Koningipyridines A and B, two nitrogen-containing polyketides from fungus Trichoderma koningiopsis SC-5

Zhenxing Zou^1*, Weiwei Peng¹, Qi Huang¹, Xin Ke¹, Wen-Xuan Wang¹, Yan Chen¹, Zihuan Sang¹, Chen Chen¹, Siyu Qin¹, Yuting Zheng¹ and Haibo Tan²

• ¹Central South University, China
• ²South China Botanical Garden, Chinese Academy of Sciences (CAS), China

Two novel koninginin derivatives, koningipyridines A (1) and B (2), together with four known compounds (3-6) were isolated from the EtOAc extract of the endophytic fungus Trichoderma koningiopsis SC-5. Among them, koningipyridine A featured an unprecedented pentacyclic ketal skeleton with the formation of a fascinating 6/6/5/6/5 fused ring system and shared a characteristic pyridine core, which represents the first example of nitrogen-containing koninginin type natural product. Moreover, the koningipyridine B was evidenced to be the first member in koninginin family sharing a unique 6/6/5 dihydropyridine skeleton, and it was chemo-logically suggested to be critical biosynthetic precursor of koningipyridine A. Their structures and absolute configurations were extensively established on the basis of NMR, HRESIMS, 13C NMR, and theoretical electronic circular dichroism (ECD) calculations. Moreover, all isolates were evaluated for their antimicrobial and cytotoxic activities, and all compounds showed weak activities against a panel of human cancer cell lines including A549, Hela, and HepG2.