Reaction Steps
To a solution of N′-hydroxy-3-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]benzenecarboximidamide (0.36 g, 0.84 mmol) in pyridine (3 mL) was added acetyl chloride (0.12 mL, 1.68 mmol). The reaction was stirred in a microwave reactor (170° C., 200 watts, 200 psi) for 30 min. The mixture was concentrated in vacuo. The residue was purified by column chromatography with ethyl acetate in hexanes (25% to 40% gradient), and recrystallized from ethyl acetate and diethylether to afford 1′-[3-(5-methyl-1,2,4-oxadiazol-3-yl)benzyl]-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one (0.27 g, 71%) as a colorless solid: mp 209-213° C.; 1H NMR (300 MHz, CDCl3) δ8.06-8.03 (m, 1H), 7.99-7.96 (m, 1H), 7.48-7.44 (m, 2H), 7.19-7.12 (m, 2H), 7.03-6.98 (m, 1H), 6.77-6.74 (m, 1H), 6.58 (s, 1H), 6.42 (s, 1H), 5.18 (d, J=15.8 Hz, 1H), 5.00 (d, J=9.0 Hz, 1H), 4.85 (d, J=15.8 Hz, 1H), 4.72 (d, J=9.0 Hz, 1H), 4.56-4.50 (m, 2H), 3.07-2.95 (m, 2H), 2.63 (s, 3H); 13C NMR (75 MHz, CDCl3) δ178.0, 176.7, 168.1, 161.9, 161.3, 141.9, 136.6, 132.8, 129.9, 129.6, 128.8, 127.5, 126.9, 126.0, 124.0, 123.6, 120.2, 120.1, 119.1, 109.2, 93.2, 80.6, 72.4, 57.8, 43.8, 29.1, 12.4; MS (ES+) m/z 451.8 (M+1).
