Example 9 l-(2-Isopropoxyethyl)-2-thioxo-l,2,3,5-tetrahydro-pyrrolo[3,2-d]pyrimidin-4-one (a) 3-[(2-Isopropoxyethyl)ωnino]-lH-pyrwle-2-carboxylic acid ethyl ester Trichlorocyanuric acid (1.84 g, 7.93 mmol) was added to a solution of 2- isopropoxyethanol (0.75 g, 7.21 mmol) in CH₂Cl₂ (3 mL). The reaction mixture was cooled to 0 °C and TEMPO (0.022 g, 0.14 mmol) was carefully added in small portions. The mixture was stirred at r.t. for 20 minutes then filtered through Celite and washed with CH₂Cl₂. The filtrate was kept cold, 0 °C, during filtration. The aldehyde solution was added to a stirred mixture of 3-amino-lH-pyrrole-2-carboxylic acid ester (0.83 g, 5.41 mmol) and HOAc (0.62 mL, 10.8 mmol) at 0 °C in methanol (5 mL). The mixture was stirred for 20 minutes, then NaCNBH₃ (0.34 g, 5.41 mmol) was added. After stirring at r.t for 2 h, the solution was evaporated onto silica and purified by flash column chromatography (heptane/ethyl acetate gradient; 0 to 100% ethyl acetate) to yield the title compound (0.75 g, 58%) as an oil. ¹H NMR (DMSO-d₆) δ ppm 10.72 (IH, br s), 6.76-6.74 (IH, m), 5.66-5.65 (IH, m), 5.34(1H, br s), 4.17 (2H, q, J=7.0 Hz), 3.59-3.49 (3H, m), 3.15 (2H, q, J=5.6 Hz), 1.26 (3H, t, J=7.0 Hz), 1.10 (3H, s), 1.08 (3H, s); MS (ESI) m/z 241 (M +1).

(b) l-(2-Isopropoxyethyl)-2-thioxo-l,2,3,5-tetrahydro-pyrrolo[3,2-d]pyrimidin-4-one The title compound (0.17 g, 23%) was prepared in accordance with the general method B using 3-[(2-isopropoxyethyl)amino]-lH-pyrrole-2-carboxylic acid ethyl ester (0.7 g, 2.91 mmol) and ethoxycarbonyl isothiocyanate (0.40 mL, 3.50 mmol).

¹H NMR (DMSO-d₆) δ ppm 12.74 (2H, br s), 7.35 (IH, d, J=2.8 Hz), 6.29 (IH, d, J=3.0

Hz), 4.49 (2H, t, J=6.3 Hz), 3.72 (2H, t, J=6.3 Hz), 3.60-3.58 (IH, m), 1.02 (3H, s), 1.01 (3H, s);

MS (ESI) m/z 254 (M +1).