[OH:1][C@H:2]1[CH2:6][O:5][CH2:4][C@@H:3]1[O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[N:11]=[C:10]([N:18]2[CH2:23][CH2:22][NH:21][CH2:20][CH2:19]2)[N:9]=1.CC(C)=[O:26]>>[C:6]([OH:26])(=[O:5])[CH3:2].[OH:1][C@H:2]1[CH2:6][O:5][CH2:4][C@@H:3]1[O:7][C:8]1[C:17]2[C:12](=[CH:13][CH:14]=[CH:15][CH:16]=2)[N:11]=[C:10]([N:18]2[CH2:19][CH2:20][NH:21][CH2:22][CH2:23]2)[N:9]=14-[(3S,4S)-(4-Hydroxytetrahydrofuran-3-yl)oxy]-2-(1-piperazinyl)quinazoline (cf. Example 16) (2.37 g) is dissolved in acetone (100 ml) with heating, and the mixture is filtered. The filtrate is concentrated to about 60 ml volume, and thereto is added acetic acid (495 mg), and the mixture is allowed to stand at room temperature. The precipitated crystals are separated by filtration to give 4-[(3S,4S)-(4-hydroxytetrahydrofuran-3-yl)oxy]-2-(1-piperazinyl) quinazoline monoacetate (2.37 g).
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