Synthesis of 2-amino-6-oxocyclohexenylsulfonamides and their activity against Botrytis cinerea.

BACKGROUND: With the objective of exploring the fungicidal activity of 2-oxocyclohexylsulfonamides (2), a series of novel 2-amino-6-oxocyclohexenylsulfonamides (6 to 23) were synthesised, and their fungicidal activities against Botrytis cinerea Pers. were evaluated in vitro and in vivo. RESULTS: The compounds were characterised by IR, 1H NMR and elemental analysis. Bioassay results of mycelial growth showed that compounds 6 to 23 had a moderate antifungal activity against B. cinerea. N-(2-methylphenyl)-2-(2-methylphenylamino)-4,4-dimethyl-6-oxocyclohexenylsulfonamide (13) and N-(2-chlorophenyl)-2-(2-chlorophenylamino)-6-oxocyclohexenylsulfonamide (21) showed best antifungal activities, with EC50 values of 8.05 and 10.56 µg mL(-1) respectively. Commercial fungicide procymidone provided an EC50 value of 0.63 µg mL(-1) . The conidial germination assay showed that most of compounds 6 to 23 possessed excellent inhibition of spore germination and germ-tube elongation of conidia of B. cinerea. For in vivo control of B. cinerea colonising cucumber leaves, the compound N-cyclohexyl-2-(cyclohexylamino)-4,4-dimethyl-6-oxocyclohexenylsulfonamide (19) showed a better control effect than the commercial fungicide procymidone. CONCLUSION: The present work demonstrated that 2-amino-6-oxocyclohexenylsulfonamides can be used as possible new lead compounds for further developing novel fungicides against B. cinerea.

Synthesis, fungicidal activity, and structure-activity relationship of 2-oxo- and 2-hydroxycycloalkylsulfonamides.

To explore new potential fungicides, a series of novel compounds, including 11 2-oxocycloalkylsulfonamide (3) and 21 2-hydroxycycloalkylsulfonamide (4) derivatives, were synthesized and their structures were confirmed by (1)H nuclear magnetic resonance (NMR), infrared (IR), and elemental analysis. The results of the bioassay showed that the compounds 3 and 4 possessed excellent fungicidal activity against Botrytis cinerea Pers. both in vitro and in vivo. The fungicidal activity of the compounds with 7- or 8-membered rings is better than those with 5-, 6-, or 12-membered rings. According to the results of the mycelium growth rate test, the EC50 values of the compounds 3C, 4C, 3D, and 4D were 0.80, 0.85, 1.22, and 1.09 µg/mL, respectively, and similar to or better than commercial fungicide procymidone. The bioassay results of spore germination indicated that most of the compounds exhibited obvious inhibitory effects against B. cinerea and the inhibition rates of 2-oxocycloalkylsulfonamides were higher than 2-hydroxycycloalkylsulfonamides, among them. The EC50 values of compounds 3A, 3B17, 3E, and 4A were 4.21, 4.21 3.24, and 5.29 µg/mL, respectively. Those compounds containing 5- or 6-membered rings showed better activity than those containing 7-, 8-, or 12-membered rings. Furthermore, the results of the pot culture test showed that almost all of the compounds had effective control activity in vivo and 2-hydroxycycloalkylsulfonamides were obviously superior to 2-oxocycloalkylsulfonamides. The compounds 3E, 4C and 4D presented higher control efficacy than procymidone and pyrimethanil against gray mold disease on cucumber plants.