Discovery of Novel Cinnamide Fungicidal Leads with Optical Hydroxyl Side Chain.

In order to overcome the resistance of phytopathogens to commercial fungicides, a series of optical 2-methyl-2,3-diol-5-pentyl-based cinnamamide derivatives were rationally designed, synthesized, characterized, and evaluated for their in vitro and in vivo fungicidal activities. The bioassay results indicated that the EC 50 (concentration for 50% of maximal effect) values of ( R )- 11f , ( R )- 11m , ( S )- 11m and ( R )- 11n were 0.16, 0.28, 0.41 and 0.47 µg/mL in the in vitro evaluation against Sclerotinia sclerotiorum , respectively, while compounds ( R )- and ( S )- 11i , ( R )- and ( S )- 11j exhibited excellent in vivo fungicidal activity against Pseudoperonspera cubensis with inhibition rates of 100% at 400 μg/mL. These findings supported the idea that optical 2-methyl-2,3-diol-5-pentyl-containing cinnamamides ( R )- and ( S )- 11i , ( R )- and ( S )- 11j with 2-chloro-4-trifluoromethyl aniline and 2-(4-chlorophenyl) aniline showed excellent in vivo fungicidal activity against S. sclerotiorum and P. cubensis and were promising fungicide candidates.