Design, Synthesis, and Properties of Macrocyclic Receptors for Tetrahedral Substrates

In order to complex lipophilic molecules of tetrahedral shape, hosts made of two cyclotriveratrylene caps have been designed and named ”cryptophanes“. Cryptophanes can be synthesised in two different ways from vanillyl alcohol. In a first method, a C3‐cyclotriveratrylene of suitable structure is prepared and used as a template for intramolecular assemblage of the second cap. In a second method, much shorter, the two cyclotriveratrylene caps of the cryptophane are simultaneously built from appropriate vanillyl alcohol dimers. The complexation of halogenomethanes, aliphatic hydrocarbons, and polymethylammonium ions by certain D3‐cryptophanes has been studied. Neutral molecules such as chloroform and isobutane are comparatively strongly bound in organic solvents (1,1,2,2‐tetrachloroethane‐d2) and very strongly bound in water, whereas the tetramethylammonium cation shows an inverse behaviour. Choline and acetylcholine are bound in water at pH 5‐8. Some possible applications of these results are discussed.