20-Nor-Isopimarane Epimers Produced by Aspergillus wentii SD-310, a Fungal Strain Obtained from Deep Sea Sediment

摘要

Four new uncommon 20-nor-isopimarane diterpenoid epimers, aspewentins I?L ( 1 – 4 ), together with a new methylated derivative of 3 , aspewentin M ( 5 ), were isolated from the deep sea sediment-derived fungus Aspergillus wentii SD-310. The very similar structures of these epimers made the separation and purification procedures difficult. The structures of compounds 1 – 5 were illustrated based on spectroscopic analysis, and the absolute configurations of compounds 1 – 5 were unambiguously determined by the combination of NOESY, time-dependent density functional (TDDFT)-ECD calculations, and X-ray crystallographic analysis. These metabolites represented the rare examples of 20-nor-isopimarane analogues possessing a cyclohexa-2,5-dien-1-one moiety. These compounds were tested for antimicrobial activities against human and aquatic pathogenic bacteria, as well as plant-pathogenic fungi. While compounds 1 and 2 exhibited inhibitory activities against zoonotic pathogenic bacteria such as Escherichia coli , Edwardsiella tarda , Vibrio harveyi , and V. parahaemolyticus , compound 5 showed potent activity against the plant pathogen Fusarium graminearum .