SYNTHESIS AND POLLEN SUPPRESSANT ACTIVITY OF PHENYLCINNOLINE-3-CARBOXYLIC ACIDS

A series of 1,4-dihydro-4-oxo-1-phenylcinnoline-3-carboxylic acids were prepared, and their pollen suppression activity on wheat (Triticum aestivum L.) was evaluated. The substituents and substitution pattern on the cinnoline ring were varied systematically with particular interest shown to the substituent at C-5. Significant pollen suppressant activity is described for analogues bearing a heteroatom substituent, such as fluorine or alkoxy, at C-5 of the cinnoline ring. Compounds bearing an amino substituent showed little or no activity, and compounds with methyl substitution at C-5 were inactive. Variation in the substituents on the phenyl ring was carried out in parallel and was found to modulate the activity of the compounds. In addition to the pollen suppression activity measurement, the phytotoxic effect of the compounds on wheat was observed as chlorosis, plant height reduction, or necrosis. However, no effect on seed quality was seen. The leading compounds for use as chemical hybridization agents are members of the alkoxy series containing less than four carbon atoms, which have the best balance of high sterility and low phytotoxicity.