title: Identification of Oxaphenalenone Ketals from the Ascomycete Fungus Neonectria sp.
abstract: Neonectrolides B-E (4-7), four new oxaphenalenone ketals incorporating the new furo[2,3-b]isochromeno[3,4,5-def]chromen-11(6aH)-one skeleton, were isolated from the fermentation extract of the ascomycete fungus Neonectria sp. in an in-depth investigation guided by HPLC fingerprint and a cytotoxicity assay. The previously identified oxaphenalenone spiroketal neonectrolide A (1) and its putative biosynthetic precursors (2 and 3) were also reisolated in the current work. The structures of 4-7 were primarily elucidated by interpretation of NMR spectroscopic data, and the absolute configurations were deduced by electronic circular dichroism calculations. Compound 6 showed cytotoxic effects against four of the six human tumor cell lines tested. Biosynthetically, compounds 4-7 could be derived via the Diels-Alder reaction cascades starting from derivatives of the co-isolated metabolites 2 and 3.
authors.affiliation: †State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Jinwei
authors.initials: J
authors.lastname: Ren
authors.forename: Shubing
authors.initials: S
authors.lastname: Niu
authors.affiliation: §Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: ⊥Analytical and Testing Center, Beijing Normal University, Beijing 100875, People's Republic of China.
authors.forename: Zhufeng
authors.initials: Z
authors.lastname: Geng
authors.affiliation: †State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Xingzhong
authors.initials: X
authors.lastname: Liu
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Che
mesh_terms: D001203:Ascomycota / Q000737:chemistry*; D045744:Cell Line, Tumor; D002681:China; D002851:Chromatography, High Pressure Liquid; D004354:Drug Screening Assays, Antitumor; D005663:Furans / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D013141:Spiro Compounds / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D005663:Furans; D013141:Spiro Compounds; C578822:neonectrolide A