[C:1]1([C:7]2[NH:8][C:9](=[O:12])[O:10][CH:11]=2)[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[CH:13](=[CH:20][C:21](=[O:23])[CH3:22])[C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1.CS(O)(=O)=O.O>C(#N)C.C(OCC)(=O)C>[O:23]=[C:21]([CH3:22])[CH2:20][CH:13]([C:11]1[O:10][C:9](=[O:12])[NH:8][C:7]=1[C:1]1[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1)[C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=14-Phenyl-2-oxo-4-oxazoline (1.61 g) and benzalacetone (1.46 g) were dissolved in acetonitrile (20 mL), and methanesulfonic acid (0.96 mL) was added. The obtained mixture was stirred at room temperature for 1 h and water (100 mL) and ethyl acetate (100 mL) were added to the reaction mixture. The organic layer was separated, washed twice with water (50 mL), and concentrated under reduced pressure to give an oily substance. The obtained oily substance was subjected to silica gel column chromatography and eluted with n-hexane-ethyl acetate (1:1). The solvent was evaporated and isopropyl ether (50 mL) was added to the obtained oily substance to allow crystallization and the mixture was stirred at room temperature for 1 h. The crystals were collected by filtration and washed with isopropyl ether (20 mL) to give the title compound (2.65 g; yield 86.3%) as white crystals.
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