L-Serine (2.10 g, 20.0 mmol) (Wako Pure Chemical Industries, Ltd.) was dissolved in methylene chloride (20 mL) (Wako Pure Chemical Industries, Ltd.), and then trimethylsilyl chloride (8.9 mL) (Shin-Etsu Chemical Co., Ltd.) was added thereto, followed by reflux for 20 minutes. The mixture was returned to room temperature, and then triethylamine (10 mL) (Wako Pure Chemical Industries, Ltd.) was added thereto, followed by reflux for 45 minutes. The mixture was ice-cooled, and then triethylamine (2.8 mL) (Wako Pure Chemical Industries, Ltd.) and triphenylchloromethane (5.61 g, 20.1 mmol) (Wako Pure Chemical Industries, Ltd.) were added thereto, followed by stirring at room temperature for 5 hours. An excessive amount of methanol (Wako Pure Chemical Industries, Ltd.) was added to the reaction solution, and the mixture was concentrated under reduced pressure. The organic layer was dried with anhydrous sodium sulfate (Wako Pure Chemical Industries, Ltd.), and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography (chloroform (Wako Pure Chemical Industries, Ltd.):methanol (Wako Pure Chemical Industries, Ltd.)=99:1 as an eluent), to thereby obtain the title compound (0.36 g, 5% yield).
