Automated Orthogonal Deprotection of Glu(OAllyl) and Peptide Stapling via Lactamization

Introduction

Peptidyl side-chain functionalizations, such as bioconjugation, branching, and cyclization, are impactful and essential synthetic tools, necessary for pharmaceutical development, medical imaging, materials research, and more. Many amino acid residues can serve as sites for side-chain functionalization, including glutamic acid.

To demonstrate the Liberty Blue automated peptide synthesizer’s ability to efficiently synthesize and functionalize peptides, branched and lactam-stapled variants of the HIV-1 antibody epitope gp41_659-671 (ELLELDKWASLWN) and Afamelanotide (Ac-SYSNleEHDFRWGKPV-NH₂) were synthesized. For branched variants, H-Ala-OtBu was coupled to the orthogonally deprotected Glu side-chain. For cyclized variants, Lys(Alloc) was incorporated into the linear synthesis and simultaneously deprotected with Glu(OAllyl) prior to lactamstapling.