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Substituent carbohydrates

A. F. Hadfield, L. Hough, and A. C. Richardson, The synthesis of further analogues of trehalose containing fluoro and amino substituents, Carbohydr. Res., 80 (1980) 123-130. [Pg.65]

Osborn, H M I, Brome, V A, Harwood, L M, Suthers, W G, Regioselective C-3-O-acylation and 0-methylation of 4,6-0-benzylidene-(3-D-gluco- and galactopyranosides displaying a range of anomeric substituents, Carbohydr. Res., 332, 157-166, 2001. [Pg.106]

Y. Tezuka, K. Imai, M. Oshima, and K. -I. Ito, Carbon-13 NMR stmctural studies on cellulose ethers by means of their acylated derivatives. 6. Carbon-13 NMR structural study on an enteric pharmaceutical coating cellulose derivative having ether and ester substituents, Carbohydr. Res., 222 (1991) 255-259. [Pg.199]

Summary Silicones with substituents from natural sources can be synthesized following simple protocols. The modification can be either hydrophilic, oleophilic or both. As hydrophilic substituents carbohydrates and polyethers are used, as oleophilic substituents cholesterol and simple alkyl chains. The physicochemical properties, such as viscosity, reduction of surface tension and emulsification performance, of silicones with standard modifications and of silicone modifications with substituents fit>m natural sources are significantly different. [Pg.622]

Glasser, W. G., U. Becker, and J. G. Todd. 2000. Novel cellulose derivatives. VI. Preparation and diermal analysis of two novel cellulose esters with fluorine-containing substituents. Carbohydrate Polymers 42,393-400. [Pg.217]

It IS not possible to tell by inspection whether the a or p pyranose form of a par ticular carbohydrate predominates at equilibrium As just described the p pyranose form IS the major species present m an aqueous solution of d glucose whereas the a pyranose form predominates m a solution of d mannose (Problem 25 8) The relative abundance of a and p pyranose forms m solution depends on two factors The first is solvation of the anomeric hydroxyl group An equatorial OH is less crowded and better solvated by water than an axial one This effect stabilizes the p pyranose form m aqueous solution The other factor called the anomeric effect, involves an electronic interaction between the nng oxygen and the anomeric substituent and preferentially stabilizes the axial OH of the a pyranose form Because the two effects operate m different directions but are com parable m magnitude m aqueous solution the a pyranose form is more abundant for some carbohydrates and the p pyranose form for others... [Pg.1040]

A commonplace variation on the general pattern seen m carbohydrate structure is the replacement of one or more of the hydroxyl substituents by some other atom or group In deoxy sugars the hydroxyl group is replaced by hydrogen Two examples of deoxy sugars are 2 deoxy d nbose and l rhamnose... [Pg.1042]

Carbohydrates that have a carbon substituent attached to the mam chain are said to have a branched chain d Apiose and l vancosamme are representative branched chain carbohydrates... [Pg.1043]

Glycosides are a large and very important class of carbohydrate derivatives character ized by the replacement of the anomeric hydroxyl group by some other substituent Gly cosides are termed O glycosides N glycosides S glycosides and so on according to the atom attached to the anomeric carbon... [Pg.1043]

Anomeric effect (Section 25 8) The preference for an elec tronegative substituent especially a hydroxyl group to oc cupy an axial orientation when bonded to the anomeric carbon m the pyranose form of a carbohydrate Anti (Section 3 1) Term describing relative position of two substituents on adjacent atoms when the angle between their bonds is on the order of 180° Atoms X and Y m the structure shown are anti to each other... [Pg.1276]

Branched chain carbohydrate (Section 25 12) Carbohydrate in which the main carbon chain bears a carbon substituent in place of a hydrogen or hydroxyl group Bromohydrin (Section 6 17) A halohydnn in which the halo gen IS bromine (see halohydnn)... [Pg.1278]

Complications arising from other types of isomerism. Positional and geometrical isomerism, also described in Sec. 1.6, will be excluded for simplicity. In actual polymers these are not always so easily ignored. Polymerization of 1,2-disubstituted ethylenes. Since these introduce two different asymmetric carbons into the polymer backbone (second substituent Y), they have the potential to display ditacticity. Our attention to these is limited to the illustration of some terminology which is derived from carbohydrate nomenclature (structures [IX]-[XII]) ... [Pg.472]

As mentioned previously, cellulosic phases as well as amylosic phases have also been used extensively for enantiomeric separations more recently (89,90). Most of the work ia this area has been with various derivatives of the native carbohydrate. The enantioresolving abiUties of the derivatized cellulosic and amylosic phases are reported to be very dependent on the types of substituents on the aromatic moieties that are appended onto the native carbohydrate (91). Table 3 fists some of the cellulosic and amylosic derivatives that have been used. These columns are available through Chiral Technologies, Inc. and J. T. Baker, Inc. [Pg.66]

