Example 26 Synthesis of ethyl 9-carboxymethyladenine: Adenine (10 g, 74 mmol) and potassium carbonate (10.29 g, 74 mmol) were suspended in N,N-dimethylformamide (DMF) followed by the addition of ethyl bromoacetate (8.24 mL, 74 mmol). The reaction mixture was stirred at room temperature and under nitrogen protection for 2.5 h. After completion of the reaction, it was filtered. The solid residue was washed three times with DMF (10 mL). All filtrates were combined and the solvent was removed by distillation under reduced pressure to give a yellow-orange solid. To this solid, water (200 mL) was added and the pH was adjusted to 6 with 4 N hydrochloric acid. after stirring for 10 min at 0 °C, the precipitate was collected, washed with water and purified by recrystallization in 96% ethanol (150 mL). Isolation by filtration gave N-ethyl acetate adenopyrimidine and the product was washed thoroughly with ether. The final yield was 3.4 g (20% yield) with a melting point of 215.5-220°C. Elemental analysis results (C9H11N5O2 calculated/measured values): C: 48.65/48.86; H: 4.91/5.01; N: 31.42/31.66. Nuclear magnetic resonance hydrogen spectrum (250 MHz, DMSO-d6): δ 7.25 (broad single peak, 2H, NH), 5.06 (single peak, 2H, NCH2), 4.17 (quadruple peak , 2H, J=7.11Hz, OCH2), 1.21 (triple peak, 3H, J=7.13Hz, CH3). NMR carbon spectrum showed major peaks located at 152.70, 141.30, 61.41, 43.97 and 14.07 ppm. fast atom bombardment mass spectrometry (FAB-MS) showed molecular ion peak m/z 222 (MH+). IR spectra (cm-1, intensity): 3855 (54.3), 3274 (10.4), 3246 (14.0), 3117 (5.3), 2989 (22.3), 2940 (33.9), 2876 (43.4), 2753 (49.0), 2346 (56.1), 2106 (57.1), 1899 ( 55.7), 1762 (14.2), 1742 (14.2), 1671 (1.8), 1644 (10.9), 1606 (0.6), 1582 (7.1), 1522 (43.8), 1477 (7.2), 1445 (35.8), 1422 (8.6).
