Many isolates of Trichodermaspp. have been shown to produce 10-20 unstable metabolites, characterized by the presence of an isocyano group, by a recently described analytical method. The purification of these metabolites can be followed by this method and in this way 4-hydroxy-8-isocyano-loxaspiro[4~4]cyclonon-8-en-2-one 9,t 1 - (2,3-epoxy-? - hydroxy-3-isocyanocyclopent-4-enyl)ethanol 13, and 1 - (1,4,5-trihydroxy-2-isocyanopent-2-enyl)ethanol 11 have been isolated and characterized. The presence of an isomer of methyl 3- (1,5-dihydroxy-3-isocyanocyclopent-3-enyl) prop-2-enoate 6, previously reported has been confirmed.