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Compound 57:; Chiral To a 5.5 N HCI solution (7.2 mL) of 1 ,2-diamino-3,5-difluorobenzene (1.04 g, 7.19 mmol) was added D-aspartic acid (1.44 g, 10.8 mmol). The mixture was refluxed for overnight. The reaction crude was purified by prep. HPLC to give the title compound as an acetic acid salt in 57% yield. 1H NMR (DMSO- d6): delta 7.22 (1 H, dd, J=8.6, 2Hz), 7.02 (1 H, td, J=10.6, 2Hz), 4.21 (1 H, t, J=6.3Hz), 3.44 (1 H, dd, J=16.2, 5.6Hz), 3.29 (1 H, dd, J=16.4, 7Hz). LCMS (API-ES): 242.1 (M+H+).
[00222] Acetyl chloride (54.6 mL, 0.75 mol) was added drop- wise into ethanol (316 mL) at 0-5 0C. When the addition was completed, the ice bath was removed and the solution allowed to stir while warming to room temperature for another 30 min. D-aspartic acid 19.1 (25 g, 0.188 <n="77"/>mol) was then added. The reaction mixture was refluxed for 2 hours. The reaction solution was then concentrated in vacuo and placed under high vacuum (0.4 mm Hg) overnight. Compound 19.2 was obtained as a white solid (42 g, 99%) and used directly in the next step.