Hydrochloric Acid → 2-(S)-(benzooxazol-2-ylamino)-3-cyclohexyl propionic acid

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Reaction Steps

A slurry of L-cyclohexylalanine (2.44 g, 14.3 mmol) and powdered NaOH (1.14 g, 28.6 mmol) in DMSO (20 mL) was heated to 100° C. for 20 min until the mixture viscosity decreased and stirring was enabled. 2-Chlorobenzoxazole (1.99 g, 13.0 mmol) was added, and the solution was stirred at 100° C. for 4 h. Upon cooling to room temperature, the solution was poured into 1 M HCl. The precipitate was filtered and dried to afford 2-(S)-(benzooxazol-2-ylamino)-3-cyclohexyl propionic acid was isolated as a white powder (1.69 g, 41%). Step B. To a stirring solution of 2-(S)-(benzooxazol-2-ylamino)-3-cyclohexyl propionic acid (288 mg, 1.0 mmol), N1-(4-methoxy-phenyl)-ethane-1,2-diamine.2HCl (239 mg, 1.0 mmol), and iPr2NEt (0.87 mL, 5.0 mmol) in dichloromethane (4 mL) was added HATU (418 mg, 1.1 mmol). The solution was stirred at room temperature for 4 hours and then evaporated to dryness. The crude material was chromatographed over silica gel (Hexanes/EtOAc) to afford the title compound as a white powder (243 mg, 56%). HPLC-MS calcd. for C25H32N4O3 (M+H+) 437.25. found 437.5.

Provenance & Evidence