As presented in the following reaction formula, a mixture of boran (BH3) in methyl sulfide (Me2S; 1.4 mL, 0.014 mol) was added to a solution of [benzyl-(1-methyl-3-oxo-indan-5-yl)-amino]-acetic acid ethyl ester (4 g, 0.011 mol) and tetrahydrofuran (THF; 50 mL), and the reaction mixture was refluxed for 2 hours. The mixture of BH3 in Me2S (1.4 mL, 0.014 mol) was added several times in a divided manner until there was no reactant left. The reaction was terminated with methanol (10 mL) at 0° C. The resulting mixture was heated to room temperature and stirred for 0.5 hours. The mixture was concentrated to give a crude product. The crude product was purified by silica gel (30 g) column chromatography (product of Merck Co., Ltd.) using an eluent of pentane (PE):ethyl acetate (5:1 (by volume)) to give the desired product [benzyl-(3-hydroxy-1-methyl-indan-5-yl)-amino]-acetic acid ethyl ester (1.4 g, yield: 32%).
