[O:1]=[C:2]1[CH2:7][CH2:6][N:5]([C:8]2[CH:13]=[CH:12][C:11]([NH:14]C(=O)OCC)=[CH:10][CH:9]=2)[CH2:4][CH2:3]1.[CH3:20][O:21][CH2:22][CH:23]1[CH2:27]O[C:25](=[O:28])[O:24]1.C(=O)([O-])[O-].[K+].[K+].C(Cl)Cl>O>[CH3:20][O:21][CH2:22][CH:23]1[O:24][C:25](=[O:28])[N:14]([C:11]2[CH:12]=[CH:13][C:8]([N:5]3[CH2:4][CH2:3][C:2](=[O:1])[CH2:7][CH2:6]3)=[CH:9][CH:10]=2)[CH2:27]1A mixture of 6.0 g of ethyl 4-(4-oxo-piperidin-1-yl)-phenylcarbamate, 5.0 g of 4-methoxymethyl-1,3-dioxolan-2-one and 0.6 g of potassium carbonate was heated to 160° C. under argon for 3 h. The reaction mixture was cooled, treated with methylene chloride and water and the phases were separated. The organic phase was dried with magnesium sulfate and concentrated. The residue (7.8 g) was chromatographed over silica gel 60 using ethyl acetate as the eluent. There was obtained 0.6 g of (RS)-5-methoxymethyl-3-[4-(4-oxo-piperidin-1-yl)-phenyl]-oxazolidin-2-one. 1H-nmr (CDCl3) ppm: 7.46 (d, 2H), 6.98 (d, 2H), 4.76 (m, 1H), 3.99 (t, 1H), 3.88 (t, 1H), 3.64 (d, 2H), 3.57 (t, 4H), 3.44 (s, 3H), 2.56 (t, 4H).
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