Chemical reactivity of the toxin oosponol from Gloeophyllum abietinum with nucleophilic agents.

It is shown that contrary to most isocoumarins the antibiotic compound oosponol from the fungus Gloeophyllum abietinum reacts instantaneously with nucleophilic agents like thiol compounds. The reason for this high reactivity is due to the vinylogous acid anhydride character of the compound which is produced by a single oxidation step of the non toxic biological precursor oospoglycol. One must assume that reactions of oosponol with HS-groups of polypeptides form the basis for its toxicity. The ring-opening reactions were studied in detail with the synthetic analogue 4-acetyl-isocoumarin. The structures of some reaction products have been analysed mainly with H-1 and C-13 NMR spectroscopy.