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Trangmolins A–F with an Unprecedented Structural Plasticity of the Rings A and B: New Insight into Limonoid Biosynthesis
Author(s) -
Li Wanshan,
Shen Li,
Bruhn Torsten,
Pedpradab Patchara,
Wu Jun,
Bringmann Gerhard
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201602230
Subject(s) - limonoid , stereochemistry , chemistry , ring (chemistry) , quantum chemical , biosynthesis , circular dichroism , crystallography , molecule , organic chemistry , enzyme
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‐1 H ‐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.