A mixture of 4-methylaminomethyl-2-phenyl-1,3-dioxane (0.368 g, 1.775 mmol), 9-deazahypoxanthine (0.288 g, 2.131 mmol), acetic acid (0.508 ml, 8.88 mmol) and 37% aq formaldehyde (0.264 ml, 3.55 mmol) in dioxane (10 mL) was stirred and heated in stoppered flask at 80° C. More 37% aq formaldehyde (0.132 ml, 1.775 mmol) was added and the stoppered flask was heated again at 80° C. for ˜24 h. The solution was concentrated to dryness and chromatography (10% 7M NH3/MeOH in CH2Cl2) separated the less polar byproducts, but the product and deazahypoxanthine eluted together. Chromatography of this material eluting with CHCl3/EtOAc/MeOH 5:2:1, then 4:2:3 followed by 20% 7M NH3/MeOH, gave the title compound as a white solid (0.406 g, 1.146 mmol, 64.5% yield). 1H NMR (CDCl3/CD3OD) δ 7.84 ((1H, s), 7.48-7.45 (2H, m), 7.39 (1H, s), 7.37-7.28 (3H, m), 5.56 (1H, s), 4.30-4.11 (2H, m), 4.02 (1H, dt, J=11.9, 2.5 Hz), 3.91 and 3.83 (1H each, d, J=13.8 Hz), 2.73 (1H, dd, J=13.5, 7.5 Hz), 2.57 (1H, dd, J=13.5, 3.4 Hz), 2.39 (3H, s), 1.74 (ddd, J=12.5, 4.9 Hz), 1.53 (1H, d, J=12.4 Hz); 13C NMR δ 156.8, 146.2, 143.2, 140.6, 130.6, 130.5, 129.8, 128.0, 119.7, 113.9, 103.0, 77.4, 68.7, 62.5, 52.0, 44.3, 31.5.
