Studies of the New Herbicide KIH-6127. 4. Crystal Structure of KIH-6127 and Quantitative Structure-Activity Relationship of the Iminoxy Moiety of KIH-6127 Derivatives

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• 作者：Masatoshi Tamaru ; Jun Inoue ; Ryo Hanai ; and Shigehiko Tachikawa
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：1997
• 出版时间：July 1997
• 年：1997
• 卷：45
• 期：7
• 页码：2777 - 2783
• 全文大小：175K
• 年卷期：v.45,no.7(July 1997)
• ISSN：1520-5118

文摘

The crystal structure of the major isomer of KIH-6127 was investigatedby X-ray crystallographictechniques. The solid state structure and its conformation wereconfirmed as the E form. ThusKIH-6127 is mainly consistent with methyl2-[(4,6-dimethoxypyrimidin-2-yl)oxy]-6-[1-E-(methoxyimino)ethyl] benzoate (compound 1: Table 1).Further modifications of the iminoxy moiety tointroduce a variety of haloalkyl, haloalkenyl, and others were made,and the Z isomers of severalderivatives were prepared. The physicochemical properties of thesederivatives were measured,including their log P and K_d values.We tested their herbicidal activity against barnyard grassandtheir phytotoxicity to transplanted rice in flooded paddy conditions.We also studied the role of theiminoxy moiety, on the basis of the hypothesis that the difference inthe E/Z configurations of theiminoxy moiety determines their biological activity. However,clear differences in the herbicidalactivities were not observed between these isomer groups. EachZ isomer was more hydrophilicthan its E counterpart. To investigate this findingmore intensively in a single E/Z pair, thesurfacearea of each E/Z isomer of KIH-6127 wascalculated from the X-ray data for the KIH-6127 Eform.The Z conformation of the iminoxy moiety appears totake a more compact molecular conformation,resulting in the Z isomer having more hydrophilic surfacearea than the corresponding E isomer.QSAR studies focused on the iminoxy moiety. Both pre- andpost-emergence activities of thecompounds were well correlated with the square of the log Pvalue for both configurations of theiminoxy moiety. In other words, these configurations merelycontributed to the activity by way oftheir hydrophilicity. The difference between optimum logP values for pre- versus post-emergenceindicated that the optimum compound is more lipophilic for pre- thanfor post-emergence activity.Phytotoxity against rice also correlated well with theK_d value. Thus stronger soil adsorptionofthe compounds provides higher safety for rice. On the basis ofthose QSAR studies, compound 1was selected as the optimal compound for development as a commercialherbicide.Keywords: Methyl2-[(4,6-dimethoxypyrimidin-2-yl)oxy]-6-[1-E-(methoxyimino)ethyl]benzoate; KIH-6127; Pyriminobac-methyl; herbicide; barnyard grass; ALS;QSAR