Compound 1a

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InChIKey NUDGCFHYMWIOOP-UHFFFAOYSA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

To a red suspension of benzyl protected intermediate (2.0 mmol) in MeOH (10 mL) was added 10% palladium on carbon catalyst (0.2 mmol). The insoluble mixture was stirred with a hydrogen balloon at room temperature for about 1 hour. After the red color disappeared, the mixture was diluted with DCM (20 mL), filtrated with celite and evaporated to give a residue, which was purified by column chromatography on silica gel to yield 1a as a white solid. ¹H-NMR (500MHz, CDCl₃): δ 8.01-7.99 (m, 2H), 7.59-7.57 (m, 1H), 7.49-7.46 (m, 2H), 7.37-7.24 (m, 7H), 7.14 (t, J = 7.5 Hz, 1H), 6.74 (d, J = 8.0 Hz, 1H), 4.98 (s, 2H), 4.18 (dd, J = 9.0, 3.0 Hz, 1H), 3.90 (dd, J = 18.0, 3.0 Hz, 1H), 3.41 (dd, J = 18.5, 9.0 Hz, 1H). ¹³C-NMR (125 MHz, CDCl₃): δ 196.80, 177.77, 143.40, 136.32, 135.88, 133.45, 129.04, 128.76, 128.71, 128.68, 128.15, 127.96, 127.57, 124.38, 122.50, 109.03, 43.94, 41.20, 40.05. HRMS (ESI) calcd for [M+H] C₂₃H₂₀NO_2, m/z: 342.1488, observed: 342.1491.