Oligosaccharide hosts cyclic

Table 14 1 /Is. Dn values of permethylated cyclic oligosaccharide hosts with amino acid ester hydrochloride guests...

Table 15 Chiral discrimination ability (t/Is-Dn values) of permethylated cyclic and acyclic oligosaccharide hosts toward amino acid 2-propyl ester salts by FAB-MS...

Host-guest inclusion complexes, 262—263 antibiotic hosts, 231—233 cahxarene hosts, 228—231 chiral crown ether hosts, 213—218 cyclic oligosaccharide hosts, 218—222 cyclodextrin host selectivities, 223/ host molecular size, 221 hnear ohgosaccharide hosts, 222—228 ir- TT stacking interactions, 217 proteic hosts, 231 Human 15-hpoxygenase, 52/... 

CDs are cyclic oligosaccharides comprised of a-l,4-linked glucopyr-anose units (37- 0). The following properties make CDs attractive components in organic chemistry and supramolecular catalysis/ enzyme mimics in particular (i) CDs are water soluble (ii) their hydrophobic cavity can host a variety of lipophilic guest molecules ... 

Among the best known and most versatile hosts are the various cydodextrins [1,2] of which a-, P- and y-cyclodextrins are the most available. These are cyclic oligosaccharides built up of six, seven, or eight glucopyranose units, respectively. These compounds can be prepared by enzymatic hydrolysis of starch. The undoubtedly most important member of the cyclodextrin family is P-cyclodextrin (P-CD) which has become a cheap and easily available chemical, suitable for large scale applications. Schemes... 

Cyclodextrins are cyclic oligosaccharides made up of several o-glucose units. Depending on the number of units, these doughnut-shaped molecules are able to host different sized molecules or the same molecule with different association... 

A similar chiral environment is given by inclusion to cyclodextrins (CDs), cyclic oligosaccharides (3). The outside of the host molecule is hydrophilic and the inside hydrophobic. The diameters of the cavities are approximately 6 (a), 7-8 (j3), and 9-10 A (7), respectively. Reduction of some prochiral ketone-j3-CD complexes with sodium boro-hydride in water gives the alcoholic products in modest ee (Scheme 2) (4). On the other hand, uncomplexed ketones are reduced with a crystalline CD complex of borane-pyridine complex dispersed in water to form the secondary alcohols in up to 90% ee, but in moderate chemical yields. Fair to excellent enantioselection has been achieved in gaseous hydrohalogenation or halogenation of a- or /3-CD complexes of crotonic or methacrylic acid. These reactions may seem attractive but currently require the use of stoichiometric amounts of the host CD molecules. 

Takai, Y., Okumura, Y., Tanaka, T., Sawada, M., Takahashi, S., Shiro, M., Kawamura, M., and Uchiyama, T., Binding characteristics of a new host family of cyclic oligosaccharides from inulin permethylated cycloinulohexoase and cycloinuloheptaose, J. Org. Chem., 59, 2967-2975, 1994. 

Cyclodextrin - A Naturally Occurring Cyclic Host Cyclodextrins are cyclic hosts made from oligosaccharides. They provide a hydrophobic microenvironment in an aqueous phase. 

The cyclic oligosaccharide cyclodextrins and the cychc ohgopeptide vali-nomycin were recognized as naturally occurring host molecules in he 1950s. Pedersen s discovery of crown ether in 1967 opened the door to research on... 

As mentioned above, some naturally occurring cyclic hosts that possess molecular recognition capabilities were known before crown ethers (the first artificial host molecules) were discovered. For example, the cyclic oligopeptide valinomycin and the cyclic oligosaccharide cyclodextrin were found to bind to specific guest molecules. The chemical modification of cyclodextrin was particularly well-researched, and artificially modified cyclodextrins became one of the most important compoimds used in host-guest chemistry. 

Hydrophobic interactions Cyclodextrins (sometimes abbreviated CDX) are cyclic oligosaccharides constructed from glucose units (Figure 11) [70], The most common are the hexa-, hepta- and octamer species, called respectively, a-, /J- and y-cyclodextrins. In 1948, Freudenberg and Cramer discovered that cyclodextrins could form inclusion compounds [71]. The formation of these host-guest complexes was studied systematically by Cramer and coworkers [72]. 

Cyclodextrins (CDs) are cyclic oligosaccharides which contain 6, 7, and 8 glucose units (a-, (3-, and y-cyclodextrins). The size of the fairly hydrophobic cavity of these compounds is defined by the number of glucose units (Fig. 5) [123]. Cyclodextrins have been extensively studied as models for host-guest complexes with a defined binding site, as models for catalytic systems, and have found application in chromatography [124-127]. Photophysical probe molecules... 

Hydrophilic P(EO-Z -MPC) block copolymers were synthesized and polymersome vesicles were prepared by complexing PEO segments with a-cyclodextrins. The latter are cyclic oligosaccharides containing a hydro-phobic internal cavity that acts as a host for various guest molecules.The polymersomes formed in aqueous medium without organic solvents and were found to be cytocompatible. DOX HCl has been successfully loaded into such polymersomes and efficiently delivered to cancer cells in vitro. 

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