New Molecular Insights on Gabapentin

Neutral gabapentin has been vaporized by laser ablation and supersonically expanded to record its rotational spectrum using Fourier transform microwave spectroscopy. We report the detection of five stable conformers, which differ in the intramolecular interactions between the different functional groups (OH, C=O, and NH). Two configurations, axial and equatorial, are possible depending on the chair form of the cyclohexane ring, and both forms are detected, with the latter being predominant. The conformational landscape of gabapentin is compared with that of GABA, and significant differences are observed. One of the most meaningful results of such a comparison is that the relationship between the intramolecular interactions and the relative abundance within each type is reversed from GABA to gabapentin. It could explain the distinction in the mechanism of action of GABA and gabapentin, despite being structurally similar.