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- Title
Resolution of isoborneol and its isomers by GC/MS to identify "synthetic" and "semi‐synthetic" borneol products.
- Authors
Yang, Ming‐Yeh; Khine, Aye Aye; Liu, Jen‐Wei; Cheng, Hui‐Chen; Hu, Anren; Chen, Hao‐Ping; Shih, Tzenge‐Lien
- Abstract
Borneol is a plant terpene commonly used in traditional Chinese medicine. Optically pure (+)‐borneol and (−)‐borneol can be obtained by extraction from the plants Dipterocarpaceae and Blumea balsamifera, respectively. "Synthetic borneol" is obtained from the reduction of (±)‐camphor to lead to four different stereoisomers: (+)‐isoborneol, (−)‐isoborneol, (+)‐borneol, and (−)‐borneol. In contrast, "semi‐synthetic borneol" is produced from the reduction of natural camphor, (+)‐camphor, to afford two isomers: (−)‐isoborneol and (+)‐borneol. We established a convenient method to identify them by treating the four stereoisomers with two chiral reagents, (R)‐(+)‐α‐methoxy‐α‐trifluoromethylphenylacetyl chloride ((R)‐(+)‐MTPA‐Cl) and (1S)‐(−)‐ camphanic chloride. The resulting derivatives from the above mentioned method were analyzed by gas chromatography. The enantiomers of (+)‐ and (−)‐isoborneol were successfully separated from (+)‐ and (−)‐borneol isomers in this study to make this a useful method in the identification of "synthetic" and "semi‐synthetic" borneols. Furthermore, we also examined five different commercial borneols. During this course, a novel and unprecedented partial epimerization from isoborneol‐camphanic ester to borneol‐camphanic ester was observed. However, this phenomenon did not occur in isoborneol‐MTPA esters epimerization to borneol‐MTPA case under the same conditions. The DFT calculation of activation energies for both reactions was in a good agreement with the results obtained from GC analysis. "Synthetic borneol" and "semi‐synthetic borneol" are obtained from the reduction of (±)‐camphor and (+)‐camphor, resulting in four and two stereoisomers, respectively. A convenient GC/MS method to identify them was established in this report. Commercial products are also examined by this method.
- Subjects
BORNEOLS; CHINESE medicine; TRADITIONAL medicine; PLANT extracts; STEREOISOMERS; CAMPHOR
- Publication
Chirality, 2018, Vol 30, Issue 11, p1233
- ISSN
0899-0042
- Publication type
Article
- DOI
10.1002/chir.23017