新規グリコールベンジルエーテル系除草剤 : 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyran誘導体の除草活性 Novel glycol benzyl ether herbicides : Herbicidal activity of 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyran derivatives(PART I (IN ENGLISH))

新規グリコールベンジルエーテル系除草剤3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyrans (TFBs)の構造活性相関を解明した.ノビエに対する除草活性とイネに対する薬害はTFB環の3位のベンジルオキシ基の置換基により変動した.TFB環の3位にシクロヘキシルメチル基やベンゾイル基等のベンジル基以外の置換基を導入した場合,除草活性は低減した.TFB環の5位にメチル基を導入した場合,5-(S)-体のほうが5-(R)-体よりも強い除草活性を示した.5位に(S)-メチル基を導入した場合,除草活性は無置換体と比較して大幅に向上したものの,イネに対する薬害は悪化した.TFB環のベンゼン環をチオフェン環,フラン環に変換しても高い除草活性を示し,チオフェン変換体は今回合成した化合物の中で最も高い除草活性を示し,イネに対する薬害も軽微であった.TFB環の5位へのgem-ジメチル基導入体の合成時の副生成物として得られた2,6-dioxabicyclo[3,3,0]octaneも高い除草活性を示した.

The structure-activity relationship of novel glycol benzyl ether herbicides, 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyrans (TFBs), was elucidated. Herbicidal activity against Echinochloa crus-galli and rice injury varied with substituents of the benzyloxy group at C-3. When substituents other than the benzyloxy group, such as the cyclohexylmethyloxy group or the benzoyloxy group, were introduced, the herbicidal activity of TFBs was reduced. Introduction of an (S)-methyl group at C-5 increased herbicidal activity but aggravated rice injury. When comparing the herbicidal activity of two stereoisomers, the 5-(S)-isomer showed stronger herbicidal activity than the 5-(R)-isomer. Even when the benzene ring of the fused ring system of TFB was replaced by thiophene or furan, high herbicidal activity was manifested. In particular, TFB partly replaced by thiophene showed the highest herbicidal activity among all compounds examined in this study, with slight injury to rice plants. The 2,6-dioxabicyclo[3,3,0]octane derivative, produced as a by-product, also showed high herbicidal activity.