Enantioselective Synthesis of Pyrazolo[3,4- b ]pyridone Derivatives with Antifungal Activities against Phytophthora capsici and Colletotrichum fructicola .

A chiral NHC-catalyzed [3 + 3] cycloaddition reaction is developed for the efficient synthesis of pyrazolo[3,4- b ]pyridones in generally excellent yields and optical purities. The R , S , and racemic forms of these molecules are systematically studied via in vitro tests that detect antifungal activity against Phytophthora capsici and Colletotrichum fructicola . Chiral compounds ( R )- 3i , ( R )- 3j , and ( R )- 3p are identified to have excellent inhibitory effects against P. capsici and C. fructicola .