Nitrile glycosides

Siegler, D.S. and Brinker, A.M. (1993) Characterisation of cyanogenic glycoside, cyanolipids, nitroglycosides, organic nitro compounds and nitrile glycosides from plants, in Methods of Plant Biochemistry, Alkaloids and Sulfur Compounds (eds P.M. Dey and J.B. Harbome) Academic Press, pp. 51—93. 

Mate contains both caffeine (0.4-2.4%) and theobromine (0.3-0.5%). Also found are triterpene saponins and the caffeic acid derivatives—chlorogenic acid, neochlorogenic acid, and cryptochlorogenic acid. Flavonoids in mate are rutin, isoquercetin, and kaemferol glycosides. A nitrile glycoside, menisdaurin, is also present, which is noncyanogenic. 

Another series of noncyanogenic nitrile glycosides, with structural similarities to intermediates in cyanogenic glycoside biosynthesis are found in members of the Aquifoliaceae, Boraginaceae, Crassulaceae, Menispermaceae, Fabaceae, Ranunculaceae, and Simmondsiaceae (Fig. 16.19) (Seigler, 1991). 

The removal of the carbohydrate auxiliary group and the hydrolysis of the amino nitriles is achieved by acidolytic cleavage of the hemiaminal /V-glycosidic bond and the concomitant acid-catalyzed solvolysis of the nitrile using either hydrogen chloride in formic acid or hydrogen bromide in acetic acid56 57. 

Formyl C-glycosides, prepared in three steps via the thiazole-based formy-lation of sugar lactones are readily condensed with hydroxylamine to give the corresponding oximes. The latter are the precursors of glycosyl nitrile oxides via the N-bromosuccinimide method (41). 

The synthesis of multivalent neoglycoconjugates by 1,3-dipolar cycloaddition of nitrile oxides and alkynes has been reported (493). The nitrile oxides have been generated in situ in the presence of alkynyl derivatives, allowing the access to homo and hetero multivalent systems containig O- and C-linked glycosides and isoxazole bridges. 

Biocatalytic hydrolysis or transesterification of esters is one of the most widely used enzyme-catalyzed reactions. In addition to the kinetic resolution of common esters or amides, attention is also directed toward the reactions of other functional groups such as nitriles, epoxides, and glycosides. It is easy to run these reactions without the need for cofactors, and the commercial availability of many enzymes makes this area quite popular in the laboratory. 

R. R. Schmidt, M. Behrendt, and A. Toepfer, Nitriles as solvents in glycosylation reactions Highly selective (3-glycoside synthesis, Synleti p. 694 (1990). 

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