1980 Volume 25 Issue 1 Pages 34-41
Herbicidal activity of N-substituted phenylcarbamoylβ-alanine derivatives, i. e., N-alkyl-N-(substituted phenylcarbamoyl)β-alanines (Str. 1) and their ring closed compounds, 1-alkyl-3-(substituted phenyl) dihydrouracils (Str. 2), were evaluated in Petri dish test and pot test. The significant correlation was recognized by comparing the herbicidal activities [pI50(s) by the Petri dish test; pI50(f), log%(F), log%(T) by the pot tests] with the hydrophobic parameter (log P). Then the herbicidal activity of the above mentioned compounds was analyzed in term of the parameter log P using the FUJITA-HANSCH approach.
(1) Herbicidal activities of N-alkyl-N-(3, 4-dichlorophenylcarbamoyl)β-alanine methyl esters (Str. 1-1) were regressed highly significantly into the two-dimentional single parameter equations. And the optimum log P (log Po) of the Str. 1-1 was fluctuating in the range of 3.2-3.4. Alkyl moiety which gave the log Po was iso-propyl group. Herbicidal activities of N-alkyl-N-(4-chlorophenylcarbamoyl) β-alanine methyl esters (Str. 1-2) and 1-alkyl-3-(4-chlorophenyl) dihydrouracils (Str. 2-1) were regressed into one-dimentional equations by the results of Petri dish test or into two-dimentional (-like) equations by the results of pot tests.
(2) Among the benzene ring substituents, the 3, 4-dichloro compounds showed the highest activity. Effect of the benzene ring substituents of 1-methyl-3-(substituted phenyl) dihydrouracils (Str. 2-2) was higher than those of N-methyl-N-(substituted phenylcarbamoyl)β-alanines (Str. 1-4) and the methyl esters of them (Str. 1-3).
(3) The relationship between the opened (Str. 1-3, Str. 1-4) and the related ring-closed (Str. 2-2) compounds was also appreciated. Activity order of those groups consistent with the hydrophobicity order.
(4) The relationship between the results of Petri dish test and those of pot tests was observed on the Str. 1-1, Str. 1-3, Str. 2-1 and Str. 2-2.
(5) As the compound having the highest activity, 3-(3, 4-dichlorophenyl)-1-iso-propyl dihydrouracil was assumed.
