Development of Novel Technologies for Efficient Peptide and Protein Synthesis

Abstract

Peptides and proteins underpin all biological function. These ubiquitous biomolecules take on a plethora of structural and functional roles in the cell, leading to intensive research efforts into understanding the fundamental nature of these biopolymers and their potential application as therapeutics. Homogeneous samples of peptides and proteins are necessary for such studies, yet many remain inaccessible in useful quantities. The chemical synthesis of these biomolecules is underpinned by ligation chemistry, with native chemical ligation being the most widely used. However, ligation chemistry suffers from two key limitations. First, there is a paucity of ligation techniques that have been applied in a scalable manner. Second, a significant portion of hydrophobic polypeptides remain inaccessible by ligation chemistry due to their poor aqueous solubility. This thesis outlines the development of novel technologies for the synthesis of peptides and proteins, focusing on overcoming these two limitations. In Chapter 2 the scalability of NCL is addressed through the application of flow chemistry to the synthesis of polypeptide therapeutics. This platform is used for the efficient preparation of the HIV fusion inhibitor enfuvirtide 45-fold faster than comparable batch methods. The diagnostic agent somatorelin is also rapidly synthesised via the largest-scale ligation in the literature, yielding over 100 mg of purified product. Chapter 3 details the development of reductive diselenide-selenoester ligation (rDSL) methodology. This rDSL reaction is the first non-templated ligation method to operate at nanomolar concentrations. This protocol allowed for the efficient synthesis of tesamorelin, a lipidated therapeutic. The methods developed herein have therefore directly addressed two critical problems in peptide chemistry, allowing ligations to be performed in a scalable manner and at low concentrations.