Polyhydroxylated bergamotane-type sesquiterpenoids from cultures of Paraconiothyrium sporulosum YK-03 and their absolute configurations

Eight undescribed polyhydroxylated bergamotane-type sesquiterpenoids with bicyclic, tricyclic and tetracyclic systems, namely sporulamides A-D, sporulosoic acids A-B and sporuloketals A-B, along with three known analogs were isolated from cultures of the marine mud-associated fungus Paraconiothyrium sporulosum YK-03. The chemical structures of these sesquiterpenoids were elucidated by the extensive spectroscopic techniques of NMR and HR-ESI-MS. Assisted by the X-ray crystallography analysis and electronic circular dichroism (ECD) spectroscopic calculation and comparison, their absolute configurations were established. Sporuloketals A-B represent two rare tetracyclic bergamotanes. It's the first time that ECD empirical rules have been successfully verified and applied for determining the absolute configurations of these bergamotane-type sesquiterpenoids.

Automated summary

Eight undescribed polyhydroxylated bergamotane-type sesquiterpenoids were discovered from a marine mud-associated fungus, and their chemical structures and absolute configurations were successfully determined. Among them, sporuloketals A-B represent two rare tetracyclic compounds. This study also validated the application of ECD empirical rules for determining the absolute configurations of these bergamotane-type sesquiterpenoids for the first time.