Chemistry of Glucoisosaccharinic Acids

The pulp and paper industries generate very large amounts of organic waste throughout the various processes of papermaking. Alpha and beta-glucoisosaccharinic acids ((2S,4S)-2,4,5-trihydroxy-2-(hydroxymethyl) pentanoic acid and (2R,4S)-2,4,5-trihydroxy-2-(hydroxymethyl)pentanoic acid) are the major components of pulp waste. They are produced in any process in which cellulosic materials are treated with aqueous alkali and constitute 30-40% of the total organic waste generated. Thus, they are potentially valuable platform chemicals with a highly functionalised carbon skeleton, with fixed chirality at C-2 and C-4, which makes them ideal starting materials for use in synthesis, instead of the current practice of burning such a valuable resource as a source of energy.

Due to the difficulties involved in isolating the 2R-epimer from the mixture and the lack of a simple and easily repeatable procedure to prepare it, to date only the chemistry of the 2S-epimer has been widely studied and only the 2S-epimer has been used in synthesis. In order to assess the potential of these saccharinic acids as platform chemicals, the protecting group chemistry of the lactone form of the alpha-glucoisosaccharinic acid was explored. The use of single and multiple step reaction pathways leading to the regioselective protection of the three different hydroxyl groups and strategies for protecting the three different hydroxyl groups individually or in pairs was explored and is reported in this thesis. These various strategies were subsequently applied to a mixture of the two epimers leading to the preparation, in a three step procedure, of 6-benzoyl-5-tert-butyldimethylsilyl-β-glucoisosaccharino-1,4-lactone, a derivative of the 2R-epimer.

An attempt to convert the 2S-epimer into the 2R-epimer through the inversion of their stereochemistry via Sharpless asymmetric dihydroxylation reactions is also reported. A maximum conversion of 52% was obtained after optimization of the procedure.