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Structure and absolute configuration of hydroxy‐ bis ‐dihydrofarinosin from Encelia farinosa
Author(s) -
Ortega Alfredo R.,
OrtizPastraytzé,
Quijano Leovigildo,
BecerraMartínez Elvia,
OlmedoAguirre José O.,
JosephNathan Pedro
Publication year - 2017
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4554
Subject(s) - absolute configuration , chemistry , stereocenter , vibrational circular dichroism , stereochemistry , crystallography , crystal structure , circular dichroism , organic chemistry , enantioselective synthesis , catalysis
The structure of the dimeric eudesmanolide hydroxy‐ bis ‐dihydrofarinosin ( 1 ) from Encelia farinosa followed after contrasting their 1 H and 13 C NMR spectra with those of encelin ( 6 ), hydroxy‐ bis ‐dihydroencelin ( 3 ), and farinosin ( 4 ). Structure 1 was verified by single‐crystal X‐ray diffraction analysis, which further provided the stereochemistry of the hydroxy group at C‐4. Comparison of the experimental vibrational circular dichroism spectrum of its derived diacetate 2 with that calculated by density functional theory provided the absolute configuration, which resulted the same as that of its biogenetic precursor 4 . Evaluation of several chemical shift differences between the two eudesmanolide fragments of 1 and 3 allows also ascertaining the yet not reported absolute configuration of the C‐4 stereogenic center of 3 . Copyright © 2016 John Wiley & Sons, Ltd.
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