Solid crosslinked polystyrene resin

For quantitative analysis of solid supported thiol residues on free macroporous or PEG grafts, Ellman s reagent has been used [5,5 -dithio-hfr-(2-nitrobenzoic acid]. However only qualitative information can be gained using lightly crosslinked polystyrene resins [Badyal et al. Tetrahedron Lett 42 8531 2007]. 

Likewise, in the preparation of many ion-exchange resins, suitable functional groups are introduced by secondary reactions of macromolecular substances (that are generally crosslinked see Sect. 5.2). In this context the utilization of crosslinked polystyrene resins or poly(acrylamide) gel in the solid-phase synthesis of polypeptides (Merrifield technique) or even oligonucleotides should be mentioned. After complete preparation of the desired products they are cleaved from the crosslinked substrate and can be isolated. 

Scheme 7.13. Solid-phase synthesis with Pam linker on polystyrene resin. Note that polystyrene resin is crosslinked by incorporating a small quantity of divinylbenzene.

Early work on the application of NMR conventional techniques to the study of solvent swollen crosslinked polymers was reported by Stenlicht and co-workers [92] and Schaefer [93]. The first detailed work on the chlorome-thylated polystyrene resins used in solid phase synthesis appears to be by Manatt and co-workers [94]. They employed a 0.095% crosslinked species supplied by the Dow Chemical Co. and chloromethylated this to varying degrees. noise decoupled C NMR spectra were recorded in the usual... 

G. (1985) Preparation and use of an Aminoethyl Polyethylene Ctycol-crosslinked Polystyrene Graft Resin Support for solid-phase peptide synthesis. In Peptides structure and function, Proceedings of the Ninth American Peptide Symposium, (eds. L. M. Deber, V.J. Hruby, K.D. Doppler), Piene Chemical Co., Rockford, IL, pp. 257-60. 

Polystyrene resin, frequently used resin material for solid-phase peptide synthesis (SPPS). The polymeric support for SPPS must be chemically inert, mechanically stable, completely insoluble in the solvents used, and easily separated by filtration. For many applications a copolymer of polystyrene with 1% of divinyl benzene as crosslinker is used. The dry resin beads are able to swell up to the five-or sixfold volume in the different organic solvents mainly used for peptide synthesis (e.g., dichloromethane or dimethylfor-mamide). For SPPS the resin material must be chemically functionalized in order to allow for attachment of a handle/liker (e.g. Wang resin), or the first amino acid (—> Merrifield resin). Hydrophilic tentacle polymers gels (TentaGel) are obtained by grafting polyethylene glycol (PEG) chains with an arbitrary degree of polymerization onto porous polystyrene beads. 

Fig. 5. Solid-phase supports made of synthetic resins. Figs 1 and 2 The nucleoside linkages used on the early polystyrene popcorn supports (3,4). Fig. 3. The nucleoside linkage used on a polyamide based resin (5). Fig. 4 The structure of a polyamide/silica gel composite developed for continuous-flow synthesis (8) Fig. 5. The structure of a PEG-polystyrene grafted copolymer, tentacle support (25). The mean mol wt of die PEG side chain is 3000 daltons. Fig 6 The nucleoside linkage used on the recently introduced highly crosslinked polystyrene support (27).

The leading solid phases are the 2-chlorotrityl chloride resins. Professor K. Barlos (University of Patras, Greece) has made the single most important contribntion to the development of these resins. They consist of a polystyrene-base resin crosslinked with a small amonnt of divinylbenzene and functionalized with 2-chlorotritiyl chloride. 

Ag and Co functionalized adsorbents for the PPhs adsorption. These transition-metal functionalized adsorbents were prepared by immobilizing Ag and Co onto a solid carrier, for which Amberlyst IS has been selected. Amberlyst 15, a macroreticular polystyrene - crosslinked by divinylbenzene - sulfonated cation exchange resin, has been selected as carrier because of its large pore diameter of approximately 100 [nm]. These macropores ensure the accessibility for the relatively large PPh3 ligands. 

Besides the classical polymer introduced by Merrifield (1%-crosslinked chloromethylated polystyrene), a broad variety of polymeric supports is available for SPPS and some of the most popular resins are summarized in Table 1. The chemical structures of some selected resins are presented in Figure 1 and electron micrographs of several examples are displayed in Figure 2. In addition to the solid supports listed in Table 1, there are several other carriers used in peptide synthesis such as the gel-type and macroporous poly(meth-acrylates), coated surfaces like polystyrene films on polyethylene (PEt) sheets, polystyrene-coated polyethylene or polytetrafluoroethylene, and modified glass surfaces. (For recent reviews on polymeric carriers see refs . )... 

Solid-state CP and single pulse excitation (SPE) MAS NMR analysis of crosslinked particulate polystyrene-based resins... 

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