5-benzyl-N-(3-chloro-4-fluorophenyl)-3-(2,4-difluorobenzyl)-4-oxotetrahydropyrimidine-1(2H)-carboxamide (51)

According to the procedure for preparation of compound 21, 2-benzyl-3-((tert-butoxycarbonyl)amino)propanoic acid (60 mg, 0.215 mmol) was treated with 2,4-difluorobenzylamine (31 mg, 0.215 mmol), EDC·HCl (41 mg, 0.215 mmol), HOBt·H₂O (33 mg, 0.215 mmol), and excess triethylamine, and then continued the same procedure to afford 51. ¹H NMR (300 MHz, CDCl₃): δ (ppm) 7.41–7.36 (m, 1H), 7.36–7.23 (m, 4H), 7.23–7.17 (m, 2H), 7.15–7.07 (m, 1H), 7.04–6.96 (m, 1H), 6.88–6.74 (m, 2H), 5.03–4.95 (m, 1H), 4.76–4.70 (m, 1H), 4.70–4.55 (m, 2H), 3.64–3.55 (m, 1H), 3.45–3.36 (m, 1H), 3.00–2.85 (m, 1H), 2.74–2.62 (m, 1H); Calculated for C₂₅H₂₁ClF₃N₃O₂, 487.1; observed (M + H)⁺ 488.6.