Proazaphosphatranes, also known as Verkade's superbases, are nonionic species, which exhibit catalytic properties for a wide range of reactions. The properly designed host molecule 3 and its protonated counterpart [3 center dot H]Cl-+(-) were synthesized to study how confinement can modify the stability and the reactivity of a Verkade's superbase. The results show that the encapsulation does not alter the strong basicity of the proazaphosphatrane, but dramatically decreases the rate of proton transfer.