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A series of 17 simple 1-(2,4-dihydroxyphenyl) ethanones were synthesised, and their structures characterised by (1)H, (13)C NMR and ESI-MS. Their in vitro antifungal activities were evaluated against five phytopathogenic fungi including Glomerella cingulate, Botrytis cirerea, Fusarium graminearum, Curvularia lunata and Fusarium oxysporum f. sp. vasinfectum by the mycelial growth inhibition assay. Compounds 2g and 2h exhibited broad-spectrum inhibitory activity against the mycelial growth of the tested pathogens with IC50 values in the range of 16-36 μg/mL, and in particular being more active to G. cingulate, with IC50 values of 16.50 and 19.25 μg/mL, respectively, than the other pathogens. Preliminary SAR indicated that an α,β-unsaturated ketone unit of the alkyl chain of the compounds is the structure requirement for fungicidal action. The results suggested that 2g and 2h may be promising leads in the development of new antifungal agents.

Abstract:In order to establish an advanced structural-activity relationship (SAR) and to explore the feasibility of kakuol analogues with better anti-fungi activity, a series of 2-hydroxy-4,5-methylenedioxyaryl ketones were conveniently synthesized by the Friedel-Crafts acyl reaction, etherification reaction, reduction reaction and oximation reaction. Their structures characterized by 1 H and 13 C NMR and HRMS methods. Their in vitro antifungal activities were assayed. Most of the derivatives showed a remarkable in vitro activity, and some of them appeared significantly more effective than a commercial fungicide hymexazol as positive control. In particular compounds 2h and 2i, were found active with a IC 50 value of 3.1 mg/ml and 2.9 mg/ml against Glomerella cingulate, which suggested that 2-hydroxy-4,5-methylenedioxyaryl ketones might be a promising candidates in the development of new antifungal compounds. Compounds 2e, 5 and 6 also exhibited high antifungal activities on a wide range of organisms, which might be considered as leading compounds in the development of new antifungal compounds.