Use of S-Mosher acid as a chiral solvating agent for enantiomeric analysis of some trans-4-(4-fluorophenyl)-3-substituted-1-methylpiperidines by means of NMR spectroscopy

Chiral NMR discrimination of the diastereoisomeric salts of the H3-antagonist 2-[3-(1H-imidazol-4-ylmethyl)piperidin-1-yl]-1H-benzimidazole

Diastereomeric salts with optically pure (S)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid (MTPA) were used to discriminate the enantiomers of the chiral H(3)-antagonist 2-[3-(1H-imidazol-4-ylmethyl)piperidin-1-yl]-1H-benzimidazole. Chemical-shift differences (Delta delta) in NMR spectra strongly depend on solvent and stoichiometric ratio. The better observable differentiation occurred for the proton at the 2-position of the imidazole ring.

Vibrational circular dichroism spectroscopy study of paroxetine and femoxetine precursors

The solution structures of (3R,4S)- and (3S,4R)- 4-(4-fluorophenyl)-3-hydroxylmethyl- 1-methylpiperidine, which are intermediates in the synthesis of the two pharmaceuticals paroxetine and femoxetine, were studied by vibrational circular dichroism (VCD) spectroscopy. In addition, six derivatives with different substituents attached to the C3 atom were prepared and their VCD and absorption spectra discussed with the aid of ab initio simulations. The VCD spectra were found to be sensitive to the geometry changes. In addition, a subtle variation caused by intermolecular aggregation was apparent in the spectra. The VCD technique can be applied for structural analysis of chiral pharmaceuticals in solutions.