Cyclodextrin analogue enzyme

We saw in Section 12.3.1 the use of the cyclodextrins as mimics for transacylases, a well-understood class of enzymes that perform the task of transferring an acyl group from one substrate to another (e.g. from an ester to water). Transacylase chemistry has also been addressed by Cram,5 who used chiral corands, such as 12.11, related to 3.106 bearing thiolate nucleophiles situated above and below the plane of the macrocycle. An acyclic analogue 12.12 was also prepared for comparison. The salient features of 12.11 are shown diagrammatically in Figure 12.4. 

Complexes with modified cyclodextrins were initially used as models of hydrolytic enzymes [20,181,197,198]. Then, Breslow and Kato studied such complexes in biomimetic oxidation and epoxidation. Reetz and some other researchers investigated them in hydroformylation. We examined cyclodextrin-based catalysts in hydroxylation and Wacker oxidation. Note that some of these studies demonstrated a substantial increase in the activity of the catalysts in comparison with their analogues prepared as ordinary mixtures, which was due to the cooperative substrate binding. 

AMP or ADP-analogues - NAD - or NADP -dependent enzymes cyclodextrines - different aromatic compounds... 

Other interesting systems involving cyclodextrin chemistry have been applied as enzyme models by I. Tabushi. They are specific allylation-oxida-tion of hydroquinone (188), cyclodextrin having an amino group attached to retinal as a rhodopsin model (189) and specific inclusion catalysis by j8-cyclodextrin in the one-step preparation of vitamin Kj and K2 analogues (190). 

As previously, this Chapter deals with specific tri- and higher oligosaccharides most references relate to their chemical or enzymic or chemoenzymic syntheses, and an increasing number of compounds which can be considered to be analogues of oligosaccharides have been reported. Likewise the cyclodextrins continue to attract increasing activity. Their chemistry is dealt with separately (Section 10). 

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