Other Glycosides

Despite the simple structure of a glucopyranoside linked to a colchicine or thio-colchicine moiety, subtilisin-catalyzed acylation of colchicoside and thiocolchico-side still represents the only example of regioselective esterification of alkaloid 

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Many other glycosides have been subjected to selective chlorination with sulfuryl chloride. Methyl /3-L-arabinopyranoside afforded methyl 4-chloro-4-deoxy-a-D-xylopyranoside 2,3-di(chlorosulfate) in 29% yield, whereas the a-L anomer gave357 methyl 3,4-dichloro-3,4-dideoxy-/3-i)-ribopyranoside 2-(chlorosulfate) (30%). Methyl /3-d-ribopyranoside was converted into methyl 3,4-dichloro-3,4-dideoxy-a-L-arabinopyranoside through the action of pyridine hydrochloride on its 2,3,4-tri(chlorosulfate).358 Methyl a-D-lyxopyranoside gave only the 2,3,4-tri(chlorosulfate),353 as would be expected from the disposition of its hydroxyl groups, similar to that in the rhamno- and manno-pyranosides. Methyl a-D-altropyranoside was transformed into the 6-chloro-6-deoxy 2,3,4-tri(chlorosulfate) derivative in 80% yield.353... 

Besides a chiral remote induction for glycosidation, other glycosidic sugar-fused lactones have been also directly used as saccharidic delivery synthons. 

Estrogenic Glycosides (Isoflavones, Coumestans) Coumarin Glycosides Goitrogenic Glycosides Other Glycosides... 

One result from the analysis of the MD simulation was the proposal of a new enzymic pathway for hydrolysis by lysozyme. We begin with a description of the alternative mechanism, and the basis on which it was proposed. The energetics of the individual GlcNAc units in the lysozyme cleft are then presented, followed by a graphical representation of the correlation between the atomic fluctuations of the substrate and those of the enzyme. Of particular interest is the fact that the binding interactions stabilize a bound state conformation for the two glycosides involved in hydrolysis that is optimum for catalysis by the alternative mechanism and which differs from the conformations of the other glycosides. These conformational features are described in the final two sections. 

Other glycosides which have been formed by direct substitution at 0-1 are tetrahydrop5uanyl (two diastereoisomers being obtained from each anomer) trityl and trimethylsilyl... 

The enzymatic glycosylation of natural products can be performed in principle by glycosidases, glycosyltransferases, and some other glycoside-processing enzymes -sometimes called transglycosidases. 

The interesting physiological effects of alkaloid fructosides [41] stimulated the preparation of other glycosides, such as galactosides, glucosides, A-glucosami-nides, and complex alkaloid glycosides. 

A series of other glycosides of ergot alkaloids was prepared by enzymatic transglycosylations using activated p-nitrophenylglycosides as donors [47]. 

Digoxin, the only cardiac glycoside used in the USA, is 65-80% absorbed after oral administration. Absorption of other glycosides varies from zero to nearly 100%. Once present in the blood, all cardiac glycosides are widely distributed to tissues, including the central nervous system. 

Several other glycosidation methods can also be considered as proceeding by remote activation. For example, treatment of 0-benzyl glycosyl trichloroacetimidates with BFj-EtjO [2 see also Chap. 11], or 0-benzyl pentenyl glycosides with NBS [19 see also Chap. 13] leads to activation at an atom not directly attached to the anomeric center. 

Tanner and Kandler296 suggested that, analogously to galactinol, other glycosides of myo-inositol may play important roles in the biosynthesis of various oligosaccharides. However, little is known in this respect. 

Like other glycosides, cyanogenic glycosides are cleaved to a carbohydrate and an alcohol on hydrolysis. 

The mechanism shown is one of two that are possible. The alternative mechanism would break the other glycoside bond to give glucose and the carbocation from the fructose unit. Both mechanisms undoubtedly occur simultaneously. The products, of course, are the same from both paths— namely, a mixture of the a and p forms of D-glucose and D-fructose. 

Several other glycosides of this class may be mentioned the tri-O-acetyl-/3-D-xylopyranoside of 3-methyluracil [3-methyl-2-(tri-0-acetyl-/3-D-xylopyranosyloxy)-3(4)-pyrimidone] (LXIII) which reduces Fehling (50) J. A. Snyder and K. P. Link, J. Am. Chem. Soc., 75, 1818 (1953). 

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