[C:1]([C:4]1[CH:5]=[C:6]([CH:11]=[CH:12][C:13]=1[OH:14])[C:7]([O:9][CH3:10])=[O:8])(=[O:3])[NH2:2].[C:15]([N:22]1[CH2:27][CH2:26][C:25](=O)[CH2:24][CH2:23]1)([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16].N1CCOCC1.C(O)(C(F)(F)F)=O>CO.ClCCl>[C:18]([O:17][C:15]([N:22]1[CH2:27][CH2:26][C:25]2([NH:2][C:1](=[O:3])[C:4]3[CH:5]=[C:6]([C:7]([O:9][CH3:10])=[O:8])[CH:11]=[CH:12][C:13]=3[O:14]2)[CH2:24][CH2:23]1)=[O:16])([CH3:21])([CH3:19])[CH3:20]A mixture of 125 mg (0.64 mmol) of methyl 3-carbamoyl-4-hydroxybenzoate, 192 mg (0.96 mmol) of 1-Boc-4-piperidone, and 120 μL of morpholine in 10 mL of MeOH is refluxed for 72 hr. The MeOH is removed by rotoevapoation, and DCM is added to the residue. Insoluble material is filtered off, and the filtrate is concentrated by rotoevaporation. The residue is purified by preparative TLC to give 93 mg (0.25 mmol, 39% yield) of 1′-(tert-butyloxycarbonyl)-6-methoxycarbonylspiro[1,3-benzoxazine-2,4′-piperidine]-4(3H)-one which on treatment with 40% TFA in dichloromethane gives the TFA salt of 6-methoxycarbonylspiro[1,3-benzoxazine-2,4′-piperidine]-4(3H)-one in quantitative yield.
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