Triethylamine → 4(S)-(Methoxycarbonyl)-N-benzyl-1,3-oxazolidine-2-thione

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Reaction Steps

Thiophosgene (23.8 g, 207 mmol) in dry THF (200 mL) was slowly added to a solution of N-benzyl-L-serine (43.4 g, 207 mmol), triethylamine (41.9 g, 414 mmol) in dry THF (600 mL) at 60° C. under nitrogen. The mixture was stirred for 3 hours, and was stirred at room temperature for 12 hours. Triethylamine hydrochloride was removed by filtration and the solvent was evaporated in vacuo. The residue was purified by silica gel column chromatography eluted with ethyl acetate/n-hexane (1/1=v/v). Recrystallization from a mixed solvent [THF/n-hexane (2/1=v/v)] gave BnSL (40.1 g, 77%) as a white powder. [α]D25=35.0° (c=0.1 g/dL, in CH2Cl2). m.p.=101.3–101.8° C. 1H NMR (CD2Cl2): δ=3.70 (s, 3H, —OCH3), 4.32–4.37 (m, 1H, —CH2—), 4.54–4.59 (3H, —CH<, —CH2—, and —CH2—C6H5), 5.31–5.42 (m, 1H, —CH2—C6H5), 7.33–7.38 (5H, —C6H5) ppm. 13C NMR (CD2Cl2): δ=51.47 (—CH2—C6H5), 53.06 (—OCH3), 59.90 (—CH<), 65.55 (—CH2—), 128.98, 129.04, 129.48, 135.09 (—C6H5), 169.55 (—COOCH3), 189.39 (—OCSNH—) ppm. IR (KBr): 1743 (—COOCH3), 1481 (C═S), 1450, 1357, 1304, 1211, 971, 701 cm−1. C12H13NO3S: Calcd. C 57.35, H 5.21, N 5.57, S 12.76; Found C 57.54; H 5.19; N 5.64, S 12.72.

Provenance & Evidence