Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

The absolute configuration (AC) of the naturally occurring ocimenes (−)‐(3S,5Z)‐2,6‐dimethyl‐2,3‐epoxyocta‐5,7‐diene (1) and (−)‐(3S,5Z)‐2,6‐dimethylocta‐5,7‐dien‐2,3‐diol (2), isolated from the essential oils of domesticated specimens of Artemisia absinthium, followed by vibrational circular dichro...

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Bibliographic Details
Published in:Chirality (New York, N.Y.) N.Y.), 2017-11, Vol.29 (11), p.716-725
Main Authors: Julio, Luis F., Burgueño‐Tapia, Eleuterio, Díaz, Carmen E., Pérez‐Hernández, Nury, González‐Coloma, Azucena, Joseph‐Nathan, Pedro
Format: Article
Language:English
Subjects:
Absolute configuration
Alcohols
Alkenes - chemistry
Artemisia absinthium
Artemisia absinthium - chemistry
Chemical equilibrium
Circular dichroism
Configurations
Constants
Coupling (molecular)
Density functional theory
Dichroism
Essential oils
Functional groups
monoterpenes
Monoterpenes - chemistry
Monoterpenoids
NMR
Nuclear magnetic resonance
Ocimene
ocimenes
Organic chemistry
Stereoisomerism
very‐high‐resolution nuclear magnetic resonance
vibrational circular dichroism
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Summary:The absolute configuration (AC) of the naturally occurring ocimenes (−)‐(3S,5Z)‐2,6‐dimethyl‐2,3‐epoxyocta‐5,7‐diene (1) and (−)‐(3S,5Z)‐2,6‐dimethylocta‐5,7‐dien‐2,3‐diol (2), isolated from the essential oils of domesticated specimens of Artemisia absinthium, followed by vibrational circular dichroism (VCD) studies of 1, as well as from the acetonide 3 and the monoacetate 4, both derived from 2, since secondary alcohols are not the best functional groups to be present during VCD studies in solution due to intermolecular associations. The AC follows from comparison of experimental and calculated VCD spectra that were obtained by Density Functional Theory computation at the B3LYP/DGDZVP level of theory. Careful nuclear magnetic resonance (NMR) measurements were compared with literature values, providing for the first time systematic 1H and 13C chemical shift data. Regarding homonuclear 1H coupling constants, after performing a few irradiation experiments that showed the presence of several small long‐range interactions, the complete set of coupling constants for 3, which is representative of the four studied molecules, was determined by iterations using the PERCH software. This procedure even allowed assigning the pro‐R and pro‐S methyl group signals of the two gem‐dimethyl groups present in 3.
ISSN:0899-0042
1520-636X
DOI:10.1002/chir.22741