General procedure for the synthesis of D-serine methyl ester hydrochloride from methanol and D-serine:
4.2.1.1 Synthesis of methyl (R)-2-isopropyl-4,5-dihydrooxazole-4-carboxylate
First, sulfoxide chloride (SOCl, 7.60 mL, 104.2 mmol) was slowly added dropwise to a methanolic solution of D-serine (10.0 g, 95.1 mmol) and the reaction mixture was stirred for 24 h at room temperature. After completion of the reaction, the solvent was removed by rotary evaporator to give a white solid. The solid was washed with hexane (3 x 25 mL) to give D-serine methyl ester hydrochloride (14.4 g, 97% yield) as a colorless solid. The product was characterized by 1H NMR (300 MHz, DO) with the following chemical shifts: δ 4.32-4.28 (1H, m, CH), 4.12 (1H, dd, J = 4.2, 12.5 Hz, CHaHbOH), 4.02 (1H, dd, J = 3.4, 12.5 Hz, CHaHbOH), 3.88 (3H, s, CH) .