Modification of the Carbohydrate Ring Substituents. Replacement of hncomycin s 2-hydroxy group by methoxy or by hydrogen (74), or inversion of the configuration of the hydroxy group at C-4 or at C-2 destroys activity (75). [Pg.90]

An electronegative substituent adjacent to a ring oxygen atom also shows a preference for an axial orientation. This is known as the anomeric effect , and is particularly significant to the conformations of carbohydrates (B-71MI20100, B-83MI20100). [Pg.9]

Most parent structures consist essentially of an assembly of rings and/or chains, the degree of hydrogenation of which is defined (usually completely saturated or containing the maximum number of non-cumulative double bonds in cyclic portions), and having no attached functional substituents (the carbohydrates are a notable exception to this). The stereochemistry at all (or most) chiral centres is defined thus such parent structures are sometimes referred to as stereoparents . Some examples are shown (77)-(83). [Pg.28]

The incorporation of heteroatoms can result in stereoelectronic effects that have a pronounced effect on conformation and, ultimately, on reactivity. It is known from numerous examples in carbohydrate chemistry that pyranose sugars substituted with an electron-withdrawing group such as halogen or alkoxy at C-1 are often more stable when the substituent has an axial, rather than an equatorial, orientation. This tendency is not limited to carbohydrates but carries over to simpler ring systems such as 2-substituted tetrahydropyrans. The phenomenon is known as the anomeric ect, because it involves a substituent at the anomeric position in carbohydrate pyranose rings. Scheme 3.1 lists... [Pg.151]

Anomeric effect (Section 25.8) The preference for an electronegative substituent, especially a hydroxyl group, to occupy an axial orientation when bonded to the anomeric carbon in the pyranose form of a carbohydrate. [Pg.1276]

Vancomycin, ristocetin A and teicoplanin are produced as fermentation products of Streptomyces orientalis, Nocardia lurida and Actinoplanes teichomyceticus, respectively. All three of these related compounds consist of an aglycone basket made up of fused macrocyclic rings and pendant carbohydrate moieties (Fig. 2-1). The macrocycles contain both ether and peptide linkages. The aglycones of vancomycin and teicoplanin contain two chloro-substituted aromatic rings, while the analogous portion of ristocetin A contains no chloro substituents. [Pg.26]

For an alternative approach to naming carbohydrate residues as substituents see 2-Carb-31.2 [which would give the name (II )- or (lS)-L-arabinitol-l-C-yl for the above example, depending on the ligands at the branch point]. [Pg.101]

Note. In carbohydrate nomenclature, substitution at a heteroatom is normally indicated by citing the locant of the attached carbon atom, followed by a hyphen, and then the italicized heteroatom element symbol, e.g. 2-0-methyl, 5-N-acetyl. Substituents on the same kind of heteroatom are grouped (e.g. 2,3,4-tri-0-methy 1), and substituents of the same kind are cited in alphabetical order of heteroatoms (e.g. 5-N-acetyl-4,8,9-tri-0-acetyl). The alternative format with superscript numerical locants (e.g, N5,(/,(), ( -tetraacetyl), used in some other areas of natural product chemistry, is unusual in carbohydrate names. [Pg.117]

Where the new bridge is attached to oxygen (or a replacement heteroatom, e.g. nitrogen in an amino sugar) already indicated in the name of the unbridged carbohydrate, the bivalent substituent prefix denotes substitution at two heteroatoms as outlined in 2-Carb-24.1 and 2-Carb-25 [method (b)]. Heteroatoms not directly bonded to the carbohydrate chain are regarded as part of the bridge. [Pg.143]

Note 2. The use of prefixes ending in -ylidene for gem-bivalent substituent groups is traditional in the carbohydrate field, although no longer recommended in general organic nomenclature [14],... [Pg.144]

Synthetically produced or modified carbohydrate-protein conjugates are sometimes referred to as neoglycoproteins. The nomenclature for the carbohydrate-containing substituents in such structures is analogous to sequential oligosaccharide nomenclature (2-Carb-37.2)... [Pg.168]


See other pages where Substituent carbohydrates is mentioned: [Pg.535]    [Pg.418]    [Pg.90]    [Pg.91]    [Pg.117]    [Pg.230]    [Pg.1043]    [Pg.215]    [Pg.217]    [Pg.248]    [Pg.255]    [Pg.258]    [Pg.126]    [Pg.509]    [Pg.126]    [Pg.143]    [Pg.145]    [Pg.216]    [Pg.374]   
See also in sourсe #XX -- [ Pg.169 ]




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Carbohydrates substituent groups

Glycoproteins carbohydrate substituents

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