Issue 13, 2016

Solution-state conformations of natural products from chiroptical spectroscopy: the case of isocorilagin

Abstract

Isocorilagin, the α-anomer of the ellagitannin corilagin, has been frequently reported in the literature as a constituent of various plant species. Its identification is based mainly on the smaller value for the coupling constant of its anomeric proton when compared to that of corilagin. A careful investigation of the corilagin structure in both methanol and DMSO solutions using NMR, electronic and vibrational CD, and DFT and MD calculations confirmed that isocorilagin is the result of a solvent-induced conformational transition of corilagin, rather than its diastereoisomer. Corilagin changes from B1,4 and oS5 conformations of the β-glucose core in DMSO-d6 to an inverted 1C4 conformation in methanol-d4, which accounts for NMR observables attributed to the alleged α-anomer. This misassignment reinforces the risks of relying upon a single technique for structural elucidation and stereochemical analysis of complex natural products, especially those containing saccharide moieties.

Graphical abstract: Solution-state conformations of natural products from chiroptical spectroscopy: the case of isocorilagin

Supplementary files

Article information

Article type
Paper
Submitted
08 Jan 2016
Accepted
25 Feb 2016
First published
25 Feb 2016

Org. Biomol. Chem., 2016,14, 3369-3375

Solution-state conformations of natural products from chiroptical spectroscopy: the case of isocorilagin

R. F. Sprenger, S. S. Thomasi, A. G. Ferreira, Q. B. Cass and J. M. Batista Junior, Org. Biomol. Chem., 2016, 14, 3369 DOI: 10.1039/C6OB00049E

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