To a suspension of [[926|methyl (2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoate]] (5.02 g, 16.2 mmol) in tetrahydrofuran (50 mL) was added a solution of lithium hydroxide (4 eq, 1.55 g) in water (50 mL). The reaction mixture turned clear after about 10 minutes, then a precipitate began to develop again which had become thick after 90 minutes. The reaction mixture was stirred another 90 minutes. TLC indicated the absence of starting material. The reaction mixture was poured into 1M hydrochloric acid (200 mL) and stirred vigorously for 1 hour. The precipitate was then filtered off and washed with plenty of water in the filter. Suction drying then drying by azeotropic distillation with acetonitrile afforded the title compound as a white solid (4.58 g, 95 %).

d_H (400 MHz, DMSO-d₆) 12.64 (1H, br s, COOH), 8.73 (1H, d, J 7.44, NH), 8.14 (2H, d, J 7.60, H_Ar), 8.24 (2H, d, J 8.24, H_Ar), 7.42 (2H, ddd, J 8.20, 7.12, 1.12, H_Ar), 7.22-7.18 (2H, m, H_Ar), 5.12 (1H, d, J 17.21, NCH_aH_b), 5.02 (1H, d, J 16.81, NCH_aH_b), 4.25 (1H, pseudo-quintet, J 7.30, CH^*), 1.33 (3H, d, J 7.28, CH₃). d_C (100 MHz, DMSO-d₆) 173.89 and 167.29 (C=O), 140.64, 125.62, 122.22, 120.10, 118.96, and 109.40 (C_Ar), 47.67 (CH^*), 45.28 (NCH₂), 17.36 (CH₃). HRMS (ESI) m/z: [M+Na]⁺ calcd for C₁₇H₁₆N₂NaO₃ 319.1053; found 319.1047.