Oxidative decarboxylation of glucuronosides and the synthesis of xylitol

Jonathan A Stapley, Purdue University

Abstract

The purpose of this research was to develop a novel chemical synthesis of xylitol, which could potentially be implemented on an industrial scale. Principally, the oxidative decarboxylation of glucuronosides was pursued as a novel route to yield xylitol, although experiments with free glucuronic acid and aldonic acids were also executed. Several chemical decarboxylation techniques were studied including anodic decarboxylation, variants of the Ruff degradation, hypochlorous acid decarboxylation, and others. Anodic decarboxylation was found to be the only successful method for the desired degradation of glucuronosides. The Hofer-Moest (non-Kolbe) decarboxylation, and mechanism thereof, is submitted as the reaction of interest. As such, glucuronosides undergo a one-electron oxidation to form an acyloxy radical, which decomposes to form carbon dioxide and a C-5 radical. The radical is subsequently oxidized to a cation. The cation undergoes nucleophilic attack from the solvent (water), which product, upon spontaneous hydrolysis, yields xylo-pentodialdose. Although not effective in the decarboxylation of glucuronosides, the Ruff degradation (notably the copper variant) is considered in detail in this study. The reaction is critically reviewed and previous attempts at mechanistic description are challenged. The Hofer-Moest decarboxylation mechanism is presented as the mechanism of the Ruff degradation, and supporting evidence for such is offered. Cu(III) is submitted as the active species of the copper variant of the Ruff degradation.

Degree

Ph.D.

Advisors

BeMiller, Purdue University.

Subject Area

Food science|Organic chemistry

Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server
.

Share

COinS