Adventures in molecular recognition. The ins and outs of templating

Two different approaches are described for the creation of supramolecular systems potentially capable of recognition and catalysis. Using the design approach, we have been able to accelerate and influence two different Diels-Alder reactions within the cavities of porphyrin dimers and trimers; this is templating from the outside inwards. The selection approach is a synthetic chemical attempt to capture some of the key evolutionary features of biological systems: dynamic combinatorial chemistry is used to create equilibrating mixtures of potential receptors, and then a template is used to select and amplify the desired system. Five potential reactions for such dynamic chemistry are discussed: base-catalyzed transes- terification, hydrazone exchange, disulfide exchange, alkene metathesis, and Pd-catalyzed allyl exchange, and preliminary templating results (inside outwards) are presented.