Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

• Published in: Chirality (New York, N.Y.) Vol. 29; no. 11; pp. 716 - 725
• Main Authors: Julio, Luis F., Burgueño‐Tapia, Eleuterio, Díaz, Carmen E., Pérez‐Hernández, Nury, González‐Coloma, Azucena, Joseph‐Nathan, Pedro
• Format: Journal Article
• Language: English
• Published: HOBOKEN Wiley 01.11.2017; Wiley Subscription Services, Inc
• Subjects: Absolute configuration; Alcohols; Alkenes - chemistry; Artemisia absinthium; Artemisia absinthium - chemistry; Chemical equilibrium; Chemistry; Chemistry, Analytical; Chemistry, Medicinal; Chemistry, Organic; Circular dichroism; Configurations; Constants; Coupling (molecular); Density functional theory; Dichroism; Essential oils; Functional groups; Life Sciences & Biomedicine; monoterpenes; Monoterpenes - chemistry; Monoterpenoids; NMR; Nuclear magnetic resonance; Ocimene; ocimenes; Organic chemistry; Pharmacology & Pharmacy; Physical Sciences; Science & Technology; Stereoisomerism; very‐high‐resolution nuclear magnetic resonance; vibrational circular dichroism; ENCELIA-FARINOSA; H-1-NMR ASSIGNMENT; ESSENTIAL OILS; very-high-resolution nuclear magnetic resonance; VIBRATIONAL CIRCULAR-DICHROISM; vibrational circular dichroism; ocimenes; POPULATIONS; absolute configuration; DERIVATIVES; ANTIFEEDANT; monoterpenes
• ISSN: 0899-0042; 1520-636X
• DOI: 10.1002/chir.22741

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.