C(O[C:4]([CH:6]1[CH2:11][NH:10][C:9]2[CH:12]=[CH:13][CH:14]=[CH:15][C:8]=2[O:7]1)=[O:5])C.[CH2:16]([NH2:20])[CH2:17][CH2:18][CH3:19]>>[CH2:16]([NH:20][C:4]([CH:6]1[CH2:11][NH:10][C:9]2[CH:12]=[CH:13][CH:14]=[CH:15][C:8]=2[O:7]1)=[O:5])[CH2:17][CH2:18][CH3:19]A mixture of 600 mg of 2(R,S)-ethoxycarbonyl-3,4-dihydro-2H-1,4-benzoxazine (Example 16)) and 1.2 ml of butylamine is stirred at 60° C. for 1 h. The reaction mixture is concentrated and the residue is purified directly by means of FC over 50 g of silica gel with a 20:1 mixture of methylene chloride and diethyl ether as the mobile phase. 2(R,S)-Butylaminocarbonyl-3,4-dihydro-2H-1,4-benzoxazine is obtained: Rf (20:1-mixture of methylene chloride and diethyl ether)=0.32.
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