A novel peptide conformation: the γ-bend ribbon

A gama-turn mimetic for selective sensing of Cu(II) and combinatorial multiple logic gate

We have designed and synthesized a gama-turn mimetic using fenamic acid and α-aminoisobutyricacid (Aib), the conformation and optoelectronic properties of which can be changed by appropriate external stimuli. From single-crystal...

Recent strategies used in the synthesis of saturated four-membered heterocycles

The importance and prevalance of O-, N-, and S-atom containing saturated four-membered ring motifs in biologically active molecules and potential therapeutics continues to drive efforts in their efficient synthetic preparation. In this review, general and recent strategies for the synthesis of these heterocycles are presented. Due to the limited potential bond disconnections, retrosynthetic strategies are broadly limited to cyclizations and cycloadditions. Nonetheless, diverse approaches for accessing cyclization precursors have been developed, ranging from nucleophilic substitution to C-H functionalization. Innovative methods for substrate activation have been developed for cycloadditions under photochemical and thermal conditions. Advances in accessing oxetanes, azetidines, and thietanes remain active areas of research with continued breakthroughs anticipated to enable future applications.

Uncommon Four-Membered Building Blocks - Cyclobutenes, Azetines and Thietes

Strained ring systems have gained considerable importance over the last few years for their implication in natural product syntheses or in drug discovery programs. We present herein a recollection of our work on the construction and functionalization of unsaturated four-membered carbo- and heterocycles in the context of the literature, as well as their applications in further reactions.

Stereoselective Access to Azetidine-Based α-Amino Acids and Applications to Small Peptide Synthesis

Non-natural azetidine-based amino acids (Aze) present interesting features in protein engineering. A simple organometallic route toward unsaturated carboxylic acid precursors is presented. Subsequent metal-catalyzed asymmetric reduction allowed for the synthesis of a new library of 2-azetidinylcarboxylic acids, which were finally employed in the formation of small peptide chains.

Conformational landscape of substituted prolines

The cyclic side chain of the amino acid proline confers unique conformational restraints on its backbone and side chain dihedral angles. This affects two equilibria-one at the backbone (cis/trans) and the other at the side chain (endo/exo). Substitutions on the proline ring impose additional steric and stereoelectronic effects that can further modulate both these equilibria, which in turn can also affect the backbone dihedral angle (ϕ, ψ) preferences. In this review, we have explored the conformational landscape of several termini capped mono-(2-, 3-, 4-, and 5-) substituted proline derivatives in the Cambridge Structural Database, correlating observed conformations with the nature of substituents and deciphering the underlying interactions for the observed structural biases. The impact of incorporating these derivatives within model peptides and proteins are also discussed for selected cases. Several of these substituents have been used to introduce bioorthogonal functionality and modulate structure-specific ligand recognition or used as spectroscopic probes. The incorporation of these diversely applicable functional groups, coupled with their ability to define an amino acid conformation via stereoelectronic effects, have a broad appeal among chemical biologists, molecular biophysicists, and medicinal chemists.