Methanol → (s)-(-)-3-(Benzyloxycarbonyl)-4-oxazolidinecarboxylic methyl ester
Reaction equation
[CH2:1]([O:8][C:9]([N:11]1[C@H:15]([C:16]([OH:18])=[O:17])[CH2:14][O:13][CH2:12]1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.S(Cl)(Cl)=O.[CH3:23]O>>[CH3:23][O:17][C:16]([C@@H:15]1[CH2:14][O:13][CH2:12][N:11]1[C:9]([O:8][CH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1)=[O:10])=[O:18]Participants
4
Procedure
To a stirred solution of (s)-(−)-3-(Benzyloxycarbonyl)-4-oxazolidinecarboxylic acid 9 (1.75 g, 6.96 mmol) in anhydrous methanol (15 mL) was added thionyl chloride (1.02 mL, 13.9 mmol) at 0° C. After 30 minutes, the ice/water bath was removed and the reaction mixture continued to be stirred at room temperature for 3.5 hours. The reaction was quenched by addition of saturated sodium bicarbonate and diluted with dichloromethane (100 mL) and water (50 mL). The mixture was separated and the aqueous layer was extracted with dichloromethane (2×50 mL). The combined organic layers were washed with brine, dried over anhydrous sodium sulfate and filtered. The solvents were removed under reduced pressure and the residue was purified by silica gel chromatography (Hexanes/AcOEt, 1.5:1) to give (s)-(−)-3-(Benzyloxycarbonyl)-4-oxazolidinecarboxylic methyl ester 10 as colorless oil (1.84 g, y=99%). 1H NMR (400 Hz, CDCl3): the compound appears as a pair of distinct rotomers. δ 7.35 (bs, 5H), 5.22-4.99 (m, 4H), 4.53-4.45 (m, 1H), 4.22-4.09 (m, 2H), 3.76 (s, 1.5H), 3.65 (s, 1.5H); MS (m/z). found 288.0 (M+Na)+.