N12CCCN=C1CCCC[CH2:2]2.[NH:12]([CH2:19][C:20]1([OH:36])[CH2:25][CH2:24][CH2:23][N:22]([C:26]([O:28][CH2:29][C:30]2[CH:35]=[CH:34][CH:33]=[CH:32][CH:31]=2)=[O:27])[CH2:21]1)[C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1.[OH2:37]>C(#N)C>[O:37]=[C:2]1[N:12]([C:13]2[CH:14]=[CH:15][CH:16]=[CH:17][CH:18]=2)[CH2:19][C:20]2([CH2:25][CH2:24][CH2:23][N:22]([C:26]([O:28][CH2:29][C:30]3[CH:35]=[CH:34][CH:33]=[CH:32][CH:31]=3)=[O:27])[CH2:21]2)[O:36]1N,N′-Carbonyldiimidazole (1.5 g) and 1,8-diazabicyclo[5.4.0]undec-7-ene (2.5 g) were added to benzyl 3-(anilinomethyl)-3-hydroxypiperidine-1-carboxylate (2.2 g) obtained by the above-mentioned reaction in acetonitrile (35 mL), and the mixture was stirred at 80° C. for 20 hr. The reaction solution was poured into water, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over sodium sulfate and concentrated. The residue was purified by silica gel column chromatography (25% ethyl acetate/hexane to 50% ethyl acetate/hexane) to give crude benzyl 2-oxo-3-phenyl-1-oxa-3,7-diazaspiro[4.5]decane-7-carboxylate (2.0 g).
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