Polystyrene divinylbenzene copolymer resins phases

Polymer-supported triphenylphosphine ditriflate (37) has been prepared by treatment of polymer bound (polystyrene-2% divinylbenzene copolymer resin) triphenylphosphine oxide (36) with triflic anhydride in dichloromethane, the structure being confirmed by gel-phase 31P NMR [54, 55] (Scheme 7.12). This reagent is effective in various dehydration reactions such as ester (from primary and secondary alcohols) and amide formation in the presence of diisopropylethylamine as base, the polymer-supported triphenylphosphine oxide being recovered after the coupling reaction and reused. Interestingly, with amide formation, the reactive acyloxyphosphonium salt was preformed by addition of the carboxylic acid to 37 prior to addition of the corresponding amine. This order of addition ensured that the amine did not react competitively with 37 to form the unreactive polymer-sup-ported aminophosphonium triflate. 

SPE has been extensively used to analyse grape and wine volatiles, either in the form of resin cartridges or even in hand-prepared bed columns. The most used sorbents are Cis bonded phases, polystyrene/divinylbenzene copolymers and hydrophobic cross-linked polystyrene copolymer resins imder the commercial names Bond Elut C18, Discovery DSC-18, Strata C18, Lichrolut RP-18, Lichrolut EN, Chromabond easy. Strata SDB-L and Amberlite XAD-2, among others. 

Currently, the most widely used adsorbents in RPC are silica resins, containing a hydrophobic phase, usually octyl (C8), octyldecyl (C18), methyl (Cl), or phenyl groups. Additionally, new adsorbents based on organic materials such as methacrylate, polystyrene, and copolymers of styrene and divinylbenzene have been developed (Hearn, 1998). 

Different methods of solid-phase extraction (SPE) of wine volatiles were developed by using Amberlite XAD-2 polystyrenic resins (Gunata et al., 1985 Versini et al., 1988), reverse-phases Ci8 (Williams, 1982 Gianotti and Di Stefano, 1991 Di Stefano, 1991 Zulema et al., 2004 Ferreira et al., 2004), and more recently, highly cross-linked hydroxyl-ated polystyrenic phases (e.g., ENV+, Ferreira et al., 2004 Boido et al., 2003) and highly cross-linked ethylvinylbenzene-divinylbenzene copolymers (e.g., LiChrolut EN, Lopez et al., 2002 Ferreira et al., 2004 Genovese et al., 2005) stationary phases. 

Fmoc-aminomethyl-3,5-dimethoxyphen-oxy)valeric acid PEG, polyethylene glycol PEG-PS, polyethylene glycol-cross-linked polystyrene graft copolymer PS, copoly-(styrene-1% divinylbenzene) polymeric support , resin SPPS, solid-phase peptide synthesis tBu, tert.-butyl TEA, trifluoro-acetic acid TFE, trifluoroethanol THF, te-trahydrofuran TLC, thin-layer chromatography. Amino acid symbols denote the L-con-figuration. All solvent ratios and percentages are v/v unless stated otherwise. 

The most common formulation of ion-exchange resins is polystyrene cross-linked with divinylbenzene. The conventional styrene-divinylbenzene copolymer forms colorless transparent particles and consists of a homogeneous polymer phase. By changing the divinylbenzene content, one can modify the three dimesional networks of the copolymers. These resins are called gel-type copolymers. 

The organic and aqueous phases are prepared in separate tanks before transferring to the reaction ketde. In the manufacture of a styrenic copolymer, predeterrnined amounts of styrene (1) and divinylbenzene (2) are mixed together in the organic phase tank. Styrene is the principal constituent, and is usually about 90—95 wt % of the formulation. The other 5—10% is DVB. It is required to link chains of linear polystyrene together as polymerization proceeds. DVB is referred to as a cross-linker. Without it, functionalized polystyrene would be much too soluble to perform as an ion-exchange resin. Ethylene—methacrylate [97-90-5] and to a lesser degree trivinylbenzene [1322-23-2] are occasionally used as substitutes for DVB. 

Most synthetic methods for the generation of peptide libraries have been derived from various multiple parallel peptide synthesis techniques developed since 1984.bs-i l Consequently, the sohd supports used for hbrary synthesis are essentially the same as those used for multiple peptide synthesis. Standard divinylbenzene cross-linked polystyrene resins are typically used for hbraries that are cleaved from the resin and screened in solution.P Polyoxyethylene-grafted polystyrene resins,f l or acrylamide-polyoxyethylene copolymers, P on the other hand, are the sohd supports of choice for the synthesis of resin-bound peptide hbraries screened in sohd-phase binding assays.P Such resins are compatible with both organic solvents used for peptide synthesis, as well as aqueous buffers used in the bioassays. Various segmental supports previously employed for multiple peptide syntheses have also been utilized for the synthesis of peptide libraries, including polypropylene pins, PI cotton,t cellulose membrane,and glass shdes.P ... 

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