Vincent Aucagne

Rotaxane-based propeptides: protection and enzymatic release of a bioactive pentapeptide.

Ring of protection: A [2]rotaxane 1 protects and selectively releases a bioactive pentapeptide. The rotaxane macrocycle provides a defensive shield that very significantly improves the poor stability of the peptide to both individual peptidases and the cocktail of enzymes present in human plasma. Glycosidase-catalyzed cleavage of a carbohydrate ‘stopper’ in the rotaxane triggers release of the parent peptide

Synthesis of a Biologically Active Triazole‐Containing Analogue of Cystatin A Through Successive Peptidomimetic Alkyne–Azide Ligations

Amide surrogates are common in naturally occurring peptides and in synthetic peptides used in therapy. Whereas backbone-engineered proteins are, to date, extremely laborious to produce by genetic means, the advent of chemoselective peptide chemical ligation reactions paved the way to such complex molecular architectures of considerable potential for protein therapeutics. To date, the most popular strategy to introduce amide bond surrogates in proteins relies on an elaborate combination of 1) solutionphase synthesis to provide a suitably protected pseudo-dipeptide, 2) solid-phase peptide synthesis (SPPS) to incorporate the modification in a peptide fragment, and 3) native chemical ligation (NCL) to yield a full-length backbone-engineered protein. A valuable alternative for the introduction of amide-bond mimics in proteins would be a peptidomimetic ligation strategy combining in a single step the formation of the amide surrogate, its incorporation in a peptide backbone, and ligation of fragments. Besides the pioneering study on thioester backbone-engineered proteins, only few examples have been reported, including a recent study concerning a ligation of thioacidand aziridine-terminated model peptides, giving a reduced form (Y[CH2NH2]) of an amide bond. To enlarge the palette of the synthetic protein chemist, we envisioned developing a new peptidomimetic ligation prototype that leads to bioactive backbone-modified proteins. Herein, we report for the first time the use of the Cu-mediated cycloaddition of azides and terminal alkynes (CuAAC) for the assembly of unprotected peptide fragments into a bioactive triazole-containing protein.

Towards the Simplification of Protein Synthesis: Iterative Solid‐Supported Ligations with Concomitant Purifications

Please release me: a new linker for the temporary tagging of peptides at their N-terminus after solid-phase elongation, and its potential for capture/release purification is demonstrated. This concept is extended to a remarkably efficient self-purifying N-to-C iterative triazole ligation strategy, which is applied to the synthesis of a polypeptide having 160 residues, in a high purity without the need for chromatographic purification (orange blocks: peptide segments).

Highly efficient solid phase synthesis of large polypeptides by iterative ligations of bis(2-sulfanylethyl)amido (SEA) peptide segments

Up to now, the advantages of solid phase protein synthesis have been largely under-utilized due to the difficulty of designing a simple and efficient elongation cycle enabling the concatenation of unprotected peptide segments. The combination of selective N-terminal anchoring (N3-Esoc linker) with the blocked thioester properties of the SEAoff group enabled the solid phase concatenation of unprotected peptide segments by N-to-C sequential formation of native peptide bonds. The strategy was applied to the synthesis of a 60 amino acid-long latent peptide thioester or to the assembly of five peptide segments to give a 15 kDa polypeptide.

Solid phase oxime ligations for the iterative synthesis of polypeptide conjugates

Peptide-based complex biomacromolecules are now optimally assembled by sequential ligation of unprotected peptide segments. However, this approach is still limited by the laborious chromatographic purification and handling steps needed for multiple successive chemoselective couplings, which leads to loss of material. An efficient alternative is solid phase chemical ligation (SPCL) initially developed for native chemical ligation. We report here an extension of this approach to iterative oxime ligation reactions, and describe a streamlined approach for the modular preparation of oxime-containing polypeptides. In particular, we determined optimal conditions to remove the Aloc group in the presence of aminooxy and oxime ether groups, and we extended the applicability of iterative C-to-N SPCL through simplification of the access to a C-terminally-grafted, unprotected peptide segment, using solid supported chemical transformations only. The high purity of the crude oxime-containing polypeptides highlights the efficiency of our approach.