Reaction Steps
A solution of (E)-3-sec-butyl-2-hydroxy-5-(3-oxo-3-(3,4,5-trimethoxyphenyl)prop-1-enyl)benzaldehyde of formula III (0.5 g, 1.26 mmol), diethyl malonate (0.20 g, 1.26 mmol) in ethanol (30 mL) was treated with piperidine (0.2 mL) and refluxed. Most of the excess solvent was evaporated under reduced pressure, and the residue was neutralized with acetic acid. To this residue water (35 mL) was added and extracted 3-fold with 15 mL of CHCl3. The combined organic layers were dried on Na2SO4, filtered, and concentrated to dryness under reduced pressure. The residue was chromatographed over silica gel (SiO2, 230-400 flash), eluting with a gradient of 20% ethyl acetate in hexane to 40% ethyl acetate in hexane, which upon concentration provides (E)-ethyl 8-sec-butyl-2-oxo-6-(3-oxo-3-(3,4,5-trimethoxyphenyl)prop-1-enyl)-2 H-chromene-3-carboxylate (General Formula IV). (0.49 g, 78% yield). White solid, m. p. 128-129° C.; 1H NMR (CDCl3 300 MHz): δ 8.56 (s, 1H), 7.83-7.75 (m, 3H), 7.49 (d, J=15.6 Hz, 1H), 7.31-7.29 (m, 2H), 4.42 (q, J=7.1 Hz, 2H), 3.95 (brs, 9H), 3.45-3.36 (m, 1H), 1.78-1.69 (m, 2H), 1.42 (t, J=7.1 Hz, 3H) 3.33 (d, J=6.9 Hz, 3H) 0.89 (t, J=7.3 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 188.8, 162.9, 156.3, 153.9, 153.3, 148.6, 142.9, 142.7, 136.7, 133.2, 131.8, 131.6, 126.8, 122.7, 118.8, 118.2, 106.4, 62.1, 61.1, 56.6, 50.8, 33.6, 29.7, 20.5, 14.3, 12.1; ESI-MS (m/z): 495 (M+H)+.
