Mode of action studies showed that 5-methyl-N,N-bis[6-(trifluoromethyl)pyridin-3-yl]pyridin-2-amine (4), a representative from a new class of herbicidal tris-pyridyl amines, is an inhibitor of cellulose biosynthesis (CB). The compound undergoes an oxidative photocyclization, when exposed to UV-B light (300–340 nm) in the presence of oxygen, to give a new class of herbicidal pyrrolodipyridines. These compounds are potent inhibitors of the herbicide target enzyme phytoene desaturase and no longer inhibit CB.

中文翻译：

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纤维素生物合成抑制剂向八氢番茄红素去饱和酶抑制剂的光化学转化

作用模式研究表明，5-甲基-N,N-bis[6-(trifluoromethyl)pyridin-3-yl]pyridin-2-amine ( 4 ) 是一类新型除草剂三吡啶胺的代表，纤维素生物合成（CB）的抑制剂。当在氧气存在下暴露于 UV-B 光（300-340 nm）时，该化合物会发生氧化光环化，从而产生一类新的除草吡咯并二吡啶。这些化合物是除草剂靶酶八氢番茄红素去饱和酶的有效抑制剂，不再抑制 CB。