Carbohydrates as ligands

A number of basic studies toward the application of carbohydrates as ligands for the [M(CO)3]+ entity have been described. Kliifers et al. demonstrated the ability of the hydroxy groups in a variety of carbohydrates to bind in different, pH and stoichiometry dependent ways to rhenium. A variety of complexes were structurally characterized [77]. Finally, two 1-thioglucose entities have been coupled to a central 4,4 -bipyridine ligand. These unique conjugates could be labeled at high dilution, exhibited perfect in vitro stability but were not yet subjected to biological studies [78]. 

Gyurcsik B, Nagy L (2000) Carbohydrates as ligands coordination equilibria and structure of... 

Gyurcsik B, Nagy L (2000) Carbohydrates as ligands coordination equilibria and structure of the metal complexes. Coord Chem Rev 203 81-149. doi 10.1016/80010-8545(99)00183-6... 

Among various amino alcohols used as ligands, derivatives of simple and easily available carbohydrates are only rarely reported and remain underestimated. In this context, a-hydroxy sulfonamides derived from D-glucosa-mine have been used by Bauer et al. for addition of ZnEt2 to aldehydes, providing the corresponding products in high enantioselectivities of up to 97% ee, as shown in Scheme 3.47. ... 

Carbohydrates not only act as ligands, but they can also provide scaffolds for molecular recognition processes. It is well known that cyclodextrins (CDs) are able to form an inclusion complex with specific guest molecules. In the last years, NMR experiments combined with other techniques have been used to highlight different recognition events. 

These initial reports showed that functional carbohydrate-mimetic peptides could be found. These peptides acted as ligands for several biologically important proteins, and had potential in the development of therapeutics. Subsequently, peptides that act as molecular mimics of carbohydrates in binding to a wide variety of different receptors have been identified [ 14-44] these are summarized in Table 1 and reviewed in [ 13]. Some of these peptides were able not only to bind to a particular receptor, but also to act as immunologically functional mimics and to induce an anti-carbohydrate immune re-... 

Fig. 2 A 1. 8-A resolution sigma-weighted (IFg-Fc) map of the octapeptide, contoured at la level. B Stereo view of the superimposed positions of the peptide [80] and carbohydrate [82] ligands. Atom types are the same as in Fig. 1. The ordered solvent (water) molecules (S) associated with the peptide complex are also shown. The solvent molecules S2, S9 and Si and the residue Rha C are shown to occupy a similar area of the site, the deep pocket of the combining site groove (see also Fig. 1). Reproduced from [80]. 2003 by The National Academy of Sciences of the USA...

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

Finally, carbohydrate ligands of enantioselective catalysts have been described for a limited number of reactions. Bis-phosphites of carbohydrates have been reported as ligands of efficient catalysts in enantioselective hydrogenations [182] and hydrocyanations [183], and a bifunctional dihydroglucal-based catalyst was recently found to effect asymmetric cyanosilylations of ketones [184]. Carbohydrate-derived titanocenes have been used in the enantioselective catalysis of reactions of diethyl zinc with carbonyl compounds [113]. Oxazolinones of amino sugars have been shown to be efficient catalysts in enantioselective palladium(0)-catalyzed allylation reactions of C-nucleophiles [185]. 

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