Solid-phase polymer support

Polymer-Supported, Solid-Phase, and Automated Synthesis 219... 

SCHEME 54. Major concepts for the polymer-supported/solid-phase oligosaccharide synthesis glycosyl acceptor bound approach (A) and glycosyl donor bound approach (B). 

Most commercially available RO membranes fall into one of two categories asymmetric membranes containing one polymer, or thin-film composite membranes consisting of two or more polymer layers. Asymmetric RO membranes have a thin ( 100 nm) permselective skin layer supported on a more porous sublayer of the same polymer. The dense skin layer determines the fluxes and selectivities of these membranes whereas the porous sublayer serves only as a mechanical support for the skin layer and has little effect on the membrane separation properties. Asymmetric membranes are most commonly formed by a phase inversion (polymer precipitation) process (16). In this process, a polymer solution is precipitated into a polymer-rich solid phase that forms the membrane and a polymer-poor liquid phase that forms the membrane pores or void spaces. 

Howdle reported that a one-pot, simultaneous synthesis of block copolymers by enzymatic ROP and ATRP employing initiator 3, CL and MMA is possible in supercritical C02 (scC02) [17]. scC02 is a unique solvent because it combines gaslike and liquid-like properties most importantly in this case it plasticizes and liquefies polymers very effectively, allowing enhanced mass transport which contributes to more efficient polymerization, particularly important for a supported solid phase enzyme catalyst (see also Chapter 13) [28]. The authors also show that the CL acts as a scC02 co-solvent which was crucial to allow the radical polymerization to remain homogeneous and controlled [18]. The unique ability... 

The author s own interest in this area includes new functional polymers for solid phase synthesis [11-13], polymers with molecularly imprinted substrate selectivity [14], polymer-supported transition metal catalysts [15], novel polymers of potential interest for electrocatalysis [16], targeting of colloidal drug carriers [17, 18], molecular composites [19], and biocompatible surfaces [20]. These studies have led to, among other things, a uniquely versatile method of polymer synthesis based on the chemistry of activated acrylates, i.e. polymer synthesis via activated esters. Various aspects of polymers and copolymers of activated (meth)acrylates have also been investigated in this and several other laboratories. 

D. Solid-Phase and Polymer-Supported Solution-Phase Oligosaccharide Synthesis... 

The same 2-0-acetyl-protected mannosyl trichloroacetimidate was used in a polymer-supported solution-phase synthesis of a tetramannose moiety with polyethylene glycol monomethyl ether (MPEG) as polymer-support [196], The use of controlled-pore glass (CPG) as solid-phase support is under investigation in the synthesis of oligosaccharides [197] and glyconucleotide conjugates [198] with trichloroacetimidates as donors. 

E. C. Blossey and D. C. Neckers, Eds., Solid Phase Synthesis, Halsted, New York, 1975 P. Hodge and D. C. Sherrington, Eds., Polymer-Supported Reactions in Organic Synthesis, Wiley-Interscience, New York, 1980. A comprehensive review of polymeric protective groups by J. M. J. Frechet is included in this book. 

Polymer-supported esters are widely used in solid-phase peptide synthesis, and extensive information for this specialized protection is reported annually. Some activated esters that have been used as macrolide precursors and some that have been used in peptide synthesis are also described in this chapter the many activated esters that are used in peptide synthesis are discussed elsewhere. A useful... 

At the time of writing this book, SPOS is in an area of reladve infancy but has considerable potential. One of the main difficulties in SPOS lies in the lack of techniques available to monitor reacdons carried out on polymer supports. Unlike reacdons in solution phase, reactions on solid support cannot be monitored with relative ease and this has hindered the progress as well as the efficacy of solid supported synthesis of small non-peptidic molecules. Despite these difficulties, a large body of studies is available for SPOS. Recent reviews incorporate... 

C. Blackburn, Polymer supports for solid-phase organic synthesis, Biopolymers 47 311-351 1998. 

Synthetic organic polymers, which are used as polymeric supports for chromatography, as catalysts, as solid-phase supports for peptide and oligonucleotide synthesis, and for diagnosis, are based mainly on polystyrene, polystyrene-divinylbenzene, polyacrylamide, polymethacrylates, and polyvinyl alcohols. A conventional suspension of polymerization is usually used to produce these organic polymeric supports, especially in large-scale industrial production. 

Gels made in this way have virtually no usable porosity and are called Jordi solid bead packings. They can be used in the production of low surface area reverse phase packings for fast protein analysis and in the manufacture of hydrodynamic volume columns as well as solid supports for solid-phase syntheses reactions. An example of a hydrodynamic volume column separation is shown in Fig. 13.2 and its calibration plot is shown in Fig. 13.3. The major advantage of this type of column is its ability to resolve very high molecular weight polymer samples successfully. 

Polymer-supported esters are widely used in solid-phase peptide synthesis, and extensive information on this specialized protection is reported annually. Some activated esters that have been used as macrolide precursors and some that have been used in peptide synthesis are also described in this chapter the many activated esters that are used in peptide synthesis are discussed elsewhere. A useful list, with references, of many protected amino acids (e.g., -NH2, COOH, and side-chain-protected compounds) has been compiled/ Some general methods for the preparation of esters are provided at the beginning of this chapter conditions that are unique to a protective group are described with that group/ Some esters that have been used as protective groups are included in Reactivity Chart 6. 

Solid Phase Synthesis Versns Polymer-Supported Synthesis in Solution... 

Under certain condition, however, reactions are still preferably conducted in solution. This is the case e.g., for heterogeneous reactions and for conversions, which deliver complex product mixtures. In the latter case, further conversion of this mixture on the solid support is not desirable. In these instances, the combination of solution chemistry with polymer-assisted conversions can be an advantageous solution. Polymer-assisted synthesis in solution employs the polymer matrix either as a scavenger or for polymeric reagents. In both cases the virtues of solution phase and solid supported chemistry are ideally combined allowing for the preparation of pure products by filtration of the reactive resin. If several reactive polymers are used sequentially, multi-step syntheses can be conducted in a polymer-supported manner in solution as well. As a further advantage, many reactive polymers can be recycled for multiple use. 

Solid phase synthesis is a polymer-supported or solid-supported synthesis, i.e., stepwise construction of product molecules attached to an insoluble organic or inorganic polymer. 

A solid-phase Diels-Alder reaction that uses polymer-supported reagents has recently attracted considerable attention and its use is expanding rapidly. 

A polymer-supported silyl triflate and subsequent functionalization synthesis and solid-phase Diels-Alder reactions of silyloxydienes [25]... 

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