Glycosides sugars

The maciocyclic lactone of all avermectins has an a-L-oleandtosyl-a-L-oleanchosyloxy substituent at carbon 13, which is a 2-deoxy sugar glycoside. 

The dialdehydes, such as VI and XI, produced by periodate oxidation of sugar glycosides or polymers, very probably do not exist in the aldehydo form,212-214 but in a hydrated212 and cyclized structure.213 214... 

Ethoxy-3,4-dihydro-6-methyl-2ff-pyran (179) has been used78 as the substrate for the synthesis of methyl 2,3,6-trideoxy-a-DL-enjthro-hex-2-enopyranoside (180). The synthesis consisted in hydroboration of the double bond, followed by oxidation, bromination at C-2, and elimination of HBr, to give 180. This compound was, in turn, converted into methyl DL-mycaminoside,7K DL-oleandroside,79 and other sugar glycosides (see Section III,2). 

Sugar Glycoside Original rate constant Equilibrium composition, % Solution time, hours... 

The protected amino sugar glycoside was treated with "acetobromorhamnose" under Koenigs—Knorr conditions and an excellent yield of the corresponding 3 0-a-L-rhamnosyl derivative... 

More difficult to construct, however, are the P-linkages in the case of 2-deoxy sugar glycosides. The B-C disaccharide subunit comprises such a problem. Starting... 

A treatment of the many types of replacement reaction which have received study by carbohydrate chemists would of necessity be superficial and thus defeat the present purpose. Instead, an attempt will be made to gather all information which sheds light on the mechanisms of a few types of reaction. The reactions of 0-acyl derivatives of sugars, glycosides, and glycosyl halides were chosen because of the central role these substances play in carbohydrate chemistry. 

Direct Conversion of Sugar Glycosides into Carbocycles... 

A cyclic acetal form of a sugar. Glycosides are stable to base, and they are nonreducing sugars. Glycosides are generally furanosides (five-membered) or pyranosides (six-membered), and they exist in anomeric a and [i forms, (p. 1119)... 

The following Tables record some physical properties of boronates of sugars, glycosides, C- and N-glycosyl compounds including nucleosides, alditols, and anhydro sugars. 

Bitter taste is elicited by structurally diverse compounds, including phenols, ions, amino acids and peptides, alkaloids, acylated sugars, glycosides, nitrogenous compounds, and thiocarbamates. Taste receptor cells are primarily associated with papillae on the tongue. The signal transduction mechanisms by which taste perception occurs are well not understood, but are the focus of intensive research as reviewed recently (6). 

The situation was clarified by the isolation of a, )8, and y isomers of D-glucose by Tanret in 1895. He showed that the a and y isomers mutarotate in opposite directions and, at equilibrium, each have the same rotation as the y3 form. The isomers were also found to have the same molecular weight. Tanret s three isomers of D-glucose were considered to be ring and free aldehyde forms by Lobry de Bruyn and Alberda van Ekenstein in 1895, von Lipp-mann in 1896, and Simon in 1901. Fischer in 1893, and von Lipp-mann pointed out that ring formation would produce a new asymmetric carbon atom, and thus the existence of isomeric sugars, glycosides, and acetates was clarified. 

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