Palladium on carbon (10%, 40 mg) was added to 25d (200 mg, 0.36 mmol) in anhydrous THF (2.40 mL) and the solution was placed under an atmosphere of H2. After 12 hours, the solution was filtered through SiO2 (1:1 CH2Cl2:Acetone) and the eluent was concentrated to afford a yellow solid, which was used without further purification (150 mg, 99%). EDCI (57.5 mg, 0.30 mmol) and 1H-indole-2-carboxylic acid (38.7 mg, 0.24 mmol) were added to the amine (50.6 mg, 0.12 mmol) in 30% pyridine/CH2Cl2 (3.30 mL). After 12 hours, the solvent was concentrated and the residue purified via column chromatography (SiO2, 40:1 CH2Cl2:Acetone) to afford a colorless solid, which was used without further purification (26.3 mg, 39%). Triethylamine (150 μL) was added to the carbonate (26.3 mg, 0.047 mmol) in MeOH (2.00 mL) and CH2Cl2 (2.00 mL). After 48 hours, the solvent was concentrated and the residue purified via column chromatography (SiO2, 40:1 CH2Cl2:Acetone) to afford 26l as a colorless amorphous solid (6.60 mg, 26%, 10% over 3 steps): 1H NMR (CD2Cl2, 400 MHz) δ 9.26 (s, 1H), 8.96 (s, 1H), 8.68 (s, 1H), 7.74 (d, J=8.1 Hz, 1H), 7.52 (d, J=8.3 Hz, 1H), 7.38-7.34 (m, 1H), 7.22-7.16 (m, 1H), 6.84 (s, 1H), 6.00 (s, 1H), 5.65 (d, J=1.7 Hz, 1H), 4.26-4.21 (m, 2H), 3.96 (s, 3H), 3.59 (s, 3H), 3.35 (d, J=8.6 Hz, 1H), 2.25 (s, 3H), 1.53 (s, 3H), 1.20 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 165.1, 157.4, 156.5, 149.7, 136.7, 134.7, 127.7, 125.3, 122.5, 121.1, 120.0, 111.9, 104.6, 103.8, 97.7, 94.0, 84.3, 84.2, 82.6, 69.6, 69.1, 66.1, 62.2, 62.0, 59.7, 23.1, 22.7, 14.2; IR (film) νmax 3389, 2924, 2853, 1697, 1605, 1535, 1460, 1340, 1211, 1101, 1088, 962, 729 cm−1; HRMS (ESI+) m/z: [M+H]+ calcd for C28H30N2O9, 539.2030. found, 539.2056.
