Functionalized carbohydrates

Nevertheless, the isolation of these metabolites was interesting in two respects. First, the structure of the thiazole glycol stimulated the research of functionalized carbohydrate chains as precursors of thiazole. Second, the thiazolecar-boxylic acid 40 can be secreted by derepressed cells in relatively high amounts, 0.24 nmol per mg of dried cells, which is nearly half the amount of synthesized thiamine. The presence of this free thiazolic derivative in the cells contrasts with... 

In a related study, Turnbull and coworkers described the attachment of carbohydrates to amino-derivatized glass slides. They found a significant rate enhancement when performing this step under microwave irradiation as compared to classical heating [47]. This method should be an efficient aid for the construction of functional carbohydrate array systems. 

The epoxidation of nonfunctionalized alkenes may also be effected by chiral dioxiranes. These species, formed in situ using the appropriate ketone and potassium caroate (Oxone), can be formed from C-2 symmetric chiral ketones (29)[93], functionalized carbohydrates (30)[94] or alkaloid derivatives (31)[95]. One example from the laboratories of Shi and co-workers is given in Scheme 19. 

Physioiogicai There is an extensive literature that deals with the effects ginseng on CNS function, but effects are also seen in neuroendocrine function, carbohydrate and lipid metabolism, the immune system, and cardiovascular function (Gillis 1997). Ginsenosides induce a decrease in heart rate and have biphasic effects on blood pressure, with decreases preceded by a slight increase (Kaku et al. 1975). Ginsenoside Rgl had the most potent effects on blood pressure. Little or no effect is observed on respiration. 

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-... 

A useful application of the chemistry shown in Scheme 83 is the synthesis of branched-chain functionalized carbohydrates. For this purpose two epoxides 261 and 262 derived from D-glucose and 263 derived from D-fructose were prepared following reported methodologies, and were submitted to a DTBB-catalyzed lithiation as described above in Scheme 83. The expected intermediates 264-266 and final products 267-269 were prepared in a regio- and stereoselective manner in 15- 95% yield" Also here, the use of a prochiral electrophile gave equimolecular amounts of both diastereomers. 

Other glycopolymers carrying a sialyl Lewisx mimic were obtained by copolymerization of functionalized carbohydrate monomers with acrylamide for... 

Grafting of Allyl-Functionalized Carbohydrates with Protective groups by Hydrosilylation... 

Parsons WB (1961a) Studiesontheuseofnicotinicacidinhypercholesterolemia changes in hepatic function, carbohydrate tolerance and uric acid metabolism. Archives of Internal Medicine 107, 653-67. 

Fabrication of a glycan array involves several interrelated factors choosing a solid support format, choosing a method to attach glycans to that solid support, and obtaining appropriately functionalized carbohydrates for immobilization. 

Specific optical rotation, circular dichroism (CD), and the newly developed exciton chirality method [96] for functionalized carbohydrates bearing specific chromophores are particularly... 

Feizi T, Lawson AM, Chai W (2003) Neogly-coUpids identification of functional carbohydrate epitopes. In Wong C-H (ed) Carbohydrate-based Drug Discovery from the Laboratory to the CUn-ic. Wiley-VCH, Weinheim, chap 27, p 747... 

A rapidly developing class of functional carbohydrates are the prebiotics (O Chap. 5.3). Currently these selectively stimulate health-positive bacteria in the colon [256]. There are, however, possibilities to enhance their functionality. One such functional enhancement would be persistence of the prebiotic fermentation to the distal colon [263]. One way to approach this is to produce oligosaccharide mixtures with controlled molecular weight distributions. 

The tests that are routinely performed provide information concerning hepatocellular and biliary integrity and function, renal function, carbohydrate, protein and lipid metabolism, and mineral and electrolyte balance. Modern analytical techniques require only small sample volumes to make accurate determinations, allowing in-life evaluations of effects in rats and larger species at multiple times during the course of a study without compromising animal health. 

A further example of the cyclization of a highly functionalized carbohydrate derivative is given by the preparation of polyhydroxylated cyclopentanes from halogenated carbohydrates19. Treatment of the olefinic halides with tributyltin hydride affords two isomeric products. 

Figure 1 An injury can be defined as a discontinuity in tissue integrity and healing as a process of restoring that integrity. Skin has two main forms of healing with very different outcomes in terms of appearance and function. Carbohydrates are used in a number of roles to enhance healing.

The relatively easy preparation of tailored azide- and alkyne-functionalized carbohydrate derivatives, as well as the efficiency of the click reaction with complementary counterparts, determine that this reaction could be considered at the present as a valuable synthetic tool. In spite of the fact that the reported examples summarized here reveal the potential of this cycloaddition reaction, their applications in the carbohydrate field are just beginning to be explored. A fruitful future can be anticipated, limited only by the level of creativity of the research community. 

The carrier can be organic (polylactic acid [PLA] - and poly(lactic-co-glycolic acid) [PLOA]" ) or inorganic (chitosan - poly(N-isopropylacrylamide) " hydrogelator silk protein pectin " hydrazide- and aldehyde-functionalized carbohydrates dextran hydroxyethyl methacrylate and silica ). 

In another example, Postel and co-workers used functionalized carbohydrates to produce P-substituted polyoxygenated furans. Treatment of functionalized benzylidene precursors with TMS-N3 in the presence of dibutyltin oxide gave the corresponding furan in 10% yield. The authors used a computational approach to rationalize furan formation via a series of cascade fragmentation reactions obtained during 1,5-C-H insertion from alkylidenecarbenes. 

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