Title
Trangmolins A–F with an Unprecedented Structural Plasticity of the Rings A and B: New Insight into Limonoid Biosynthesis
Author
Wanshan Li, Li Shen, Torsten Bruhn, Patchara Pedpradab, Jun Wu, Gerhard Bringmann
Year
2016
Journal
Chemistry A European Journal
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 C1C30 linkage in 1–3 and the C3C30 connection in 4 form two unprecedented types of ring A/B-fused carbobicyclic cores: viii and ix. The oxidative cleavage of the C2C3 bond in 5 and heterocyclization in 4 and 5 constitute the unprecedented tricyclic 6/6/5 ring A/B1 /B2 - and 6/5/6 ring A1 A2 /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. I
Instrument
J-715
Keywords
Circular dichroism, Absolute configuration, Pharmaceutical