Conformationally restricted GABA analogs: from rigid carbocycles to cage hydrocarbons.

GABA was discovered to play an important role as the major inhibitory neurotransmitter in the adult mammalian CNS 60 years ago. The conformational flexibility of GABA is important for its biological function, as it has been found to bind to different receptors with different conformations. In an effort to increase the lipophilicity and to reduce conformational flexibility of GABA itself, a polycyclic or cage hydrocarbon framework can be introduced into the 3D structure of GABA in order to better control the binding. This article explores the available synthetic methods, properties and activity of carbocyclic (cyclopropanes, cyclobutanes and cyclohexanes) and cage (adamantane and others) hydrocarbons - analogs of GABA with conformationally rigid carbon skeletons.