[CH:1]([O:3][CH2:4][CH3:5])=[CH2:2].FC(F)(F)C(O)=O.[OH:13][CH2:14][C@@H:15]1[NH:20][C:19](=[O:21])[CH2:18][CH2:17][CH2:16]1.C([O-])(O)=O.[Na+]>C(Cl)(Cl)Cl>[CH2:1]([O:3][CH:4]([O:13][CH2:14][C@@H:15]1[NH:20][C:19](=[O:21])[CH2:18][CH2:17][CH2:16]1)[CH3:5])[CH3:2]
Ethyl vinyl ether (1.68 mL, 17.5 mmol) and trifluoroacetic acid (0.1 mL) were added sequentially to a solution of (R)-6-hydroxymethylpiperidin-2-one (prepared from D-□-aminoadipic acid according to Huang, et al., Synth. Commun. 1989, 19, 3485-3496, 1.62 g, 12.5 mmol) in CHCl3 (10 mL) at rt. The reaction mixture was stirred at rt for 18 h, then saturated aqueous NaHCO3 (100 mL) was added and the mixture was extracted with CH2Cl2 (3×75 mL). The combined organic phase was dried (Na2SO4), filtered and concentrated in vacuo. Purification of the residue by flash column chromatography on silica gel (CH2Cl2→4% MeOH/CH2Cl2, gradient) afforded 2.03 g (80%) of (R)-6-(1-ethoxyethoxymethyl)-piperidin-2-one.
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