][C:2]1[N:10]=[C:9]2[C:5]([N:6]=[CH:7][N:8]2[CH2:11][CH2:12][CH:13]([CH2:18][OH:17])[CH2:14][OH:15])=[C:4]([NH2:21])[N:3]=1A solution of 2,6-diamino-9-[2-(2,2-dimethyl-1,3-dioxan-5-yl)ethyl]purine (180 mg, 0.6 mmol) in 70% acetic acid (10 ml) was stirred for 1 hour at room temperature. The solvent was removed, the residue was suspended in methanol and sodium methoxide was added to neutralise. Column chromatography on silica gel eluting with chloroformmethanol mixtures (6:1, 4:1 and 3:1) gave 2,6-diamino-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (95 mg, 63%), m.p. 187°-190° C.; λmax (H2O, pH6.5) 215 (ε25,500), 255 (ε7,290), and 280 (ε9,170) nm; νmax 3150, 1680, 1650, 1605, 1590, and 1410 cm-1 ; δH [(CD3)2SO] 1.46 (1 H, m, CHCH2CH2), 1.73 (2 H, q, J 7.1 Hz, CHCH2CH2), 3.3-3.5 (4 H, ddd (ABX), JAB 10.6 Hz, JAX 5.5 Hz and JBX 5.9 Hz, 2×CH2O), 4.01 (2 H, t, J 7.3 Hz, CH2N), 4.41 (2 H, br, D2O exchangeable, 2×OH), 5.70 (2 H, s, D2O exchangeable, NH2), 6.56 (2 H, s, D2O exchangeable, NH2), and 7.69 (1 H, s, 8-H) (Found: C, 46.09; H, 6.32; N, 31.69%; C10H16N6O2 0.1CHCl3 requires C, 45.91; H, 6.14; N, 31.81%).
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