Synthesis and antifungal activity of six benzylic diamines

Six benzylic diamines were synthesised and examined for antifungal activity. Four of the compounds, KB 2, KB 4, KB 5 and KB 6, reduced radial growth of the oat leaf stripe pathogen Pyrenophora avenae, the largest reduction obtained with 25 μM KB 4, which reduced radial growth by 47%. Surprisingly, these four amines had no effect against infection of barley seedlings with the powdery mildew fungus Erysiphe graminis f.sp. hordei. Instead, two different amines, KB 1 and KB 3, reduced powdery mildew infection on barley. The greatest reduction was obtained with 25 μM KB 3, which reduced mildew infection by 69%. All of the amines which exhibited antifungal or fungicidal properties perturbed polyamine formation as measured by the incorporation of labelled ornithine into polyamines.