Novel antifungal polyene amides from the myxobacterium Cystobacter fuscus: isolation, antifungal activity and absolute structure determination

Three new unstable metabolites, (6E,10Z)-2′-O-methylmyxalamide D (), 2′-O-methylmyxalamide D () and (6E)-2′-O-methylmyxalamide D () were isolated from the myxobacterium Cystobacter fuscus. The planar structures were elucidated by spectroscopic analyses to be geometrical isomers of a polyene amide related to a myxobacterial metabolite, myxalamide D (). Their absolute stereochemistry was determined by synthesis of degradation products. Antifungal activities of as well as their acetates were evaluated against the phythopathogenic fungus Phythopthora capsici.