Substituted N-Phenylpyrazine-2-carboxamides, Their Synthesis and Evaluation as Herbicides and Abiotic Elicitors

Abstract: The condensation of substituted pyrazine-2-carboxylic acid chlorides with ring-substituted anilines yielded five substituted pyrazine-2-carboxylic acid amides. Thesynthesis, and analytical, lipophilicity and biological data of the newly synthesizedcompounds are presented in this paper. The photosynthesis inhibition, antialgal activityand the effect of a series of pyrazine derivatives as abiotic elicitors on the accumulation offlavonoids in a callus culture of Ononis arvensis (L.) were investigated. The most activeinhibitor of the oxygen evolution rate in spinach chloroplasts was 6-chloro-pyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2, IC₅₀ = 51.0 μmol·L^-1). The highestreduction of chlorophyll content in Chlorella vulgaris was found for 5-tert-butyl-N-(4-chloro-3-methylphenyl)-pyrazine-2-carboxamide (3, IC₅₀ = 44.0 μmol·L^-1). The maximalflavonoid production (about 900%) was reached after a twelve-hour elicitation processwith 6-chloropyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2).