a/f-Dehydrocurvularin and Curvularin from A ltem aria cinerariae

The genus Alternaria Nees ex Fr. (Dematiaceae) contains a number of species pathogenic to econom­ ically important crop plants [1]. Perhaps not unre­ lated to this is the fact that the Alternaria are a rich source of biologically active secondary metabolites [2], several of which are phytotoxic [3]. In fact, with the possible exception of the genus H elm inthosporium Link ex Fries, more phytotoxins are known to be produced by the Alternaria than any other fungal genus [4-6]. They include toxins both hostspecific (eg. phytoaltamarin A [3]) and non hostspecific (eg. zinniol [7]) in their action. A lternaria cinerariae Hori and Enjoji (syn. Alternaria senecionis Neergaard) [8] is a pathogen of the ornamental cineraria (Senecio cruentus (Masson) DC. (Compositae)). The fungus causes damping-off of seedlings and may be responsible for a severe leaf-spot on cineraria [1, 9]. A strong attack on lettuce has also been observed during infection experiments [1], Secondary metabolite production by this fungus was investigated as part of a screening process of phytopathogenic fungi in search of compounds with potential for use as herbicides. The fungus was maintained on potato dextrose agar and grown in shake culture for periods of two to three weeks. After incubation for fifteen days CHC13 extracts of the culture filtrate, when dried in vacuo and taken up in 50% EtOH, yielded a pale yellow crystalline product as needles. Recrystalliza­ tion from petrol-EtOAc afforded pale yellow plates (mp. 224°), the molecular formula of which was