Trifluoroacetic acid → 3-[4-(2-{4-[(2,3-Dihydro-indole-1-carbonyl)-amino]-3-methoxy-phenyl}-acetylamino)-phenyl]-butyric acid

A solution of tert-butyl 3-[4-(2-{4-[(2,3-dihydro-indole-1-carbonyl)-amino]-3-methoxy-phenyl}-acetylamino)-phenyl]-butyrate [580 mg, Reference Example 1(a)] in dichloromethane (20 ml) was treated with treated with trifluoroacetic acid (1 ml). After 2 hours at room temperature further (1 ml) trifluoroacetic acid was added and the solution was then kept at room temperature overnight. The reaction mixture was evaporated and the residue was suspended in water. This suspension was treated with 1.0 M sodium hydroxide solution (5 ml) and then washed twice with ethyl acetate, then acidified to pH 1 with hydrochloric acid and then filtered. The resultant white solid was washed with water then dried to give the title compound (450 mg) as a white powder, m.p. 152-154° C. [Elemental analysis: C, 67.35; H, 6.02; N, 8.46%. Calculated for C28H29N3O5.0.63H2O: C, 67.41; H, 6.11; N, 8.42%].