Glucofuranurono-6,3-lactone

Deoxy-5-fluoro-D-glucose and -L-idose were synthesized from 1,2-(9-isopropylidene-a-D-glucofuranurono-6,3-lactone (285). Treatment of l,2-0-isopropylidene-5-0-triflyl-a-D-gluco- (286 prepared from 285) and -) -L-ido-furanurono-6,3-lactones (289 prepared from 288), with BU4NF... 

Fundamentally, D-glucofuranurono-6,3-lactone (4) contains the 2,6-dioxabicyclo[3.3.0]octane structure (5), just as do ido-, manno-, and... 

Some differences between D-glucofuranurono-6,3-lactone (4) and D-glucose as regards their respective thermodynamic stabilities and their chemistry may be generalized as follows. 

On account of the more favorable anomeric effect,12 as well as of the larger nonbonding interactions of vicinal, synclinal substituents in furanoses as compared to pyranoses, jS-D-glucofuranose,13 /3-D-glucofuranurono-6,3-lactone, and their derivatives are of higher thermodynamic stability than their respective a-D anomers. 

Because direct glycosidation of 4 with phenols is not possible, indirect methods must be used for the preparation of aryl D-glucofuranosidurono-6,3-lactones (29). In addition, aryl 2,5-di-O-acetyl-D-glucofuranosidurono-6,3-lactones (30), obtained35-37 from the reaction of 1,2,5-tri-0-acetyl-D-glucofuranurono-6,3-lactones with phenols, can only be deacetylated by such multi-step procedures as (1) ammonolysis of 30 to afford aryl D-glucofuranosiduronamides (31), followed by amide hydrolysis and lactonization, 35,37 or (2) reduction of 30 with lithium aluminum hydride, and subsequent oxidation of the intermediate aryl D-glucofuranosides38 (32) (see Scheme 1). 

There are distinct correlations between the mechanism of formation of compound 43, the eliminations frequently observed with derivatives of aldaric acids, and the reducing power of alkyl D-glucofuranosidurono- and l,2-0-alkylidene-a-D-glucofuranurono-6,3-lactones toward complexed copper(II) solutions. These phenomena are discussed in Section VII. 

Specifically, in reactions of 4 with acetic anhydride in the presence of zinc chloride58 or boron trifluoride17,35 as the catalyst, 1,2,5-tri-O-acetyl-/J-D-glucofuranurono-6,3-lactone (12) is the preponderant product in the presence of pyridine,58 however, acetylation of 4 by acetic anhydride leads to the favored formation of the corresponding a-D anomer. In contrast to acetylations, in benzoylation reactions, the ratio of anomers apparently changes. Thus, on treatment of 4 with benzoyl chloride in pyridine, Momose and coworkers17 isolated... 

In view of the great preponderance of the 3-d anomer in crystalline D-glucofuranurono-6,3-lactone (4), the results obtained from its acetylation with acetic anhydride-pyridine disagree with observations59 suggesting that anomeric ratios are not altered during acylation in pyridine. 

Proton Coupling-Constants of Methyl fi- (25) and a-D-Glucofuranosidurono-6,3-lactone (26), and l,2-0-Isopropylidene-a-D-glucofuranurono-6,3-lactone (33)... 

VI. Reactions Involving the Lactone Ring of Derivatives of d-Glucofuranurono-6,3-lactone... 

A very low yield of l,2-0-isopropylidene-5-0-p-tolylsulfonyl-o -D-glucofuranuronamide was obtained113 on ammonolysis of the corresponding 5-O-p-tolylsulfonyl lactone (52) with ammonia in methanol at low temperature. In a similar reaction of l,2-0-isopropylidene-5-0-(methylsulfonyl)-a-D-glucofuranurono-6,3-lactone (50), formation of substantial proportions of l,2-0-isopropylidene-5-0-(methylsul-fonyl)-Q -D-glucofuranuronamide could be observed110 in the reaction mixture however, on evaporation, the starting material was reformed. 

On reaction with hydroxylamine in the presence of appropriate bases, such derivatives of D-glucofuranurono-6,3-lactones as 25, 26, and 33 form114 N-hydroxyamides. On the other hand, when treated with hydroxylamine without base catalysis, compound 4 yields115 aWeJjt/do-D-glucurono-6,3-lactone oxime. 

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