Glucofuranosidurono-6,3-lactone oxidation

Methyl cc-D-glucofuranosidurono-6,3-lactone (26) may be obtained exclusively by reaction of 4 with trimethyl orthoformate in the presence of boron trifluoride etherate.28 Its 2,5-dimethyl ether (27) is formed by methyl iodide-silver oxide methylation29,30 (Purdie-Ir-... 

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). 

The anomeric, methyl /3-D-glycoside lactone has also been synthesized by methylation of methyl /3-D-glucofuranosidurono-6,3-lactone.24 Trimethyl glucurone, formed by methylation of D-glucuronolactone with methyl iodide and silver oxide, is usually accompanied by some 2,5-di-O-methyl-A D-glucaro-b,3-lactone methyl ester ( trimethyl glucuralone ), an oxidation product. 

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