Compound 8b

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Compound data: CIF

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

To a solution of 6a (60.8 mg, 0.3557 mmol) and methyl 2,3-dihydroxybenzoate 7 (125.5 mg, 0.747 mmol) in CH₂Cl₂ (3 mL) is added diacetate iodobenzene (229.0 mg, 0.711 mmol) at RT. The reaction mixture was stirred 15 hr and was then quenched with a saturated aqueous NaHCO₃ solution. The aqueous phase was extracted twice with ethyl acetate. The combined organic phases were dried with Na₂SO₄, filtered and concentrated to dryness. The residue was then purified by flash chromatography over silica gel (elution gradient: pentane/ethyl acetate 90:10 80:20) affording 8a (27.0 mg, 22%) and 56 mg of a 2:1 mixture of 7 and 8b (which represents for 8b: 28 mg, 23%). 8b; IUPAC name: (5aR*,10bR*)-methyl 11H-4b,10a-butanobenzo[5,6][1,4]dioxino[2,3-b]indole-9-carboxylate. White solid, melting point: 130 °C (decomp.) R_f = 0.50 (pentane/AcOEt 80:20). IR (neat): ν _max = 3346, 2946, 1720, 1617, 1466, 1274, 1195, 1144, 1021, 935, 901, 863, 752 cm^–1. HRMS ESI: m/z [MH]⁺: 360.1196 ; calculated for C₂₀H₁₉NNaO₄⁺: 360.1206. ¹H NMR (360 MHz, chloroform-d), δ (ppm): 7.28 (dd, J = 7.5; 1.8 Hz, 1H), 7.21 (d, J = 7.5 Hz, 1H), 7.08 (t, J = 7.5 Hz, 1H), 6.82-6.69 (m, 4H), 4.36 (br s, 1H), 3.91 (s, 3H), 2.35 (d, J = 12.9 Hz, 1H), 2.10 (d, J = 12.9 Hz, 1H), 1.80-1.55 (m, 6H). ¹³C NMR (90 MHz, chloroform-d), δ (ppm): 166.5, 146.5, 144.2, 142.3, 132.6, 129.3, 123.2, 122.8, 120.7, 120.5, 120.2, 111.6, 94.5, 82.0, 52.1, 37.5, 31.3, 23.3, 20.4.