• The Korean Journal of Pesticide Science
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• v.10 no.1
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• pp.7-14
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• 2006

Three-dimensional quantitative structure-activity relationships (3D-QSARs) on the herbicidal activities against in-vitro pre-emergence rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) by new 5-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one derivatives were studied quantitatively using comparative molecular similarity indices analysis (CoMSIA) methodology. The optimized CoMSIA model(A5: $r^2_{cv.}=0.569$ & $r^2_{ncv.}=0.941$) for rice plant exhibited a good correlation with steric (31.6%) and hydrophobic (39.7%) factors of the substrate molecules, and the model (B4: $r^2_{cv.}=0.569$ & $r^2_{ncv.}=0.941$) for barnyardgrass exhibited a good correlation with electrostatic (46.7%) and H-bond acceptor field (30.8%), respectively. The predicted $R_1=SF_5,\;R_2=R_3=R_4=H(P1)$ substituent (Rice plant: $pI_{50}=4.84$ & Barnyardgrass: $pI_{50}=7.21$, ${\Delta}pI_{50}=2.37$) by the model (B4) not only exhibited to the highest herbicidal activity against barnyardgrass, but also exhibited to the highest selecticity between two plants.

• Applied Biological Chemistry
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• v.49 no.3
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• pp.238-242
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• 2006

The herbicidal activities against the pre-emergence of rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-gall) with changing substituents $(R_1-R_4)$ of new 5-benzofuryl-2-[1-(alkoxyimino) alkyl]-3-hydroxycyclohex-2-en-1-one derivatives as substrate molecules were studied quantitatively using comparative molecular field analyses (CoMFA). The optimized CoMFA models (rice plant: A5 & barnyard grass: B3) were derived from atom based fit alignment and a combination of CoMFA fields. The two models for herbicidal activity against two plants showed the best predictability and fitness ($q^2$>0.6 & ${r^2}_{ncv.}$>0.94) for the herbicidal activities. Also, CoMFA-HINT contour maps showed that the selective herbicidal activity between rice plant and barnyard grass depends on the hydrophobicity of $R_2\;and\;R_3$ groups in molecule. Therefore, it is expected that the herbicidal activity against barnyard grass will be improved by the introduction of the steric bulk small and hydrophobic group.

• The Korean Journal of Pesticide Science
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• v.7 no.2
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• pp.100-107
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• 2003

To improve the growth inhibitory activity against the shoot and root of rice plant (Oryza sativa L) and barnyard grass (Echinochloa crus-galli), a series of N-substituted phenyl-3,4-dimethylmaleimdes derivatives as substrates were synthesized and then their the inhibitory activities of protoporphyrinogen oxidase (1.3.3.4), protox were measured. The quantitative structure-activity relationships (QSAR) between structures and the inhibitory activities were studied quantitatively using the 2D-QSAR method. And also, molecular sharp similarity between the substrate derivatives and protogen, substrare of protox enzyme were studied. The activities of the two plants indicated that barnyard grass had a higher activity than the rice plant and their correlation relationships have shown in proportion for each. Accordingly, the results of SARs suggest that the electron donating groups as $R_2=Sub.X$ group will bind to phenyl ring because the bigger surface area of negative charged atoms in the substrate molecule derivatives may increase to the higher the activity against barnyard grass. Based on the molecular shape similarity, when the derivatives and protogen, subsbrate of protox enzyme were superimposed by atom fitting, the similarity indices (S) were above 0.8 level but the correlation coefficients (r) between S values and the activities showed not good.