[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][CH2:9][C:10]([NH:15][C:16](=[O:18])[CH3:17])([CH2:13][OH:14])[CH2:11][OH:12])=[CH:4][CH:3]=1.CO[C:21](OC)([CH3:23])[CH3:22].C1(C)C=CC(S(O)(=O)=O)=CC=1>CC(C)=O>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][CH2:9][C:10]2([NH:15][C:16](=[O:18])[CH3:17])[CH2:11][O:12][C:21]([CH3:23])([CH3:22])[O:14][CH2:13]2)=[CH:4][CH:3]=1A solution of N-[3-(4-bromophenyl)-1,1-bis(hydroxymethyl)propyl]acetamide (42.2 g) of Reference Example 4, acetone dimethyl acetal (41.9 g) and a catalytic amount of p-toluenesulfonic acid in acetone (200 mL) was stirred at room temperature for one day. The reaction mixture was concentrated under reduced pressure, and the residual crude crystals were suspended in aqueous sodium hydrogen carbonate solution and collected by filtration to give the title compound (41.5 g) as white crystals.
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