To a solution of methyl2-[(cyclopentylamino)methyl]-2-ethyl-butanoate (Intermediate 252; 7.1 g, 31.3 mmol) in acetone (150 mL) was added potassium carbonate (5.3 g, 38.0 mmol) followed by 2,4-dichloro-5-nitropyrimidine (Aldrich; 6.1 g, 31.3 mmol). The black mixture was stirred at room temperature for 18 hours. The reaction was filtered and the solvent removed in vacuo to yield a black gum, which was dissolved in acetic acid (175 mL) and iron (7.0 g, 125 mmol) added and the reaction heated at 80° C. overnight. The resulting solution was filtered and the solvent removed in vacuo, the black solid/gum was quenched with water (75 mL) and to this was added sodium carbonate until basic, the resultant black emulsion was filtered through a pad of celite. The obtained mixture was extracted with DCM (3×150 mL), dried and the solvent removed in vacuo to yield a black solid. This was passed through a bond elute column (50 g) eluting with 0-1% MeOH in DCM to afford a brown solid, which was triturated with diethyl ether to yield the title compound as a white solid (3.05 g, 30%)
