21.11.7 Chemoselective Ligation Methods Based on the Concept of Native Chemical Ligation

This chapter extends from the earlier Science of Synthesis contribution on peptide synthesis (Section 21.11) and focuses on recent developments in chemoselective ligation chemistry based on the logic of native chemical ligation. Synthetic strategies that broaden the scope and versatility of the ligation reaction and that have been widely adopted for the preparation of homogeneous peptides and proteins are highlighted. Methods enabling the efficient preparation of peptide ligation precursors are also included in this chapter.

Rapid Glycoconjugation with Glycosyl Amines

Conjugation of unprotected carbohydrates to surfaces or probes by chemoselective ligation reactions is indispensable for the elucidation of their numerous biological functions. Especially the reaction with oxyamines leading to the...

Wittig reagents for chemoselective sulfenic acid ligation enables global site stoichiometry analysis and redox-controlled mitochondrial targeting

Triphenylphosphonium ylides, known as Wittig reagents, are one of the most commonly used tools in synthetic chemistry. Despite their considerable versatility, Wittig reagents have not yet been explored for their utility in biological applications. Here, we introduce a new chemoselective ligation reaction that harnesses the reactivity of Wittig reagents and the unique chemical properties of sulfenic acid, a pivotal post-translational cysteine modification in redox biology. The reaction, which generates a covalent bond between the ylide nucleophilic α-carbon and electrophilic γ-sulfur is highly selective, rapid, and affords robust labeling under a range of biocompatible reaction conditions, including in living cells. We highlight the broad utility of this conjugation method to enable site-specific proteome-wide stoichiometry analysis of S-sulfenylation, visualize redox-dependent changes in mitochondrial cysteine oxidation, and redox-triggered TPP generation for controlled delivery of small molecules to mitochondria.

Chemoselective 18F-incorporation into pyridyl acyltrifluoroborates for rapid radiolabelling of peptides and proteins at room temperature

A new prosthetic group is reported for quantitative 18F-labelling of peptides and proteins based on the chemoselective ligation of potassium acyltrifluoroborates (KATs) and hydroxylamines without any detectable 18F/19F isotope exchange at the KAT moiety.

Glycoconjugate synthesis using chemoselective ligation

Chemoselective ligation of carbohydrates and polypeptides was achieved using an adipic acid dihydrazide cross-linker.

Chemoselective ligation reaction of N-acetylglucosamine (NAG) with hydrazide functional probes to determine galactosyltransferase activity by MALDI mass spectrometry

A perfluorocarbon-modified gold surface is used to immobilize PF-β-NAG and allows quantification of β-GT enzymatic activity with MALDI-TOF/MS.