Uronic acids derivatives

From the reactions shown in Scheme 5, it is obvious that only those uronic acid derivatives whose elimination proceeds with the formation of enolic or aldehydic groups, or both, afford products capable of reducing the Cu(II) ion. Although such structures can be expected from hexo- and hepto-furanuronic, as well as from hep-topyranuronic, acid derivatives, glycosides of pentofuranuronic and of hexopyranuronic acid derivatives do not exhibit reducing properties. However, in view of this generalization, the zero reducing power observed for compound 26 requires a different explanation. 

Some examples of natural uronic acid derivatives... 

Uronic acid derivatives are also known among the guanosine 5 -pyrophosphate esters. A mixture of the a-D-mannopyranosyluronic acid ester (20) and, presumably, the /J-L-gulopyranosyluronic acid ester (21) was isolated from the brown alga Fucus gardneri,88 The conversion of the uronic acid in the ester 20 into D-mannitol, and that... 

Oxidation of methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside with potassium permanganate in the presence of potassium hydroxide afforded methyl 3,4-isopropylidene-2-desoxy-a-D-galacturonoside (LXXXIV) as its potassium salt. This could readily be converted into methyl 2-desoxy-a-D-galacturonoside (LXXXV) and both LXXXIV and LXXXV afforded crystalline esters and amides.230 The uronic acid derivative could be reduced by lithium aluminum hydride in ethereal solution to give methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside.230 Although 2-des-... 

Stereocontrolled ethynylation of methyl 2,3,4-tri-O-benzyl-a-D-g/Hco-hexodialdo-l,5-pyranoside (52) with a Grignard reagent formed from trimethylsilylacetylene, followed by a multistep procedure afforded the aminouronic acid 53, the a-amino acid on which miharamycin A is based.168 Uronic acid derivatives have also been produced by the Wittig reaction on the aldehydic side chain of dialdofuranose compounds.169... 

P. Kovac, J. Hirsch, and V. Kovacik, Synthesis and reactions of uronic acid derivatives. Part II. /8-Elimination reactions of some derivatives of methyl-3,4-0-isopropylidene-D-galacturonate, Carbohydr. Res., 32 (1974) 360-365. 

Scheme 13 Labeling of a disaccharide uronic acid derivative...

Methyl-,4C D-glucuronate was prepared44 from the D-glucofuran-uronic acid derivative 22 (obtained by benzylidenation of D-glu-curonic acid in the presence of zinc chloride) by treating its sodium salt with methyl-14C iodide, followed by hydrogenolysis of the ester 23 in the presence of palladium-on-carbon the infrared (i.r.) spectrum of the product was identical to that of authentic 2. 

A substantial improvement in the synthesis of steroid /3-D-glucosid-uronic acid derivatives was achieved by Conrow and Bernstein,125 who introduced cadmium carbonate as a new and effective catalyst in the Koenigs-Knorr reaction procedure its use proved to be particularly convenient in the synthesis of such derivatives of phenolic steroids, where the yields obtained by using silver carbonate had not usually exceeded 10%. Thus, by employing cadmium carbonate, several succesful syntheses in the series of phenolic steroids have been claimed (see, for example, Ref. 126). 

Reactions between D-glucuronic acid, its amide, or 6,3-lactone with various aromatic and aliphatic amines, carbamates, and their derivatives, have often been used for the preparation of (D-glucosyl-amine)uronic acid derivatives of interest as potential drug metabolites or chemotherapeutic agents however, very little evidence is available... 

A (D-glucosylamine)uronic acid derivative has been identified331 as the metabolite of carbamazepine (5//-dibenz[fe,/]azepine-5-carbox-amide, an anti-epileptic agent) by means of permethylation, g.l.c., and mass spectometry. Analytical data for the conjugate (identified in the bile of the isolated, perfused, rat liver) indicated that the carboxamide nitrogen atom is linked to C-l of the sugar moiety. 

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... 

In other approaches, the glycosidic bond is synthesized in some masked form. Thus, in Barett s reductive glycosylation [634] (Scheme 4.61), an ester bond is created first at the anomeric center using the uronic acid derivative 293. Thionation of the carbonyl group of 294 was followed by reductive desulfurization to give the disaccharide 296. 

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