Energetics of oxo- and thio-dipeptide formation via amino acid condensation: a systematic computational analysis

Abstract

Oxo-dipeptides and thio-dipeptides are built via condensation between couples of amino acids and amino thioacids, the latter with the carbonyl oxygen replaced by an sp(2) sulfur. We explored via in silico methods (PBE0/6-31G(d,p) and PBE0/6-311G(d,p)) all the possible combinations and built 800 dipeptides, whose structures were fully optimized. Maps of condensation energies are presented to highlight optimal partners leading to stable dipeptides and critical situations for which lower stability or instability is predicted in terms of Gibbs reaction free energies. To validate the feasibility of our computational investigation, we synthesized and compared the stabilities of two thionated dimers, namely -Gly[Ψ(CSNH)]Gly- and -Phe[Ψ(CSNH)]Phe-, characterized by diverging physico-chemical properties. To the best of our knowledge, this is the first systematic analysis reported for dipeptides built from natural amino acids as well as for their corresponding thio-analogs.

Chemoselectivity and the Chan–Lam Coupling Reaction: Adding Amino Acids to Polymer-Coated Microelectrode Arrays

“…The crude mixture was purified via column chromatography using 3/1 CH 2 Cl 2 /acetone to acquire the desired product in a 90% yield (240 mg; MW = 222.26 g/mol). The spectral data were consistent with previously published data …”

Endothioxopeptides: A conformational overview

“…Additional publications of interest in this area include: (i) A systematic computational study of the energetics of the thionated ‐Glyψ[CSNH]Gly‐ and ‐Pheψ[CSNH]Phe‐ dipeptide formation via amino acid condensation . (ii) A theoretical investigation of (a) the cis / trans isomerism in thionated peptoids (N‐substituted Gly residues) and β‐peptides (increase of the cis isomer preference), and (b) their thionamide…aromatic (linked to the αN) interactions, through C sp 2 H…S (thionamide) H‐bonding, which stabilize selected peptoid conformations .…”