A reactive eremophilane and its antibacterial 2(1H)‑naphthalenone rearrangement product, witnesses of a microbial chemical warfare
S. Amand, M. Vallet, L. Guedon, G. Genta-Jouve, F. Wien, S. Mann, J. Dupont, S. Prado* and B. Nay*
Organic Letters 2017, in press, doi: 10.1021/acs.orglett.7b01788
Abstract: Two sesquiterpenes, 4-epi-microsphaeropsisin (1) and a dihydrofurano-2(1H)-naphthalenone (variabilone, 2) which represents a new skeleton, were isolated from endophytic fungus Paraconiothyrium variabile. Reactivity studies showed that eremophilane 1 is a precursor of 2 through acid-promoted methyl 1,2-migration and aromatization. An electrophilic intermediate of this transformation was intercepted by N-acetylcysteamine, a biomimetic nucleophile. Only compound 2 was antibacterial against endophytic bacterium Bacillus subtilis (coisolated with P. variabile), suggesting a role in the microbial competition in plants.