4-Nitrophenol → N-Carbobenzoxy-beta-Benzyl-L-Aspartyl-L-Proline p-Nitrophenyl Ester

Participants

Reaction Steps

p-Nitrophenol (3.0 Kg) is added to the concentrated ethyl acetate solution of N-carbobenzoxy-β-benzyl-L-aspartyl-L-proline prepared as described in Example II above. The solution is cooled below 5° C. Dicyclohexylcarbodiimide (4.5 Kg) is dissolved in ethyl acetate (10-20 L) and added, maintaining the temperature below 5° C. The solution is stirred at reduced temperature for two hours and then for three hours at 20°-30° C. The dicyclohexylurea is removed by filtration and washed with ethyl acetate (20-30 L). The filtrate is concentrated in vacuo below 60° C. The concentrate is dissolved in hot isopropyl alcohol (50-70 L) and cooled below 25° C. The solids are collected on a filter, rinsed with isopropyl alcohol and dried below 40° C. Melting point=88°-91° C.; specific rotation=-70° to -73° (C=1, ethyl acetate).

Provenance & Evidence