Design and Synthesis of Boronolectin Fluorescence Sensors

Abstract

This thesis reports on the use of the element boron in organic chemistry. Its role in catalysis, as well as its broad utility when in the form of a boronic acid functional group is demonstrated. Boric acid and boronic acids have applications in numerous kinds of chemical reactions as catalysts. Boric acid is demonstrated in this work to catalyse the esterification of a- hydroxycarboxylic acid starting materials, including carbohydrates, typically in excellent yield. A series of reactions were conducted to demonstrate the utility and limitations of this technique. Included in this work is the synthesis of the carbohydrate, KDO. Furthermore, a series of esters were generated using salicylic acid as a starting material, one of which was subjected to x-ray crystallographic studies. Also in this thesis a novel type of boronic acid catalysed amide forming reaction is described. The reaction is shown to proceed rapidly under mild reaction conditions with little purification required to give a pure product. Structural identification of the amide products is discussed and hypothesised molecular configurations are presented. Fluorescence sensors are described as a practical application of boron – polyol interactions. Supporting theories are outlined and published work is summarised, compared and contrasted. The carbohydrates sialic acid and KDO are identified as molecular targets for boronic acid based fluorescence sensors. The benefits of multiple binding sites and optimised molecular geometry are clearly shown in the results of fluorescence assays. Sensor molecules reported in this thesis demonstrated selective binding to the carbohydrates, sialic acid and KDO.