Investigation of the acid/base behaviour of the opium alkaloid thebaine in LC-ESI-MS mobile phase by NMR spectroscopy

As part of a research programme to establish an analytical method for the simultaneous detection of the five major opium alkaloids in poppy seeds by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) it was discovered that the inclusion of thebaine produced two peaks for the same compound. This was in contrast to the effective simultaneous detection, by LC-ESI-MS, of morphine, codeine, papaverine and noscapine. The presence of these two peaks for thebaine was investigated using nuclear magnetic resonance spectroscopy with deuterated solvents to emulate the mobile phase conditions experienced. It was found that the presence of 80%, or higher ratios of, water caused two epimeric forms of thebaine to be formed; this explained the presence of two peaks on the chromatogram. In contrast, when a lower water content was used with 1% acetic acid, one stable form of thebaine could be analysed and resulted in a single peak visible in the subsequent chromatography.

N-methylcodeinium iodide--crystal structure and spectroscopic elucidation

The correlation between the structure and the spectroscopic properties of N-methylcodeinium iodide (1) has been studied, using the methods of single crystal X-ray diffraction, IR-LD spectroscopy of oriented samples as a suspension in nematic liquid crystals, UV-vis spectroscopy and 1H and 13C NMR spectroscopy. HPLC tandem mass spectrometry (HPLC ESI MS/MS) and thermal methods were also employed. Quantum chemical calculations have been performed with a view to obtaining the electronic structure and vibrational properties of the title compound. Compound (1) crystallizes in the space group P2(1)2(1)2(1) and its cations and anions are joined by moderate intermolecular OH...I- interaction of length 3.442A. The codeine molecule exhibits the classical T-shape for opiates. A dihedral angle value of 86.4(5) degrees between the A/B/C and D/E planes is obtained. Rings A and B are effectively coplanar with an interplanar angle of 3.6(3) degrees.