SYNTHETIC SUPRAMOLECULAR CHEMISTRY

For many decades, the construction of organic compounds in the laboratory has relied on the remarkable abilities of the 20th century ‘alchemists’ — namely, synthetic organic chemists — to make and break covalent bonds. Careful selection of functional groups and reaction conditions, in conjunction with protection/deprotection protocols, constitute the ‘secrets’ and ‘tricks’ of their ‘art’ which is commensurate with ‘traditional’ organic synthesis [1,2]. Indeed, relying on multistep reaction sequences, the total syntheses of structurally intricate molecular compounds which are constructed entirely using covalent bonds — e.g., brevetoxin B [3], palytoxin [4], and the calichearubicins [5] — have been realized in recent times. These very elegant and successful syntheses have required enormous intellectual and hands-on effort by large teams of chemists over rather long periods of time — very often, several years. Moreover, these extremely complex, and often particularly beautiful, examples represent close to state-of-the-art as far as ‘traditional’ organic synthesis is concerned. Alas, they also highlight the difficulties and limitations associated with classical organic syntheses — specifically, that the multistep aspect of such syntheses can be extremely laborious and time-consuming. With the possible exception of some dendritic structures [6], it is becoming apparent that the construction of nanoscopic structures, of the same complexities as those found in biological systems, using these classical methods is out of the reach of even the most talented and optimistic of the 20th century chemists!