Chlorosphaeropsidone and Epichlorospaeropsidone, Two New Chlorinated Dimedone Methyl Ethers Isolated from Liquid Cultures of «Sphaeropsis sapinea» f. sp. «cupressi»

Abstract

Two new dimedone methyl ethers, named chlorosphaeropsidone and epichlorosphaeropsidone were isolated from the culture filtrates of Sphaeropsis sapinea f. sp. cupressi, the causal agent of a canker of Italian cypress (Cupressus sempervirens L.). The same fungus also produced various phytotoxic metabolites: three pimarane diterpenes (sphaeropsidins A, B and C) and two dimedone methyl ethers (sphaeropsidone and episphaeropsidone). Chlorosphaeropsidone and epichlorosphaeropsidone were characterized using chemical and spectroscopic methods as two 6-chloro-4,5-dihydroxy-3-methoxycyclohex-2-en-1-ones epimers at C-6. Their relative and absolute configurations were established by NMR, X-ray analysis and circular dichroism. Assayed on host plants they did not show phytotoxic activity. Comparison with other sphaeropsidones suggested that this might result from opening of the epoxy ring.