Polyethylene glycol , grafted onto polystyren

A variety of other substituents on the chain ends of polyethylene glycol) grafted onto polystyrene have been investigated for catalysis of the reaction of 1 -bromobutane and solid potassium phenoxide. The apparent activities of 2 % CL, 14% RS catalysts 56 (n = 4) wereZ = 2-(l,4-benzodioxanylmethyl) < tetrahydrofuran-2-yl < 2-pyri-dylmethyl < p-toluenesulfonyl < 8-quinolyl < 2-pyrrolidinon-l-yl < 2-methoxy-phenyl < 2-naphthyl179). 

PEG has been converted into a solid support by grafting functionalized polyethylene glycol chains onto polystyrene to form constructs such as TentaGel ... 

At present, two major families of supports are used for SPPS. Polystyrene, lightly cross-linked (e.g., 1%) with divinylbenzene, was used in most of Merrifield s seminal work and is still very popular for SPPS and solid-phase organic synthesis [1,22]. Polyethylene glycol (PEG) grafted onto polystyrene has found widespread application. The PEG chain can either be covalently attached to the polystyrene support (PEG-PS) [23-25] or ethylene oxide polymerized onto the polystyrene (Tentagel and ArgoGel) [26,27]. 

The solid support should be well solvated to facilitate reactions to take place involving the two phases. The original supports were based on polystyrene but have generally been superseded by polyamide resins, which have an advantage in that they have a similar polarity to the peptide backbone. More recently, resins based on polyethylene glycol (PEG) grafted onto low... 

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. 

However, despite the current popularity of CPG supports, the search for improved materials still continues, and recently two promising new supports based on polystyrene have been introduced. Bayer (25) has prepared a tentacle support (Fig. 5) that contains polyethylene glycol (PEG) chains grafted onto the surface of monodisperse polystyrene beads (PEG-PS). The hydrophilic PEG tentacles impart greatly improved swellability in the polar solvents required for oligonucleotide synthesis, and the uniform size and spherical shape of the mono-... 

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