... European Journal of Medicinal Chemistry. ... Medicinal Chemistry Research Center ... residue was purified by silica gel column chromatography (n-hexane/ethyl acetate = 1:3) to give 4 (109.1 g, 93%) as a pale yellow powder: mp 110–112 °C; 1 H NMR (CDCl 3 ) δ 8.21 (d, J = 8.7 Hz ...