Concave chemistry

It is fascinating to visualize the complex chemistry of new macro-cavities, which, by virtue of their almost infinite variability, are able to take up bigger convex molecules, organic cations and anions. There is hardly any doubt that the mostly convex-oriented organic chemistry of today ( convex chemistry ) will be complemented with an opposite chemistry of concave receptor molecules ( concave chemistry ). 

On the other hand, in concave reagents, the reactive group is located within the cavity [7]. The concave geometry of enzymes is translated into artificial reagents. The concave shape is retained but the reactive group in the active site is replaced by a standard reagent of organic chemistry. Furthermore the concave... 

When the concave reagents are compared to other reactions in Supramole-cular Chemistry a distinct difference must be noted Most other approaches try to bind the substrate in a host first. Then this complex reacts with a reagent which either is present in solution or attached to the host. For concave reagents and concave catalysts, however, there is no need for binding of the educt. In contrast, the protonation reactions can be interpreted as a reagent (H ) host complex. 

Calixarenes are a fascinating class of cyclooligomers having three-dimensional concave surface and relatively rigid structure. Their name derives just from their calyx-form (but various other suggestive forms can be properly constructed) able to act as a host for other molecules (e.g., fullerenes, ions and so on) and have assumed capital importance for their use in analytic chemistry (where are used as ion-selective electrode and electrochemical as well as optical sensors) [290], medicine and other fields. In medieine they assume partieular importance because ean be used in eancer treatments as non-toxic molecules to carry a toxic payload to the eaneer eells. 

The first two voliunes in this Templates in Chemistry series have focused on templates that control solution-phase reactions. Among the templates discussed in these two voliunes were convex and concave templates that mediate the formation of (macro)cyclic molecules and mechanically bound molecules with their intriguing intertwined topology. Also, three-dimensional templates that are used to imprint polymers and that organize compounds in the solid state for predestined reactions have been included in the earlier volumes. 

The field of dynamic combinatorial chemistry takes advantage of the template effect, and numerous macrocycles have been stabilized by a proper tanplate. Also for the construction of macrocycles for concave reagents, the template effect is very valuable. 

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