To a stirred solution of benzoic acid 3-(benzenesulfonyl-benzyl-amino)-4-benzyloxy-phenyl ester (which was obtained in Example 18) (1.80 g, 3.28 mmol) in THF (10 mL) and methanol (10 mL) was added 10% of sodium hydroxide (10 mL). The mixture was stirred at room temperature for 1.5 hours, acidified with concentrated hydrochloric acid and diluted with water (200 mL). The aqueous solution was extracted with CH2Cl2. The organic phase was dried over MgSO4 and concentrated. The product was purified by flash silica gel chromatography eluting with ethyl acetate and hexanes to give the title compound as a white solid (1.20 g, 82%); 1H NMR (300 MHz, CDCl3) δ 4.71 (brs, 4H), 6.49 (d, J=3.0 Hz, 1H), 6.62(dd, J=9.0, 3.0 Hz, 1H), 6.84 (d, J=9.0 Hz, 1H), 7.10-7.70 (m, 15H), 9.07 (brs, 1H); MS (ES) m/z: 444.0 ((M−H)−, 100%); HRMS Calcd. for C26H22NO4S(M−H)−: 444.1275. Found: 444.1270.
