C(N=C=NCCCN(C)C)C.[CH2:12]([C@@H:19]1[CH2:23][O:22][C:21](=[O:24])[NH:20]1)[C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1.[O:25]1[CH2:29][CH2:28][CH:27]([C:30](O)=[O:31])[CH2:26]1.O>CN(C1C=CN=CC=1)C.C(Cl)Cl>[CH2:12]([C@@H:19]1[CH2:23][O:22][C:21](=[O:24])[N:20]1[C:30]([C@H:27]1[CH2:28][CH2:29][O:25][CH2:26]1)=[O:31])[C:13]1[CH:14]=[CH:15][CH:16]=[CH:17][CH:18]=11-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI; 362 mg, 1.90 mmol) and DMAP (202 mg, 1.90 mmol) were added to a solution of (R)-4-benzyl-oxazolidin-2-one (333 mg, 1.90 mmol) and tetrahydrofuran-3-carboxylic acid (200 mg, 1.70 mmol) in CH2Cl2 (20 mL) at ambient temperature. The reaction mixture was stirred for 3 h at ambient temperature and water (20 mL) was added. The two layers were separated and the aqueous phase was extracted with CH2Cl2 (20 mL×3). The combined organic phases were washed with brine (50 mL×3), dried over anhydrous sodium sulfate and concentrated. The residue was purified by flash column chromatography on silica gel (CH2Cl2/EtOAc=100:2) to afford (R)-4-benzyl-3-((S)-tetrahydrofuran-3-carbonyl)oxazolidin-2-one (120 mg, 25% yield).
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