Carbohydrate glycosides

VIII. Miscellaneous Carbohydrates Glycosides, Vitamins, and Hydrazones. .. 90... 

Phospholipids also form complexes with proteins (e.g., vitellin in egg yoUc, animal and plant tissues, lipoproteins in blood serum, and milk), carbohydrates, glycosides, alkaloids, minerals, enzymes, cholesterol, and other substances. Lysophospholipids represent a special class of compounds resulting from the chemical or enzymatic hydrolysis of phospholipids. The role of phospholipases in normal and pathological conditions as well as in cell metabolism is of great biological significance (4). 

Celluloses Amines, amino acids, antibiotics, carbohydrates, glycosides, hydrocarbons, inorganic ions, nucleic acids, organic acids, peptides, urea derivatives, vitamins... 

Having brought home from Berlin Fischer s traditions and an overriding interest in natural products, particularly carbohydrate and glycoside chemistry, Zemplen established and ran his laboratory very much in the Fischer style, adding, however, his personal touches. The laboratories had tall ceilings and large windows (not unlike the Fischer... 

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... 

Sfrucfurally O glycosides are mixed acefals fhaf involve fhe anomeric posifion of furanose and pyranose forms of carbohydrates Recall fhe sequence of mfermediafes m acefal formalion (Secfion 17 8)... 

The preparalion of glycosides m Ihe laboratory is carried oul by simply allowing a carbohydrate to read wilh an alcohol m Ihe presence of an acid calalysl... 

A point to be emphasized about glycoside formation is that despite the presence of a number of other hydroxyl groups m the carbohydrate only the anomenc hydroxyl group IS replaced This is because a carbocation at the anomenc position is stabilized by the nng oxygen and is the only one capable of being formed under the reaction conditions... 

Disacchandes are carbohydrates that yield two monosaccharide molecules on hydroly SIS Structurally disaccharides are glycosides m which the alkoxy group attached to the anomeric carbon is derived from a second sugar molecule... 

Section 25 13 Glycosides are acetals compounds m which the anomenc hydroxyl group has been replaced by an alkoxy group Glycosides are easily prepared by allowing a carbohydrate and an alcohol to stand m the presence of an acid catalyst... 

The most important derivatives of pyrimidines and purines are nucleosides Nucleosides are N glycosides m which a pyrimidine or purine nitrogen is bonded to the anomeric carbon of a carbohydrate The nucleosides listed m Table 28 2 are the mam building blocks of nucleic acids In RNA the carbohydrate component is d ribofuranose m DNA It IS 2 deoxy d ribofuranose... 

Dowex 2-X8 1.2 0.75 Strongly basic (but less basic than Dowex 1 type) anion exchanger with S-DVB matrix for deionization of carbohydrates and separation of sugars, sugar alcohols, and glycosides. 

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. 

Sulfonate protective groups have been restricted largely to carbohydrates where they serve to protect the 2-OH with a nonparticipating group so that coupling gives predominantly 1,2-cw glycosides. 

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