[O:1]=[C:2]1[C:6]2([CH2:11][CH2:10][N:9]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:8][CH2:7]2)[CH2:5][CH2:4][CH2:3]1.[CH:19](OCC)=[O:20].CC(C)([O-])C.[K+].Cl>C(OCC)C>[OH:20][CH2:19][CH:3]1[CH2:4][CH2:5][C:6]2([CH2:7][CH2:8][N:9]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:10][CH2:11]2)[C:2]1=[O:1]tert-Butyl 1-oxo-8-azaspiro[4.5]decane-8-carboxylate from Procedure 1, Step G (0.526 g, 2.08 mmol) was dried by evaporating with toluene (10 mL) three times in vacuo, dissolved in methyl-tert-butyl ether (5 mL), and cooled to −78° C. To this solution was added ethyl formate (0.336 mL, 4.15 mmol) and then potassium t-butoxide (0.466 g, 4.16 mmol). After 2 days, the reaction mixture was diluted with diethyl ether, poured into 2N HCl, and extracted three times with diethyl ether. The organic layers were combined, washed with brine, dried over sodium sulfate, filtered, and concentrated to afford 0.575 g. The residue was purified by flash chromatography eluting with 45% ethyl acetate/hexanes to give the title compound (0.303 g). MS/EI (acetonitrile/water): m/z 304 (M+1+Na) retention time=2.9 min.
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