Carbohydrates functional groups

Most of the key transformations described here involve carbon-carbon bond formation. Carbohydrate functional group manipulations are a long-standing research area in carbohydrate chemistry often reviewed in specialized books and series. We hope to provide the reader with a set of different chemical modifications of carbohydrate ring systems or acyclic carbohydrates available to devise new synthetic routes to biologically relevant targets. 

Some on-carbohydrate functional groups that may be part of the structure of a polysaccharide... 

The graphic interface is a multitasking environment that works well. The protein and carbohydrate builders are particularly convenient to use. The small-molecule builder has a selection of common organic functional groups as well as individual atoms for organics and common heteroatoms. There are a... 

Aldoses incorporate two functional groups C=0 and OH which are capable of react mg with each other We saw m Section 17 8 that nucleophilic addition of an alcohol function to a carbonyl group gives a hemiacetal When the hydroxyl and carbonyl groups are part of the same molecule a cyclic hemiacetal results as illustrated m Figure 25 3 Cyclic hemiacetal formation is most common when the ring that results is five or SIX membered Five membered cyclic hemiacetals of carbohydrates are called furanose forms SIX membered ones are called pyranose forms The nng carbon that is derived... 

Although carbohydrates exist almost entirely as cyclic hemiacetals m aqueous solution they are m rapid equilibrium with their open chain forms and most of the reagents that react with simple aldehydes and ketones react m an analogous way with the carbonyl functional groups of carbohydrates... 

Carbohydrates are marvelous molecules In most of them every carbon bears a functional group and the nature of the functional groups changes as the molecule mterconverts between open chain and cyclic hemiacetal forms Any approach to understanding carbohydrates must begin with structure... 

C1O3/ACOH, 25°, 50% yield, [- ROCOPh (- ROH + PhC02H)]. This method was used to remove benzyl ethers from carbohydrates that contain functional groups sensitive to catalytic hydiogenation or dissolving metals. Esters are stable, but glycosides or acetals are cleaved. 

We ll see numerous instances in future chapters where the chemistry of a given functional group is strongly affected by being in a ring rather than an open chain. Because cyclic molecules are so commonly encountered in all classes of bioniolecules, including proteins, lipids, carbohydrates, and nucleic acids, it s important that the effects of their cyclic structures be understood. 

Aldose (Section 25.1) A carbohydrate with an aldehyde functional group. 

Comprehensive Organic Chemistry , Pergamon, Elmsford, NY, 1979, is a six-volume treatise on the synthesis and reactions of organic compounds. The first three volumes cover the various functional groups, vol. 4, heterocyclic compounds, and vol. 5, biological compounds such as proteins, carbohydrates, and lipids. Probably the most useful volume is vol. 6, which contains formula, subject, and author indexes, as well as indexes of reactions and... 

Because they are readily available from natural sources in enantiomerically pure form, carbohydrates are very useful starting materials for the synthesis of other enantiomerically pure substances. However, the high number of similar functional groups present in the carbohydrates requires versatile techniques for protection and deprotection. Show how appropriate manipulation of protecting groups and other selective reactions could be employed to effect the following transformations. 

Synthetic efficiency. In many organic syntheses, it may be possible to eliminate the need for the protection and deprotection of functional groups, and save many synthetic steps. Water-soluble substrates can be used directly. This will be especially useful in carbohydrate and protein chemistry. 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

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