Supramolecular substrate binding

The considerable interest in the design of container molecules [26, 27, 30], for their potential application as nano-scale chemical reactors has particularly received much attention [97]. In this sense, supramolecular catalysis allowing the chemical transformation of a substrate selectively entrapped within a molecular receptor, will behave as a chemical reactor [98]. One way to obtain a supramolecular catalysis, is to design a molecular receptor containing a lipophilic cavity allowing selective substrate binding, and specific sites for metal ion coordination [97, 99]. Attempts in this direction have... 

This chapter gives an overview of bio-inspired supramolecular catalytic systems that have been developed in our group since the early 1990s. Initially, attention was focused on the construction of relatively simple host-guest systems that were able to mimic certain aspects of enzymatic catalysis, e.g., substrate binding in a cavity and... 

In biochemical systems, enantiospecific receptor-substrate binding is of the utmost importance. As a result, there is a great deal of interest in the application of chiral supramolecular compounds as... 

Fig. 4 Expression/amplification of the optimal constituent from a triple dynamic library of potential receptor molecules through induced fit interaction with a substrate molecule (abarbiturate). In addition, there is a non-covalent/supramolecular dynamic process involving substrate binding and exchange...

Reaction control throngh complexation of substrate by supramolecular host is a relatively new idea compared to the conventional approaches that involve simple coUisional attack or coordination of snbstrate to metal. Multiple non-covalent interactions in supramolecular assembly bind and locate a site-specific substrate in the right position, orientation and conformation near the catalyst or active site, stabilize the high-energy transition state, and eventually make the reaction faster and more selective. Typical examples are found in enzymatic reactions, which proceed with high specificity and efficiency in aqueous solutions under mild conditions. These observations in natural systems have inspired... 

Lehn, J.-M. Meric, R. Vigneron, J.-P. Bkouche-Waks-man, L Pascard. C. Molecular recognition of anionic substrates. Binding of carboxylates by a macrobicyclic coreceptor and cryrtal stmcture of its supramolecular cryptate with the terephthalate ion. J. Chem. Soc., Chem. Commun. 1991. 2762-2771. 

These examples clearly demonstrate that well-defined geometries, with asymmetric environments around the active site, can be generated. Comfenation of the experimental information summarized here with the extensive knowledge currently available on synthetic receptors for selective substrate binding, opens intriguing possibilities for the design of sophisticated supramolecular catalysts. 

In the supramolecular species, [Nj cz (14)-6H ] (15), the ellipsoidal cryptand is built from two protonated tripodal subunits of the tren type N(CH2CH2NH2)3 located at each pole of the molecule and linked by three bridges. The two subunits are situated at a distance such that each may hold one of the two terminal nitrogens of the NJ ion, so that they cooperate in substrate binding. Bis-Tren-6H may be considered as a ditopic coreceptor for linear triatomic substrates of a size compatible with the size of the molecular cavity. 

Supramolecular Catalyst with Substrate Binding Sites... 

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