C(O[C:4](=[O:14])[C:5]([NH:7][CH2:8][C:9]([O:11][CH2:12][CH3:13])=[O:10])=[O:6])C.[CH3:15][O:16][CH:17]([O:20][CH3:21])[CH2:18][NH2:19]>CC(O)C>[CH3:13][CH2:12][O:11][C:9]([CH2:8][NH:7][C:5]([C:4]([NH:19][CH2:18][CH:17]([O:20][CH3:21])[O:16][CH3:15])=[O:14])=[O:6])=[O:10]To a solution of N-ethoxycarbonylmethyl-oxalamic acid ethyl ester (84.0 g, 414 mmol) 2–1 in 2-propanol (500 mL) was added aminoacetaldehyde dimethyl acetal (45.7 g, 435 mmol) in one portion. After stirring overnight at room temperature, the reaction mixture was concentrated to a thick orange oil. This thick slurry was diluted with 2-propanol (300 mL) and the solid was broken up with a spatula. Filtration afforded a solid which was further rinsed with an additional portion of 2-propanol. Removal of residual 2-propanol was accomplished via high vacuum to afford a light orange solid: 1H NMR (CDCl3) δ 7.82 (br s, 1H), 7.50 (br s, 1H), 4.41 (t, 1H, 5.3 Hz), 4.24 (q, 2H, 7.1 Hz), 4.09 (d, 2H, 5.9 Hz), 3.47 (dd, 2H, 5.3, 6.2 Hz), 3.40 (s, 6H), 1.30 (t, 3H, 7.1 Hz).
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