Investigation of structure, vibrational and NMR spectra of oxycodone and naltrexone: A combined experimental and theoretical study

In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, 1H NMR and 13C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6–311++G** level of theory.Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm−1, for the 1H NMR peaks are 0.87 and 0.17 ppm and for those of 13C NMR are 5.6 and 5.3 ppm, respectively for naltrexone and oxycodone.

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► Synthesis and IR, NMR and X-ray crystallographic data for naltrexone and oxycodone.
► Optimization of their structures and obtaining calculated IR, Raman and NMR spectra.
► Comparison between experimental and computational molecular parameters.
► Comparison between observed and computed IR, 1H NMR and 13C NMR spectra.