Solid supports cellulose

For the preparation of the triazine membranes, the entire solid support (cellulose or polypropylene membrane) was treated with a 5 m solution of the corresponding amine in l-methyl-2-pyrrolidinone (NMP) and a 1 m solution of cesium phenolate in dimethyl sulfoxide (2 p L of each at one spot) and subsequently heated in a domestic microwave oven for 3 min. After washing the support successively with... 

Cellulose was the first type of solid support introduced for SPPS [91 ] however, the scope of its use is limited by low loading capacity ( 0.1 mmol/g) and chemical stability. In spite of these drawbacks, microwave-assisted synthesis was successfully performed on cellulose membranes [92-94] and beads [95]. 

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

Various polymer matrices can be used as solid support into which pH indicator dye can be immobilized (cellulose, PVA, PVC). R. Makote and M.M. Collinson shows that also organically modified silicate films can be used for stable pH sensors37. 

A similar approach has been described by the same authors for the synthesis of related cyclic peptidomimetics [44]. A set often nucleophiles was employed for the substitution of the chlorine atom of the cyclic triazinyl-peptide bound to the cellulose membrane. By virtue of the aforementioned rate enhancement effects for nucleophilic substitution of the solid-supported monochlorotriazines, these reactions could be rapidly carried out by microwave heating. All products were obtained in high purity, enabling systematic modification of the molecular properties of the cyclic peptidomimetics. 

In a partition system the stationary phase is a liquid coated onto a solid support (p. 97). Silica gel, kieselguhr (diatomaceous earth) or cellulose powder are the most frequently used. Conditions closely resemble those of counter-current distribution so that in the absence of adsorption by the solid support, solutes move through the system at rates determined by their... 

Liquid ion-exchangers have been discussed in the section on solvent extraction (p. 65). They can be used in column form by coating them on to a solid support such as cellulose powder or Kel-F (polytrifluorochloroethylene). Tris-n-octylamine (TNOA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) behave as strong-base and strong-acid exchangers for anions and cations respectively. 

Sensors based on the above reaction scheme have been developed for Al3+, Zn2+, Cu2+, Ca2+, Pb2+, Hg2"1", K+, Li+, etc. A polycation, protamine sensor has also been developed using 2/7/-dichlorofluorescein octadecyl ester (DCFOE) doped in polymer membranes. However, most of these sensors are pH dependent due to the pH dependence of the cation complexation reactions. The cation ion indicators can be immobilized on any solid support, such as silica, cellulose, ion-exchange resin, porous glass, sol-gel, or entrapped in polymer membranes. 

For conventional or normal, in contrast with reversed-phase, LLPC, many materials have been used as the solid support for the stationary liquid. In addition to silica gel, which was the first and is still the most popular material, a variety of other adsorbents that adsorb the polar solvent such as cellulose powder, starch, alumina, and silicic acid have been used. The more recent practice of HPLC has greatly simplified the technique in providing column stability for repeated use and for treatment of large volumes. 

Cost sensitivity studies have shown that the successful commercialization of cellulase-based processes, such as the conversion of cellulose to fermentable sugars, is highly dependent on the cost of enzyme production (i). Because fungal -D-glucosidase (EC 3.2.1.21) is the most labile enzyme in this system under process conditions (2), and k to efficient saccharification of cellulose, this enzyme was targeted for application of stabilization technology, both through chemical modification and immobilization to solid supports. 

Fractional extraction242 (dissolution) may also be employed, as was demonstrated for a polyxylose, using batchwise extraction with aqueous ethanol.141 A more convenient procedure would involve adsorption of the polyglycose onto an inert, solid support (such as cellulose), followed by extraction using a procedure already described.243 The continuous nature of this process, the opportunity for solvent to reach all particles of the polymer, and the possibility of using gradient elution make this method attractive, particularly if the examination of a range of polymeric distributions is desired. 

Solid radioactive samples or those that are insoluble in either type of solvent may be quantified by collection onto small pieces of a solid support (filter paper or cellulose membrane) and added directly to the cocktail for counting. The efficiency of counting these samples depends on the support but is usually less than that of counting a homogeneous sample. 

A study of the influence of the nature of the solid support showed that silica, celite, cellulose or magnesium sulphate in combination with borohydride can also be used successfully in the microwave-assisted reduction of carbonyl compounds. The choice of the solid support has been reported to influence the chemoselectivity of the reduction of chalcone. Under optimised conditions the reduction of the alkene can be suppressed using borohydride on silica, whereas the use of cellulose as solid support seems to favour C=C reduction (Scheme 4.11 )27. 

Binding enzymes to solid supports can be achieved via covalent bonds, ionic interactions, or physical adsorption, although the last two options are prone to leaching. Enzymes are easily bound to several types of synthetic polymers, such as acrylic resins, as well as biopolymers, e.g., starch, cellulose [52], or chitosan [53,54]. Degussa s Eupergit resins, for example, are used as enzyme carriers in the production of semisynthetic antibiotics and chiral pharmaceuticals [55], Typically, these copolymers contain an acrylamide/methacrylate backbone, with epoxide side groups... 

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