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.