[CH2:1]([O:3][C:4]1[CH:9]=[CH:8][C:7]([NH2:10])=[C:6]([NH:11][CH:12]2[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]2)[CH:5]=1)[CH3:2].N[C:19](N)=[O:20].CCOC(C)=O>CC1C=CC(C)=C(C)C=1C>[CH:12]1([N:11]2[C:6]3[CH:5]=[C:4]([O:3][CH2:1][CH3:2])[CH:9]=[CH:8][C:7]=3[NH:10][C:19]2=[O:20])[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]1A mixture of 3.05 g of the oil obtained in step B) and 1.6 g of urea in 8 ml of 1,2,3,4-tetramethylbenzene is heated at 170°-180° C. for 1 hour 30 minutes. After cooling, it is taken up with AcOEt, washed with water and dried over sodium sulfate and the solvent is evaporated off under vacuum. The residue is taken up with hexane and the brown precipitate formed is filtered off. The precipitate is chromatographed on silica using a DCM/AcOEt mixture (50/50; v/v) as the eluent to give 1.33 g of the expected product, which was precipitated with isopropyl ether. M.p.=203° C.
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