title: Trangmolins A-F with an Unprecedented Structural Plasticity of the Rings A and B: New Insight into Limonoid Biosynthesis.
abstract: The absolute stereostructures of trangmolins A-F (1-6), limonoids with three new and one known topologies of the rings A and B, were unambiguously determined by NMR spectroscopic investigations, single-crystal XRD analysis, and quantum-chemical electronic circular dichroism calculations. Compounds 1-3 contain a hexahydro-1H-inden-4-one motif, compound 4 comprises a hexahydro-2,6-methanobenzofuran-7-one cage, and compound 5 consists of a hexahydro-2H-2,8-epoxychromene scaffold. The C1-C30 linkage in 1-3 and the C3-C30 connection in 4 form two unprecedented types of ring A/B-fused carbobicyclic cores: viii and ix. The oxidative cleavage of the C2-C3 bond in 5 and heterocyclization in 4 and 5 constitute the unprecedented tricyclic 6/6/5 ring A/B(1) /B(2) - and 6/5/6 ring A(1) A(2) /B-fused topologies, respectively, which are uncovered, for the first time, in the construction of limonoid architectures. The diverse cyclization patterns of 1-6 reveal an unparalleled structural plasticity of rings A and B in limonoid biosynthesis.
authors.affiliation: Marine Drugs Research Center, College of Pharmacy, Jinan University, 601 Huangpu Avenue West, Guangzhou, 510632, P.R. China.
authors.forename: Wanshan
authors.initials: W
authors.lastname: Li
authors.affiliation: Marine Drugs Research Center, College of Pharmacy, Jinan University, 601 Huangpu Avenue West, Guangzhou, 510632, P.R. China. shenli6052@sina.com.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Institute of Organic Chemistry, University Würzburg, Am Hubland, Würzburg, 97074, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Bruhn
authors.affiliation: Aquatic Animal Health Management Research Unit, Department of Marine Sciences, Faculty of Sciences and Fishery Technology, Rajamangala University of Technology Srivijaya, Trang Campus, Sikao District, Trang Province, 92150, Thailand.
authors.forename: Patchara
authors.initials: P
authors.lastname: Pedpradab
authors.affiliation: Marine Drugs Research Center, College of Pharmacy, Jinan University, 601 Huangpu Avenue West, Guangzhou, 510632, P.R. China. wwujun2003@yahoo.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.affiliation: Institute of Organic Chemistry, University Würzburg, Am Hubland, Würzburg, 97074, Germany. bringmann@chemie.uni-wuerzburg.de.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Bringmann
mesh_terms: D002942:Circular Dichroism; D036701:Limonins / Q000096:biosynthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure
chemical_list: D036701:Limonins
keywords: biosynthesis; configuration determination; mangrove limonoids; natural products; structure elucidation