POEPOP

Polar polyoxyethylene-polyoxypropylene (POEPOP) resin, deriva-tized with a 4-hydroxymethyl phenoxy linker, was used as a solid support for lanthanide triflate-catalyzed Mukaiyama-type solid-phase aldol reactions.282 The use of an aqueous solvent was found to be crucial. The reactions on an N-terminal peptide aldehyde substrate proceeded in very high yields. 

As of this writing, there are presently only two examples of successful synthesis of glycopeptide libraries in the literature, and these have been generated using PEG-based resins (PEGA and POEPOP), thus enabling rapid solid phase screening of the library (see Sections 14.8 and 14.7.2). 

M. Renil, M. Meldal. POEPOP and POEPS Inert polyethylene glycol crosslinked polymeric supports for solid phase synthesis. Tetrahedron Lett. 1996, 37, 6185-6188. 

A range of PEG-based resins are available, including PEGA [24], POEPOP [25] and POEPS [26,27], that do not stand up to the harsh conditions employed during Friedel-Crafts reactions or acetolysis. To circumvent these drawbacks, the SPOCC that contains only primary ether bonds, secondary and quartemary carbon atoms was introduced. The synthesis of SPOCC resin is summarized in Scheme 20.3 [27]. 

The POEPOP resins are obtained by anionic polymerisation of monomers 3 and 4. The loading capacity can be controlled by the corresponding ratio of the monomers. Both POEPS and POEPOP resins show excellent swelling properties in solvents such as dichloromethane, DMF and water. 

Cross-linked polyoxyethylene-polystyrene (POEPS) and polyoxyethylene-polyoxypropylene(POEPOP)... 

Figure 2. The POEPS 7 and POEPOP 8 polyoxyethylene based resins.

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