Uronic Acid Nucleosides

Nucleoside 5 -uronic acids. Na-periodate and aq. S -RuClg added to a soln. of 2, 3 -0-isopropylidene-6-azauridine in aq. 70%-acetone, stirred 4 hrs. at room temp., and the resulting intermediate refluxed 5 hrs. in aq. 80%- acetic acid 6-azauridine-5 -uronic acid. Y 77.5%. H. Pischel, A. Hol, and G. Wagner, Coll. 59, 3773 (1974). 

The c.i.m.s. of a fully methylated D-mannuronic acid derivative is reported in Chapter 22, and some nucleoside uronic acid compounds are described in Chapter 20. 

Octosyl Acids. Three octosyl uronic acid nucleosides, produced by S. cacaoi sub sp. asoensis are shown in Figure 3. The biosynthesis of (172) and (173) has been reported (1). The replacement of the pyrimidine chromophore of (171) with adenine results in a nucleoside analogue that is a competitive inhibitor of cAMP. 

D-Glucofuranosylamine)uronic acids attained biological significance after nucleoside antibiotics containing hexuronic acid residues were isolated from natural sources examples are gougerotin and blasticidin S. 

Purine and pyrimidine nucleosides of AZT (Zidovudine, 3 -azido-3 -deoxythymidine) with [RuO ] (from RuClj/K S O/aq. M KOH) gave l-((3-azido-2,3-dideoxy-P-D-eryf/tro-pentafuranosyl-5-uronic acid)-thymine (Fig. 2.11) [335]. 

The ion-exchange separation usually affords individual fractions of structurally related glycosyl esters of nucleoside pyrophosphates, containing the same nucleotide residue, but differing in the structure of the glycosyl groups. Separation of the esters of N-acetylhexos-amines, uronic acids, and neutral monosaccharides from one another is also usually achieved. 

The most efficient photosubstitution reaction, with many applications in synthesis, is the photobromination method developed by FERRIER s group [24]. The substitution of H-5 is regioselective and stereoselective for pentopyranosides [25], hexo-pyranosides [26], 1-6 anhydrosugars [27], uronic acids [24, 28] heterocyclic derivatives from deoxyinosones [29], nucleosides [30, 31], etc.. . using bromine or N-bromo-succinimide in carbon tetracloride under irradiation. 

The use of the hypervalent iodine reagent [bis(trifluoroacetoxy)iodo]benzene has been reported to be effective in the synthesis of C-nucleoside-like compounds. Radical decarboxylation of a suitably protected uronic acid, initiated photochem-ically, followed by addition of a heterocyclic base provided the C-nucleoside in high yield.154 The mode of action involves initial radical formation of 122 (Scheme 33), followed by introduction of the base and radical coupling.155 The anomeric selectivity was high in some examples, and low in others—lepidine gave the highest proportion of the ( anomer. Isolated yields were poor to moderate. 

Compound added Distribution of 14C in nucleoside Distribution of, 4C in uronic acid ... 

Other oxidative methods have also been investigated. Thus, oxidation of the nucleosides at C-5 with chromium trioxide-pyridine,346 chromium trioxide-acetic acid,347 or periodate in aqueous acetone containing ruthenium trichloride,348 to give the corresponding uronic acid derivatives, has also been reported. 

The foregoing compounds were all prepared from preformed, nucleoside molecules alternatively, coupling of the uronic acid derivative with a heterocyclic base has also been used. Thus, Kishikawa and... 

Isono, K, Crain, P F, McCloskey, J A, Isolation and structure of octosyl acids. Anhydrooctose uronic acid nucleosides, J. Am. Chem. Soc., 97, 943-945, 1975. 

A nucleoside pyrophosphoric ester of this uronic acid, UDP-d-galacturonic acid, was shown to be present in mung beans. " In this plant were also found enzymes that led to the formation of this uronic acid derivative of a nucleoside pyrophosphate by the following pathway ... 

As this glycuronan is a mixture of two polymers, one consisting of D-mannuronic acid residues and the other of L-guluronic acid residues, it was suspected that this brown alga contains the nucleoside diphosphate uronic acid precursors from which this mixed glycuro-... 

The reverse C-nucleoside 740 of this type was obtained either by oxidative cyclization of hydrazone 739 or by one-step reaction of the uronic acid derivative 741 with lithium benzoylaminophosphinimine (72HCA2816) (Scheme 199). 

Only 2-pyridyl reverse C-nucleosides are known. Coupling saccharide free radicals 831 and 834 with protonated pyridine derivatives gave the 2-pyridyl reverse C-nucleosides 832 and 835, respectively. Free radical 831 was obtained by decarboxylative photolysis of the uronic acid derivative 830 in the presence of hypervalent iodine compounds (92TL7575 (Scheme 232), whereas free radical 834 was obtained by thermal homolysis of the carbon-iodine bond in the 6-iodo-6-deoxy-o-galactopyranose derivative 833 in the presence of benzoyl peroxide (93JOC959) (Scheme 233). 

A review has been published, in Russian, on uronic acid nucleosides as a component of natural antibiotics. The compound with the originally-proposed structure of diacetyl neosidomycin has been prepared, although the structure of neosidomycin has since been revised (see Vol. 28, p. 254). ... 

Nucleosides of Unsaturated Sugars, Ketosugars and Uronic Acids... 

Nucleosides and Unsaturated Sugars, Keto-sugars, and Uronic Acids C-Nucleosides... 

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