Shikimerans B―D: New polyketides from the endophytic fungus Chaetomium sp. FZ-4 of Aconitum carmichaelii Debx

• Two previously undescribed and one new natural polyketides were isolated. • All compounds (except 4 , 6 and 7 ) were firstly reported from Chaetomium sp. • Compound 1 − 4 were identified as derivatives of shikimic acid. Two undescribed shikimic acid derivatives named shikimerans B and C ( 1 and 2 ), one new natural compound shikimeran D ( 3 ), as well as five known compounds 4 − 8 were obtained from the EtOAc extract of the endophytic fungus Chaetomium sp. FZ-4. Their structures were determined by the NMR spectroscopy and HRESIMS examination, while the absolute configurations of compounds 1 − 3 were clarified based on the electronic circular dichroism (ECD) experiment. These new compounds enriched the structural diversity of shikimic acid analogues and also expanded the chemical diversity of the metabolites of Chaetomium sp..