Synthesis and characterization of d5-barbarin for use in barbarin-related research

Sucheta Kudrimoti, Jacob Machin, Adedamola S. Arojojoye, Samuel G. Awuah, Rodney Eisenberg, Clara Fenger, George Maylin, Andreas F. Lehner, Thomas Tobin

Research output: Contribution to journalArticlepeer-review


Based on structural similarities and equine administration experiments, Barbarin, 5-phenyl-2-oxazolidinethione from Brassicaceae plants, is a possible source of equine urinary identifications of aminorex, (R,S)-5-phenyl-4,5-dihydro-1,3-oxazol-2-amine, an amphetamine-related US Drug Enforcement Administration (DEA) controlled substance considered illegal in sport horses. We now report the synthesis and certification of d5-barbarin to facilitate research on the relationship between plant barbarin and such aminorex identifications. D5-barbarin synthesis commenced with production of d5-2-oxo-2-phenylacetaldehyde oxime (d5-oxime) from d5-acetophenone via butylnitrite in an ethoxide/ethanol solution. This d5-oxime was then reduced with lithium aluminum hydride (LiAlH4) to produce the corresponding d5-2-amino-1-phenylethan-1-ol (d5-phenylethanolamine). Final ring closure of the d5-phenylethanolamine was performed by the addition of carbon disulfide (CS2) with pyridine. The reaction product was purified by recrystallization and presented as a stable white crystalline powder. Proton NMR spectroscopy revealed a triplet at 5.88 ppm for one proton, a double doublet at 3.71 ppm for one proton, and double doublet at 4.11 ppm for one proton, confirming d5-barbarin as the product. Further characterization by high resolution mass spectrometry supports the successful synthesis of d5-barbarin. Purity of the recrystallized product was ascertained by High Performance Liquid Chromatography (HPLC) to be greater than 98%. Together, we have developed the synthesis and full characterization of d5-barbarin for use as an internal standard in barbarin-related and equine forensic research.

Original languageEnglish
Pages (from-to)42-46
Number of pages5
JournalDrug Testing and Analysis
Issue number1
StatePublished - Jan 2023

Bibliographical note

Funding Information:
This research was made possible by research support from The Equine Health and Welfare Alliance, Inc, Versailles, Kentucky, and the US Trotting Association, Columbus, OH. Further support came from the National Institute of Food and Agriculture, US Department of Agriculture, Hatch Program under project Accession Number 7001029. Other support includes research support from the National Horsemen's Benevolent and Protective Association and the Alabama, Arizona, Arkansas, Ontario, Canada; Charles Town, WV; Florida, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Nebraska, Ohio, Oklahoma, Oregon, Pennsylvania, Tampa Bay Downs, Florida, Texas, Washington State, and West Virginia Horsemen's Benevolent, and Protective Associations.

Publisher Copyright:
© 2022 The Authors. Drug Testing and Analysis published by John Wiley & Sons Ltd.


  • Barbarea vulgaris
  • aminorex
  • d-barbarin
  • equine forensic science
  • internal standard

ASJC Scopus subject areas

  • Analytical Chemistry
  • Environmental Chemistry
  • Pharmaceutical Science
  • Spectroscopy


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