EX-1A) A solution of 1-benzyl-5-nitro-2,4(1H,3H) pyrimidinedione (6.14 g, 24.82 mmol) prepared as described by Vampa, G. and Pecorari P. Boll. Chim. Farm. 1987,126, 467–469 was dissolved in 100 mL dimethylsulfoxide and potassium dicarbonate (3.78 g, 27.34 mmol) was added in one portion with stirring. After approximately 10 minutes a solution of methyl bromoacetate (2.50 mL, 26.40 mmol) in 20 mL dimethylsulfoxide was added drop wise over a 10 minute period. The reaction mixture was then heated to 40° C. and allowed to stir for 18 hours. The reaction mixture was diluted with water (500 mL). The aqueous solution was extracted with ethyl acetate (4×100 mL). The combined organic solutions were washed with water (1×150 mL), brine (2×150 mL). The organic solution was dried (MgSO4), filtered, and concentrated to give an oil. The crude oil was purified by MPLC (20% ethyl acetate/hexanes) to give pure 1-Benzyl-3-methoxycarbonyl-methyl-5-nitro-2,4(1H,3H)pyrimidinedione (EX-1A) as a white solid in 81% yield: 1H NMR (400 MHz, CDCl3) δ 8.73 (s, 1H) 7.38–7.30 (m, 5H), 5.06 (s, 2H), 4.69 (s, 2H), 3.72 (s, 3H); HRMS (ES) calcd for C14H13N3O6 319.0804, found 319.0797.
