[N:1]([O-])=O.[Na+].C(O)(=O)C.[CH3:9][O:10][CH:11]([O:30][CH3:31])[CH:12]([NH:14][C:15]1[CH:20]=[C:19]([O:21][CH2:22][C:23]2[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=2)[CH:18]=[CH:17][C:16]=1[NH2:29])[CH3:13]>O.C(COC)OC>[CH3:9][O:10][CH:11]([O:30][CH3:31])[CH:12]([CH3:13])[N:14]1[C:15]2[CH:20]=[C:19]([O:21][CH2:22][C:23]3[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=3)[CH:18]=[CH:17][C:16]=2[N:29]=[N:1]1A solution of NaNO2 (34 g, 0.492 mole) in water is added to a cold (3° C.) solution of acetic acid and water. A cold (4° C.) solution of 2-[2-amino-5-(benzyloxy)anilino]-propionaldehyde dimethyl acetal in dimethoxyethane is then added in one portion to the vigorously-stirred NaNO2 acetic acid solution. The reaction temperature rises to 22° C. The reaction mixture is stirred at 18°-22° C. for 20 minutes, cooled to 5° C., and filtered. The solid filter cake is washed with water and dried at 50° C., to give the title product as a white solid, 75.7 g (65.7%). A sample is recrystallized twice from 1:1 toluene-heptane solution to a white solid, mp 101°-103° C. (sinter 100° C.), identified by elemental and NMR analyses.
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