t-Butoxycarbonyl -β-alanine (16.1 g, 0.080 mole) in dimethylformamide (200 ml) was cooled to 0°, and triethylamine (23.8 ml, 0.17 mole) was rapidly added. The solution was kept at -5° to 0° while isobutylchloroformate (11.9 ml, 0.085 mole) was added dropwise. The solution was stirred 10 minutes and then 1-{[5-(4-cyanophenyl)furfurylidene]amino}hydantoin (recrystallized and predried at 100° overnight; 23.5 g, 0.080 mole) was rapidly added. The mixture was maintained at -5° to 0° for 0.5 hr and was then stirred 1 hour without cooling. The mixture was poured into a solution of ice water (1,400 ml) and concentrated hydrochloric acid (25 ml). The resulting solid was collected and air-dried. The product was dissolved in acetonitrile, filtered, and concentrated to a solid.
