Sugar moiety formation

Certain kinds of metal ions bind to the DNA double strands by an electrostatic interaction with the phosphate group(s) or by complex formation with the sugar moiety or the nucleic... 

Harris has studied the complexa-tion of neomycin with pectin and demonstrated the inhibition of complex formation in the presence of an electrolyte. Potentiometric measurements indicate the mechanism of the reaction to be a cation-anion interaction. H-bonding between the hydroxy groups of pectin and sugar moieties of neomycin has been suggested and would further stabilise the compound. 

A rapid synthesis of cyclodepsipeptides containing sugar moieties was reported by Zhu and coworkers (Scheme 20) [88]. A three-component reaction of a sugar amino acid derivative 20a, an aldehyde b, and a dipeptide isocyanide c, followed by saponification and trifluoroacetic acid-promoted macrocyclization was employed to afford the cyclic amino sugar cyclopeptides d. This approach allows to systematically modify the amino acids and the carbohydrate residue, as well as the size of the macrocycle. Again, the only reagents used to mediate the formation of the... 

Sulfation of the sugar moieties of chondroitins occurs by a sequence of steps, the first of which involves formation of 3 -0-phosphono-5 -adenylyl hydrogen sulfate, the sulfate donor.346,347 This enzyme is present in a number of the tissues in which these glycoproteins... 

Occurrence in nature of branched-chain carbohydrates has prompted interest in the syntheses of these complex structures and stimulated the preparation of analogues for biological evaluation. Consequently, new methods for the construction of these particular skeletons have been devised [1]. The use of carbohydrates as a cheap source of chiral starting materials [2-4] for the synthesis of complex, nonsugar molecules has prompted the emergence of new imaginative methods for formation of carbon-carbon bonds adapted to the particular reactivity of sugar moieties. 

Technically, the addition of carbon-centered radicals to C-N double bonds is as yet of little if any importance. In the free-radical chemistry of DNA it plays, however, a considerable role in the formation of the C(5 )-C(8) linkage between the sugar moiety and the purines (Chap. 10.5). Because of its importance, even an immune assay has been developed for the sensitive detection of this kind of damage in DNA (Chap. 13.2). The addition of the C(5 ) radical to the C(8) position of a purine is obviously facilitated for steric reasons (formation of a six-membered ring), but the same kind of reaction also occurs as an intermolecular reaction. Since alkyl radicals are nucleophilic, the rate of this reaction is noticeably increased upon protonation of the purine (Aravindakumar et al. 1994 for rate constants see Chap. 10.5). 

The release of free base (see also Hoffman and Huttermann 2000) and the formation of 2-dRL results from a damage of the sugar moiety, but there are a host of... 

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