Organic synthesis on soluble polymeric supports

A recent review summarises the most important classes of soluble polymers, comprising supports derived from polyethylenglycol (PEG), polyvinylalcohol, polyethylene imine, polyacrylic acid, polypropylene oxide, cellulose, polyacrylamide to name the commonly used ones. 

While precipitation / crystallisation is easily automated, dialysis and gel permeation require more laborious workup procedures. In addition, precipitation / crystallisation seems to be less predictive and reproducible. Notably, it has been shown with soluble polystyrenes in the synthesis of e.g. oligosaccharides that the yields of purified polymer-bound products decreased considerably as the oligosaccharide chain grew due to increased solubility of the sugar-polymer conjugate in polar solvents.13 

An important feature of soluble polymer-bound libraries lies in the fact that biological screening can be performed in the standard format and that reactions can easily be monitored using H-NMR- and C-NMR spectroscopy. For the synthesis of biopolymers such as peptides CD spectroscopy was employed, e.g. for the synthesis of myoglobin 66-73.  

Similarly to insoluble supports, molecules are attached via a linker unit (see Chapter 1.7) to the support. Supports and linkers have to be chemically compatible with the reaction conditions employed for the library synthesis. Conversely, the final products have to be releasable without chemical modifications. Soluble supports have been successfully used for  

Hydrophilic polymeric supports are advantageous e.g. polyvinyl alcohol, cellulose, polyethyleneglycol. 

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