Chenopodolans A–C: Phytotoxic furopyrans produced by Phoma chenopodiicola, a fungal pathogen of Chenopodium album

Abstract

Three tetrasubstituted furopyrans, named chenopodolans A-C, were isolated together with the well known fungal metabolite (-)-(R)-6-hydroxymellein from the liquid culture of Phoma chenopodiicola, a fungal pathogen proposed for the biological control of Chenopodium album, a common worldwide weed of arable crops. The structures of chenopodolans A-C were established by spectroscopic and chemical methods as 2-(3-methoxy-2,6-dimethyl-7aH-furo[2,3-b]pyran-4-yl)-butane-2,3-diol, 1-(3-methoxy-2,6-dimethyl-7aH-furo[2,3-b]pyran-4-yl)ethanol and 3-methoxy-2,6-dimethyl-4-(1-methylpropenyl)-7aH-furo[2,3-b]pyran, respectively. The absolute configuration R to the hydroxylated secondary carbon (C-11) of the side chain at C-4 of chenopodolan A was determined by applying an advanced Mosher's method. Assayed by leaf puncture on host and non-host weeds chenopodolans A and B, and the 11-O-acetylchenopodolan A showed a strong phytotoxicity. These results showed that the nature of the side chain attached to C-4 is an important feature for the phytotoxicity. A weak zootoxic activity was only showed by chenopodolan B.