Approaches to High Throughput Physical Organic Chemistry
Over the past ten years, the development of High Throughput (HT) synthetic chemistry techniques has allowed the rapid preparation of libraries of hundreds to thousands of compounds. These tools are now extensively used for drug and material discovery programmes. The subsequent development of analytical capabilities to carry out qualitative and quantitative assessment of the compounds generated by HT synthesis as well as their HT screening has led to a dramatic broadening of the scope of HT techniques, ranging from image based analysis techniques to mass spectrometry (MS). Based on the latter, a range of solid phase and solution phase analytical constructs was developed to enable the qualitative and quantitative assessment of mixtures of small compounds, using positive electrospray MS as the sole analytical tool. A version of the construct allowed HT reactivity profiling to be carried out on a range of ten carboxylic acids, ten aldehydes and ten isonitriles in the Ugi 4-component condensation reaction. The effect of various parameters such as the concentration of the monomers on the reactivity was investigated. The elaboration of a HT Hammett parameter assessment method was made possible by the development of an electrophilic version of the construct. The value of the Hammett value was afforded by means of combinatorial Hammett plots and values were successfully evaluated in a HT mode for around thirty anilines with substituents in the meta and para position of the aromatic ring. Finally, analytical constructs were used in an attempt to evaluate enzyme reaction kinetics via the labelling of peptides and small drug fragment with coded constructs, to afford affinity determinations between the enzyme (protease) and peptidic or fragment based substrates.