Boronic Acid Chemistry as a Modern Platform in Catalysis, Stereocontrolled Synthesis and Bioconjugation

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With discoveries like pharmaceutical drugs, insecticides, polymers, and food additives, organic synthesis stands as a powerful science that helped our modern society enjoy a dramatic increase in life expectancy and standard of living in the past century. Boronic acids are stable and relatively non-toxic boron-containing organic compounds that have undergone huge developments only over the past two decades. Continued growth in their synthetic and biological applications will occur only if supported by a judicious exploration of their properties and reactivity. With this view, new projects will be undertaken in the following directions: 1. Synthetic methodology development, with a focus on stereoselective synthesis to enable the selective preparation of "mirror image" forms of chiral (unsymmetrical) compounds, an endeavor of critical importance in the pharmaceutical industry. To this end, we will address the challenge of preparing highly functionalized heteroatom-containing chiral alkylboronic esters, and optimize methods for their stereoselective catalytic cross-coupling as a means to streamline the synthesis of chiral drugs. 2. New catalytic processes: We will examine new applications of boronic acids as mild and 'green' catalysts for direct elimination and substitutions of readily available alcohols, thus bypassing the use of toxic alkyl halides in these important classes of reactions. The discovery of borate-based catalytic leaving groups for primary alcohols is a high-risk-high-reward objective that would address many green chemistry “priority areas” of pharmaceutical chemistry. 3. Novel bioorthogonal conjugation chemistry with native peptides: Boronate formation with rigid diols provides a bioorthogonal “click” reaction with non-toxic components. Using two different approaches: phage display selection of peptide libraries, and rational design of heteropolycyclic boronate adducts, we will identify short and unique natural peptide sequences with a tight binding affinity to ortho-formyl arylboronic acids. Such peptides could be incorporated readily into a protein of interest due to its genetic encodability, thus providing a simple, fast and biocompatible conjugation system with labeled boronic acids that would be of great utility for investigating protein function in living systems in real time.