Soluble Supports in Solution-Phase Combinatorial Synthesis

5 SOLUBLE SUPPORTS IN SOLUTION-PHASE COMBINATORIAL SYNTHESIS 

Solid supports for SP synthesis are an important option for the synthesis of libraries of both discretes and pools. We have extensively reviewed their properties, but we have also highlighted some critical issues such as the different reaction kinetics in heterogeneous reactions due to accessibility of inner reaction sites, the difficulty of monitoring reactions on SP, and the need for suitable expertise and instrumentation. 

Since this first report, many other contributions have appeared, some of which have focused on the synthesis of libraries, whereas others describe the characterization of new p)ol5miers. The main classes of soluble supports will now be examined through examples, and their properties and use for specific applications will be reviewed. 

They are commercially available at reasonable cost in a wide range of average MWs and loadings. 

They have good solubility in most organic solvents and in water (see Fig. 8.47), but they are insoluble in n-hexane, diethyl ether, and cold ethanol, which induce their precipitation/crystallization, a property that can be used to advantage in purification protocols. 

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