[C:1]([O:5][C:6]([NH:8][C:9]1[CH:10]=[C:11]([CH:15]=[C:16]([NH:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH:17]=1)[C:12](O)=[O:13])=[O:7])([CH3:4])([CH3:3])[CH3:2].O>C1COCC1>[C:1]([O:5][C:6]([NH:8][C:9]1[CH:10]=[C:11]([CH2:12][OH:13])[CH:15]=[C:16]([NH:18][C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH:17]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2]A 2.00 g (5.68 mmol) portion of 3,5-di-(tert-butoxycarbonylamino)benzoic acid was dissolved in 15 ml of THF, 3.77 ml (39.7 mmol) of borane-methyl sulfide complex dissolved in 10 ml of THF was added dropwise to the thus prepared solution, and the mixture was stirred at room temperature for 5 hours. The reaction solution was cooled to 0° C., mixed with water and extracted with ethyl acetate. The ethyl acetate layer was washed with saturated brine and dried with anhydrous sodium sulfate, and then the solvent was evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography (chloroform/methanol=20/1) to obtain 1.08 g (yield, 56%) of 1,3-di-tert-butoxycarbonylamino-5-hydroxymethylbenzene.
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