Synthesis of glycosides

The compounds to be discussed in this category are structurally unrelated, except that they contain a monosaccharide residue or oligosaccharide residue attached to an aglycon which may be an aromatic compound, a lipid, or even a nucleic acid. The fimctions of these glycosides are as diverse as their chemical compositions, although it can be said that, in 

Some mammalian organs, particularly the liver and kidney, have the ability to convert numerous aliphatic or aromatic alcohols and carboxylic acids into their respective /3-D-glucosiduronic acids these can be transported in the blood or excreted through the urine or bile. This reaction pertains not only to such foreign substances as drugs, but also to such important endogenous compounds as steroid hormones, thyroxine, or bilirubin. 

In 1951, Dutton and Storey reported that the synthesis of o-amino-phenyl 3-D-glucosiduronic acid requires the presence of boiled liver-extract. They subsequently identified the active principle of the boiled extract as uridine 5-(D-glucopyranosyluronic acid pyrophosphate). This discovery was the first reported instance of transglycosylation from a glycosyl nucleotide. 

A large number of acceptors other than o-aminophenol may participate in this type of reaction. These include not only phenols but also 

Investigations to determine whether the transfers to the various acceptors are catalyzed by one nonspecific enzyme, or by several specific enzymes, have been hampered by the particulate (microsomal) nature of active enzyme-preparations and by lability of the preparations obtained when the microsomes are solubilized by conventional methods. However, a solubilization and purification of D-glucopyranosyluronic transferase has been achieved by treating liver microsomes with the venom of Trime-resurus flavoviridis The soluble enzyme showed activity toward phenols and carboxylic acids, but not toward aniline, indicating the existence of at least two different transferases. 

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KdENIQS KNORR Qlycosidation Synthesis of glycosides from bromosugars in the presence of Ng or Hg ... 

Koenigs-Knorr reaction (Section 25.6) A method for the synthesis of glycosides by reaction of an alcohol with a pyranosyl bromide. 

Synthesis of glycoside 138, a galactose conjugate of SIN-1 13, has been achieved and its role as /3-galactosidase-mediated nitric oxide donor has been evaluated <2005JOC3518>. 

Scheme 5.63 Use of glycals in solid-phase synthesis of glycosides.

Enzymatic Synthesis of Glycosides and Glucuronides Table 7.1 continued)... 

Several means are available for the synthesis of glycosides by application of modifications to accessible compounds. Here, only those reactions involving changes at C-1 — anomerisations and transglycosidations, will be considered. 

As outlined in CHEC-II(1996) <1996CHEC-II(7)89>, furo[2,3- j-l,3,2-dioxathioles are used mainly in the synthesis of glycosides. Position ia of these systems is susceptible to nucleophilic attack. Ytterbium-catalyzed cyanation of sulfite 53 using NaCN and Yb(OTf)3 in hexamethylphosphoramide (HMPA) at 90 °C produced glycosyl cyanide 54 (Equation 7) <20040L3913>. 

N-alkylations and rearrangements are important for the synthesis of glycosides. N-3 and N-4 glycoside, e.g., of 5-oxo-TPs, are obtained under different conditions as the kinetically and thermodynamically controlled product, respectively [75BSF(2)2561] therefore a thermal rearrangement from an N-3 to an N-4 glycoside is possible. Table X lists these glycosides included are those derived from thioxo-TPs and mercaptomethyl-TPs. 

As the chemical synthesis of glycosides is cumbersome, biotechnological transglycosidation using glycosidases is attracting more and more attention [60]. 

C. H. Wong and G. M. Whitesides, Synthesis of glycoside bonds, in Enzymes in Synthetic Organic Chemistry, Pergamon Press, Oxford, 1994, p. 252. 

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