Ligands steric occlusion

Various strategies have been pursued in order to immobilise chiral epoxidation catalysts and these encompass covalent attachment to solid supports,[41] steric occlusion in nanosized cages of zeolites,[42 44] entrapment in a polydimethylsiloxane membrane145,461 and fluorous biphasic systems.1471 However, these approaches frequently require tedious ligand modifications and often lead to a marked decrease in both selectivity and activity of the transition metal catalyst. 

Fig. 9-4. Steric occlusion of the ligand, (a) If the matrix is heavily substituted with ligand, binding of the target protein to the ligand may be blocked, (b) At a lower concentration of ligand the target protein can freely interact with the ligand.

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