4-Chloro-3-hydroxybutyric acid ethyl ester, (3R)- → [(R)-3-(2,3-dihydro-benzo[1,4]dioxin-6-yl)-2-oxo-oxazolidin-5-yl]-acetic acid ethyl ester

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A solution of ethyl (R)-4-chloro-3-hydroxybutyrate (5.0 g, 30 mmol) and 2,3-dihydro-1,4-benzodioxin-6-yl isocyanate (5.3 g, 30 mmol) in benzene (150 ml) was stirred at 80° C. for 48 h. The reaction mixture was concentrated in vacuo, taken up in EA and washed twice with brine. The org. layer was dried over MgSO4 and concentrated. The residue was purified by chromatography on SiO2 (hept/EA 9:1 to 1:1) to give the desired carbamate (8.3 g, 81% yield) as a yellow oil. This intermediate was dissolved in DMF (40 ml) and treated with K2CO3 (3.3 g, 24 mmol). The heterogeneous mixture was stirred at rt for 20 h, water was added and the mixture extracted with EA. The org. layers were washed with water and brine, dried over MgSO4 and concentrated. The residue was purified by chromatography on SiO2 (Hept/EA 2:1, 1:1) to give the desired oxazolidinone (0.96 g, 13% yield) as an orange solid.

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