Glucopyranosiduronic acids preparation

A number of /i-D-glucopyranosiduronic acids have been prepared from methyl 2,3,4-tri-O-acetyl-1 -bromo-1 -deoxy-/J-D-glucopyranuronate (85), a compound initially prepared by Goebel and Babers by the action of hydrogen bromide in acetic acid on methyl tetra-O-acetyl-a- or fi-D-glucopyranuronates.245... 

Early attempts to prepare phenyl a- and /3-D-glucopyranosiduronic acid by this reaction were not always successful.However, by performing the oxidation at a slightly higher temperature (about 90°) and at pH 8-10, and by using more catalyst, it has been found possible to obtain both compounds - the use of really fresh catalyst is also important. The following modification of the original procedure for the preparation of the or anomer has been found to improve the yield nearly four-fold. 

D-Glucosiduronic acids are of rare occurrence in plants, although in those species where they do occur they sometimes accumulate in high concentration. The mechanism of their formation in plants is undoubtedly identical with that in animals. An enzyme preparation from leaves of the French bean has been shown to catalyze the formation of quercetin-3-yl /3-D-glucopyranosiduronic acid from uridine 5-(a-D-glucopyranosyl-uronic acid pyrophosphate) and quercetin. In contrast to the liver enzyme, the transferase from beans was found to be specific for the acceptor. 

The 2-, 3-, 4-, and 6-monosulphates of methyl a-D-galactopyranoside and the 2-and 3-monosulphates of methyl a- and j8-D-glucopyranosiduronic acid have been prepared by standard methods. Sulphates or mixtures of sulphates and cyclic sulphates were produced when benzyl 2,3-anhydro-4-0-triflylpentopyranosides were treated with t-BUOSO3H. An example is presented in Scheme 15. The conversion of cyclic sulphates to epoxides is covered in Chapter 5. 

Condensation of the appropriate per-O-acetylated glycopyranosyl bromide with 4-aminobenzenethiol in the presence of sodium methoxide has been used to prepare 4-aminophenyl l-thio-j3-D-gluco-, -galacto-, and -xylo-pyranosides and 4-aminophenyl 2-acetamido-2-deoxy-1 -thio-jS-D-glucopyranoside. 4-Amino-phenyl l-thio-/3-D-glucopyranosiduronic acid was synthesized by condensation of methyl (2,3,4-tri-O-acetyI-a-D-glucopyranosyl bromide)uronate with 4-aminobenzenethiol, followed by saponification with sodium hydroxide. An attempt to obtain the l,2-ci5-l-thioaldopyranoside by reaction of 4,6-di-0-acetyl-2,3-0-carbonyl-a-D-mannopyranosyl bromide (191) with sodium 4-nitrobenzene-... 

The synthesis of some -D-glucopyranosiduronic acids of biochemical interest has not yet been achieved, and one must rely upon biosynthetic methods of preparation. 

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