Reaktionsschritte
To a mixture of spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (0.96 g, 3.41 mmol) in 2-butanone (17 mL) and acetone (17 mL) were added cesium carbonate (3.79 g, 11.6 mmol) and N-Boc-3-(2-bromoethyl)piperidine (1.00 g, 3.42 mmol) at ambient temperature. The mixture was stirred at ambient temperature for 16 h. The reaction mixture was filtered and washed with acetone (2×50 mL). The filtrate was concentrated in vacuo to dryness. The residue was purified by column chromatography with ethyl acetate in hexanes (10% to 30% gradient) to give tert-butyl 3-[2-(2′-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-1′(2′H)-yl)ethyl]piperidine-1-carboxylate (1.48 g, 88%) as a white powder: mp 64-67° C. (diethyl ether/hexanes); 1H NMR (300 MHz, CDCl3) δ 7.30 (dt, J=7.8, 0.9 Hz, 1H), 7.16 (d, J=7.3 Hz, 1H), 7.50 (dt, J=7.5, 0.7 Hz, 1H), 6.92 (d, J=7.8 Hz, 1H), 6.50 (s, 1H), 6.10 (d, J=1.7 Hz, 1H), 5.86 (dd, J=6.0, 1.0 Hz, 2H), 4.90 (dd, J=9.0, 0.6 Hz, 1H), 4.65 (dd, J=9.0, 3.0 Hz, 1H), 3.90-3.69 (m, 4H), 2.97-2.86 (m, 1H), 2.77-2.68 (m, 1H), 1.96-1.92 (m, 1H), 1.76-1.16 (m, 15H); 13C NMR (75 MHz, CDCl3) δ 177.2, 155.8, 154.8, 148.8, 142.3, 142.2, 142.1, 132.4 (2), 128.9, 124.0, 123.2, 119.4 (2), 108.5, 102.9, 101.4, 93.6, 80.4, 79.4, 58.1, 38.2, 33.5, 30.7, 30.7, 30.6, 30.5, 28.4, 24.3; MS (ES+) m/z 515.4 (M+23).
