• The Korean Journal of Pesticide Science
• /
• v.5 no.3
• /
• pp.36-40
• /
• 2001

A series of new 2-N-benzyl-5-phenoxy-3-isothiazolone derivatives were synthesized and their in vitro antifungal activities against resistant Phytophthora capsici (RPC) & sensitive Phytophthora capsici (SPC) with metalaxyl fungicide have been measured. In addition, influence of substituted 5-phenoxy group on the -antifungal activities ($pI_{50}$) and the reactivity of substrates were investigated. From the results, reactivity of none substituted substrate showed tendency displaying orbital-controlled reaction. The substituents on the 5-phenoxy ring showed selective fungicidal activity between SPC and RPC. Especially, the 4-fluoro substituent, 6 in the RPC and 4-nitro substituent, 3 in SPC exhibited strongly selective antifungal activity among them. The activities on the SPC would depend largely on the optimal molar refractivity ($MR_{(opt.)}=7.37cm^3/mol$) whereas the activities on the RPC would depend largely on the optimal highest occupied molecular orbital energy ($HOMO_{(opt.)}=-9.2137e.v.$) and weak electron donating (${\sigma}<0$) group. And Free-Wilson analyses revealed that the antifungal activity against RPC depends on the methoxy and bromo-substituent and all of the substituents contribute to antifungal activities against SPC.

• The Korean Journal of Pesticide Science
• /
• v.5 no.4
• /
• pp.20-26
• /
• 2001

A series of new 2-benzoyl-3-phenyl-2,5-dihydroisoxazol-5-one, (A) and 3-phenyl-5-phenylcarbonyl-oxyisoxazole, (B) derivatives as substrates were synthesized and their quantitative structure-activity relationships (QSAR) analyses between the antifungal activities ($pI_{50}$) and physicochemical parameters of substituents onl the benzoyl group against resistant (RPC:95CC7303) and sensitive (SPC:95CC7105) Phytophthora blight (Phytophthora capsici,) were studied. The synthetic yield (%) and antifungal activities of (A) were higher than (B) and selectivities between the fungi were not showed. From the basis on the Hansch-Fujita analyses, the optimum width values ($(B_2)_{opt.}=ca.\;4.00{\AA}$) of the substituents on the benzoyl group were important factor in determining fungicidal activity against the two fungi. Influence of the substituents as electron withdrawing group on the fungicidal activity against RPC, but not for SPC. And tile bromo- and acetyl-substituents were contributed to higher antifungal activity against RPC and SPC from the results of Free-Wilson analyses.

• Applied Biological Chemistry
• /
• v.48 no.1
• /
• pp.82-88
• /
• 2005

3D QSAR studies for the fungicidal activities against resistive phytophthora blight (RPC; 95CC7303) and sensitive phytophthora blight (Phytopthora capsici) (SPC; 95CC7105) by a series of new 2-alkoxyphenyl-3-phenylthioisoindoline-1-one derivatives (X: A=propynyl & B=2-chloropropenyl) were studied using comparative molecular field analyses (CoMFA) methodology. The CoMFA models were generated from the two different alignment, atom based fit (AF) alignment and field fit (FF) alignment. The atom based alignment exhibited a higher statistical results than that of field fit alignment. The best models, A3 and A7 using combination fields of H-bond field, standard field, LUMO and HOMO molecular orbital field as additional descriptors were selected to improve the statistic of the present CoMFA models. The statistical results of the two models showed the best predictability of the fungicidal activities based on the cross-validated value $q^2\;(r^2_{cv.}=RPC:\;0.625\;&\;SPC:\;0.834)$, non cross-validated value $(r^2_{ncv.}=RPC:\;0.894\;&\;SPC:\;0.915)$ and PRESS value (RPC: 0.105 & SPC: 0.103), respectively. Based on the findings, the predictive ability and fitness of the model for SPC was better than that of the model for RPC. The fugicidal activities exhibited a strong correlation with steric $(66.8{\sim}82.8%)$, electrostatic $(10.3{\sim}4.6%)$ and molecular orbital field (SPC: HOMO, 12.6% and RPC: LUMO, 22.9%) factors of the molecules. The novel selective character for fungicidal activity between two fungi depend on the positive charge of ortho, meta-positions on the N-phenyl ring and size of hydrophilicity of a substituents on the S-phenyl ring.

• The Korean Journal of Pesticide Science
• /
• v.3 no.1
• /
• pp.29-36
• /
• 1999

A series of N-phenyl-O-phenylthionocarbamate derivatives were synthesized and determinated fungicidal activities in vitro against gray mold (Botrytis cinerea) and capsicum phytophthora blight (Phytophthora capsici) which showed resistance and sensitivity to benomyl and metalaxyl as systemic fungicides, respectively. The structure-activity relationship (SAR) was investigated by Free-Wilson analysis method and Hansch method. From the basis on the findings, the N-phenyl(X) groups had more contributions than O-phenyl(Y) groups did and ortho-substituents on the N-phenyl group showed high fungicidal activities. Especially, 4-cyano substituent, 2 as X-group showed 50% inhibition($pI_{50}=5.50$) of hyphae growth at 0.8ppm against resistance P. capsici (RPC) And hydroxyl substituents, 12 and 23 displayed the highest fungicidal activity against resistant B. cinerea (RBC), sensitive B. cinerea (SBC), and sensitive P. capsici (SPC). Antifungal activities of SPC were dependent upon molar refractivity (MR) constant and those of others relied on hydrophobic parameters (${\sigma}$ and logP). For increasing fungicidal activity against RPC and SBC, the optimum values of the sigma (${\sigma}$) and field(F) constants as electron withdrawing groups were 0.32 and 0.18, respectively.

• The Korean Journal of Pesticide Science
• /
• v.6 no.2
• /
• pp.72-79
• /
• 2002

3D-QSAR between fungicidal activitives ($pI_{50}$) against metalaxyl-sensitive (SPC: 95CC7105) or metalaxyl-resisitant (RPC: 95CC7303) isolate of phytophthora blight fungus (Phytophthora capsici), and a set of 3-phenylisoxazole (A) and 3-phenyl-2,5-dihydroisoxazole (B) derivatives as substrates were conducted using comparative molecular field analyses (CoMFA). The antifungal activities of (A) were generally higher than those of (B). And it is assumed that the most stable conformation of the active substrate was approximately planar from conformational search. The CoMFA models proved a good predictive ability and suggested that the electronic field of substrates were higher than hydropohobic field and steric field requirements for recognition forces of the receptor site. And the factors were strongly correlated (cross-validated $q^2>0.570$ & conventional $r^2>0.968$) with the fungicidal activitives. According to the CoMFA analyses, the selectivity factors for RPC suggested that the sterically bulky groups (C14 & C15) and electron withdrawing groups (C15 & C16) have to be introduced to the ortho, meta and para-position on the benzoyl moiety of substrates.