Under nitrogen atmosphere, 9-bromo-3-chloro-8-hydroxy-6,6-dimethyl-5,6-dihydro-benzo[b]carbazol-11-one (Compound S2-4, 76 mg, 0.2 mmol) and triphenylphosphine (69 mg, 1.3 eq.) were added with THF (2 ml), and ((S)-2,2-dimethyl-[1,3]dioxolan-4-yl)-methanol (35 mg, 1.3 eq.) and 2.19 N toluene solution (118 μL, 1.3 eq.) of diethyl azodicarboxylic acid were added dropwise thereto, followed by stirring at 50° C. for 2 hr. After cooling, the reaction solution was added with ethyl acetate, washed with brine, dried over sodium sulfate and filtered. The residues obtained after concentration under reduced pressure were purified by silica gel column chromatography (ethyl acetate/dichloromethane) to give a solid, which was then washed with dichloromethane to obtain the title compound (brown powder, 53 mg).
