The nicotinic agonist cytisine: The role of the NH···N interaction

Producción CientíficaWe report a detailed structural study of cytisine, an alkaloid used to help with smoking cessation, looking forward to unveiling its role as a nicotinic agonist. High-resolution rotational spectroscopy has allowed us to characterize two different conformers exhibiting axial and equatorial arrangements of the piperidinic NH group. Unexpectedly, the axial form has been found as the predominant configuration, in contrast to that observed for related molecules, such as piperidine. This anomalous behavior has been justified in terms of an intramolecular NH···N hydrogen bond. Moreover, this interaction justifies the overstabilization of the axial conformer over the equatorial one and is crucial for the mechanism of action of cytisine over the nicotinic receptor, further rationalizing its behavior as a nicotinic agonist.Ministerio de Ciencia, Innovación y Universidades (project PID2019-111396GB-I00)Junta de Castilla y León (project VA244P20)European Research Council under the European Union’s Seventh Framework Programme (FP/2007- 2013)/ERC-2013-SyG (grant 610256 NANOCOSMOS