Studies On The Synthesis And Biological Activities Of Substituted Ureas Including Triazole And Thiodiazole

Plant growth regulator is a kind of organic compound with plant hormone function synthesized by artificial methods. In order to seek good plant growth regulator, we have modified the main structure of ureas by Bioisosterism Principles and Substructure Link Wory and synthesized 34 substituted ureas including 33new compounds and one old compound.By consulting concerned literatures, we reviewed the biological activities of triazole , 1,3,4-thiodiazole, acyl ureas and ureas, and the synthetical methods of acyl ureas and ureas. Target compounds have been synthesized by condensation of the amino heterocycle with isocyanates in absolutely anhydrous and aprotic solvent. Reaction of Acyl isocyanate with 5-amino?H-1,2,4 -triazolyl-3 -carboxylic acid in absolutely anhydrous DMF gave 24 new acyl urea compounds . At the same time, 10 substituted ureas including one old compound were synthesized from aryl carboxylic acid by Curtius rearrangement, not isocyanates but carbonyl azides heated with thiodiazole derivatives. IR, 1H NMR, MS and elementary analysis confirm their structures. Physic-chemical constant, spectrum properties and synthesis condition of the target compounds was reported firstly. We also analyzed the by-product that formed in the reaction and the possible mechanism was offered. The main structures of the target compounds are listed as follows. I .N-5-(lH-l,2,4-Triazole-3-carboxyl)-N' -aryl acyl ureas II. N-5-(lH-l,2,4-triazole-3-carboxyl)-N'-aroxyl acetyl ureas EL N-(substituted phenyl)-N'-(l,3,4-Thiodiazolyl-2-)ureas The plant growth regulating activity was tested by the method of cucumber cotyledon expansion, taking root and wheat sheath on the target compounds. Preliminary results indicate that many of acyl ureas exhibited higher activity on auxin , especially for those with chloride substituted on the phenyl ring .The auxin activity of the compound I f and I g was close to that of β - indolyl acetic acid. The same activity of the compound I b and I d was higher than that of the β- indolyl acetic acid. The same activity of the compound I b and I d was higher than that of the # -indolyl acetic acid, while they have little cytokinin activity , But compound II f can promote root growing .In III series of compounds, auxin activity was lower, cytokinin activity of the compound IIIj was much better than that of kinetin in promoting cotyledon.Quantum mechanics calculations were performed on 12 compounds of series I. Qualitative relationship was found between the structures and activity of these compounds, by means of theoretical calculations and analysis on composition of frontier orbital, atomic charges and characteristic geometrical parameters. Theoretical analysis indicted that the activity of these compounds may be dominated by contribution of the atoms at the position of 3, 4 and 5 to HOMO. Net atomic charge held by these atoms, dihedral angels between phenyl ring and heterocycle and compositions of HOMO are also factors which may affect the biological activity of these compounds. This conclusion can qualitatively give the Structure-Activity relationship for the compounds I b, I c, I f, I g and 11, which have good biological activity.