28,29-Di-nor-triterpenoid and indole diketopiperazine alkaloids from the endophytic fungus Aspergillus versicolor

Five previously undescribed compounds, including one di- nor -lanostanoid aspverslanostane A ( 1 ), one indole diketopiperazine (indole DKP) alkaloid aspversamide A ( 2 ), and three itaconic acid derivatives asperitaconic acids D–F ( 13 – 15 ), along with 15 previously identified compounds, are isolated from the endophytic fungus Aspergillus versicolor HYQZ-324. The structures of compounds are elucidated via comprehensive spectroscopic analyses and electronic circular-dichroism calculations. Aspverslanostane A ( 1 ) represents the first example of a naturally occurring triterpene both with the 28- and 29-methyl groups demethylated. Aspversamide A ( 2 ) exhibits a distinctive skeletal structure of indole DKPs, characterised by an additional benzofuranone moiety at C-8. The compounds selected are subjected to anti-bacterial activity assays against eight clinically resistant bacteria, and none of the compounds exhibit satisfactory activity.