A solution of compound 31 (2.03 g, 7.4 mmol) in DMF (50 mL) was treated with sodium bicarbonate (1.8 g, 21.4 mmol), and benzyl bromide (4 mL, 33.6 mmol). The reaction mixture was stirred for 18 h at room temperature. Water (50 mL) was added and the product was extracted with ethyl acetate (80 mL×3). The solution was dried with sodium sulfate, concentrated in vacuo to give compound 32 (2.27 g, 84% yield) as a white solid. m.p.180°-182° C. 1H NMR (DMSO-d6, ppm): 11.93 (s, 1 H, NH), 7.51-7.02 (m, 9 H, Ar--H), 5.38 (s, 2 H, CH2C6 H5), 1,48 (s, 9 H, C(CH3)3). Anal. (C21H22 N2O4 0.25H2O), C, H, N.
