Poly carbohydrate derivatives

The periodate oxidation of carbohydrates, an important analytical technique, has been reviewed earlier in this Series.73 The dialdehydes obtained on periodate oxidation of polysaccharides have also been discussed.74 The requisite for the degradations to be discussed here is that part of the sugar residues in a polysaccharide are not oxidized by periodate and can be obtained separated from the oxidized residues as mono-, oligo-, or poly-saccharide derivatives after some chemical treatment. Characterization of these products may then give significant structural information. 

Only syntheses which involve the formation of new glycosidic linkages will be considered in this article. This restriction excludes many interesting examples of copolymerization in which only one of the monomers is a carbohydrate (or carbohydrate derivative), the polymerization of carbohydrate derivatives which contain a polymerizable group4 (such as acrylate), and the polymerization of sugar lactones.1 Many of these topics have already been discussed in reviews.1-8 Also outside the scope of this article is the chemical modification of naturally occurring polysaccharides thus, we have excluded the industrially important process of dextrini-zation,10 except as it may pertain to acid condensation processes. The radiation-catalyzed polymerization and modification of carbohydrate poly-... 

When secondary sulfonates are treated with LAH, competing reactions frequently occur. For poly-oxygenated, carbohydrate-derived substrates, complexation of the reagent, inductive deactivation and... 

Glycodendrimers can be synthesized by both convergent and divergent strategies. Ideally, they can be simply prepared by conjugation of active carbohydrate derivatives onto preformed dendrimers (Scheme 11). Given the commercial availability of poly(amidoamine) (PAMAM, 56) and poly(propyleneimine) (Dab, 57) dendrimers, these amine-ending dendrimers are the most heavily exploited. 

The use of polymers for the immobilization of enzymes and other bio-logically-active molecules has been discussed. The advantages of polymeric support materials and rules for their selection according to the type of use have been discussed. A review of various types of polymers which can serve as support matrices has been given. They are, e.g., polymeric carbohydrate derivatives, poly(allyl carbonate) and poly(allyl alcohol), polymers of acrylamidosalicylic acids, polyacrylamide derivatives, etc. Some examples of the use of immobilized enzymes and other biologically-active molecules were mentioned. 

Water-soluble polymeric compounds. These can be natural or modified natural products such as gelatine, starch, or carbohydrate derivatives such as methyl cellulose, hydroxyalkyl cellulose, or salts of carboxymethyl cellulose. Synthetic polymers such as poly(vinyl alcohol), partially hydrolyzed poly(vinyl acetate), sodium salts of poly(acrylic acids), methacrylic acids, and copolymers thereof are widely used in quantities between 0.1 and 1% related to the aqueous phase. 

The incorporation of two nonidentical chiral residues, each supporting C2 symmetry, into a mactocyclic poly ether affords a chiral crown compound with C2 symmetry provided its structure is constitutionally symmetrical. Thus, base-promoted reaction of the half-crown diol prepared from (5)-birraphthol with the half-crown ditosylate d-72 synthesized tom diacetone-manrritol affords (144) the 20-crown-6 derivative (S)-d-113 with C2 symmetry. When d-72 is condensed in like fashion with (/ 5)-binaphthol, then the diastereoisomeric 20-crown-6 derivative (/ )-d-114 can be separated chromatogiaphically tom (S)-d-113. In this matmer, (/ 5)-binaphthol is resolved by the carbohydrate unit during the synthesis. 

New polymeric solid supports have been devised, which include macroporous styrene-divinylbenzene containing large fixed pores, porous glass beads, insoluble carbohydrate polymers, poly(ethylene oxide), cross-linked derivatives of polyacrylamide resins, and graft copolymers of polystyrene and poly(ethylene oxide). The last two have been the most effective and widely used and have competed well with the original copoly(styrene-divi-nylbenzene) beads. 

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