Date of Award
2024
Degree Type
Thesis
Degree Name
Master of Science in Chemistry
Department
Chemistry
First Advisor
Fang Wang
Abstract
Bioconjugation is a synthetic technique enabling the construction of a covalent bond between two molecules, at least one of which is a biomolecule.[1] Such modifications of biomolecules can impart various new functions, including modified enzymatic activity, enhanced fluorescence emission, and improved metabolic stability. Moreover, bioconjugation is applied to produce antibody-drug conjugates, a novel class of targeted therapeutics for cancer treatment.
Previous work by our group using pyridinium salts has enabled us to achieve effective cysteine arylation with rapid kinetics and remarkable selectivity. The bioconjugates produced with these reagents are susceptible to carbon-sulfur bond cleavage under certain conditions, such as at 95 °C in the presence of excess 2-mercaptoethanol, limiting the application of this chemistry. We have designed a series of meta-substituted pyridinium salts to address this issue which can potentially form more stable cysteine bioconjugates. However, the nucleophilic aromatic substitution reaction of these reagents with cysteine was relatively slow and unsuitable for effective cysteine functionalization.
To overcome this challenge, we adopted an alternative approach to arylate cysteine using para-nitropyridine-borane adducts. We found that such Lewis acid-base adducts exhibit high reactivity toward cysteine in organic solvents at room temperature, allowing complete reaction conversion at 20 mM concentrations within minutes. In addition, we identified pyridyl iodonium compounds as promising arylating reagents, which can effectively functionalize cysteine at pH 7.0 in aqueous media. We expect that these two classes of cysteine bioconjugation reactions can be expanded to enable diverse cysteine modification tasks, including the synthesis of antibody-drug conjugates and macrocyclic peptides.
Recommended Citation
Bassett, Gregory, "CYSTEINE ARYLATION VIA UNCONVENTIONAL NUCLEOPHILIC AROMATIC SUBSTITUTION" (2024). Open Access Master's Theses. Paper 2544.
https://digitalcommons.uri.edu/theses/2544
Cysteine Arylation Supporting Information