Reaction Steps
A suspension of (S)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one (1.0 g, 3.4 mmol), cesium carbonate (3.3 g, 10.2 mmol) and 1-bromopentane (1.02 g, 6.77 mmol) in anhydrous 1,4-dioxane (25 mL) was heated at reflux under nitrogen for 2 h. The reaction mixture was allowed to cool to ambient temperature, filtered and concentrated in vacuo. Purification of the residue by column chromatography and eluted with a 15% to 50% gradient of ethyl acetate in hexanes, followed by recrystallization from methanol afforded (S)-t-pentyl-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one as an off-white solid (0.89 g, 72%): mp 111-113° C. (ethyl acetate/hexanes); 1H NMR (300 MHz, CDCl3) δ 7.23-7.30 (m, 1H), 7.13 (dd, J=7.4, 0.9 Hz, 1H), 7.00-7.03 (m, 1H), 6.89 (d, J=7.8 Hz, 1H), 6.46 (s, 1H), 6.19 (s, 1H), 4.73 (ABq, 2H), 4.19-4.05 (m, 4H), 3.86-3.59 (m, 2H), 1.82-1.62 (m, 2H), 1.43-1.28 (m, 4H), 0.89 (t, J=6.9 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ177.2, 155.2, 144.5, 142.4, 138.2, 132.5, 128.7, 123.9, 123.0, 121.1, 111.4, 108.5, 99.3, 80.1, 64.5, 63.9, 58.0, 40.3, 29.0, 27.1, 22.3, 14.0; MS (ES+) m/z 366.0 (M+1).
