Abstract
In the title compound, phenyl (S)-2-[(S)-(1-{2-[(S)-(1-{[(tert-but-oxy)carbon-yl]amino}-bicyclo-[2.2.2]octan-2-yl)formamido]-propanamido}-bicyclo-[2.2.2]octan-2-yl)formamido]-3-phenyl-propano-ate chloro-form monosolvate, C42H56N4O7·CHCl3, the α,β-hybrid peptide contains two non-proteinogenic amino acid residues of (S)-1-amino-bicyclo-[2.2.2]octane-2-carb-oxy-lic acid [(S)-ABOC], two amino acid residues of (S)-2-amino-propanoic acid [(S)-Ala] and (S)-2-amino-3-phenyl-propanoic acid [(S)-Phe], and protecting groups of tert-but-oxy-carbonyl (Boc) and benzyl ester (OBn). The tetra-mer folds into a right-handed mixed 11/9 helix stabilized by intra-molecular i,i+3 and i,i-1 C=O⋯H-N hydrogen bonds. In the crystal, the oligomers are linked by N-H⋯O=C hydrogen bonds into chains along the a-axis direction. The chloro-form solvent mol-ecules are inter-calated between the folded chains via C-H⋯O=C inter-actions.
Highlights
Chemical contextThe title compound is an ,-hybrid tetrapeptide with alternating proteogenic -amino acid and ABOC residues. (S)-1aminobicyclo[2.2.2]octane-2-carboxylic acid [(S)-ABOC] is a
Université de Lorraine, UMR 7036 CRM2, Vandoeuvre-lès-Nancy, France, bCNRS, UMR 7036 CRM2, Vandoeuvre-lèsNancy, France, and cIBMM, UMR 5247 CNRS-Université Montpellier–ENSCM, 15 avenue Charles Flahault, 34093
The oligomers are linked by N—H O C hydrogen bonds into chains along the a-axis direction
Summary
The title compound is an ,-hybrid tetrapeptide with alternating proteogenic -amino acid and ABOC residues. (S)-1aminobicyclo[2.2.2]octane-2-carboxylic acid [(S)-ABOC] is a. The title compound is an ,-hybrid tetrapeptide with alternating proteogenic -amino acid and ABOC residues. 2,3,3-trisubstituted bicyclic amino acid which exhibits a high propensity to induce both a reverse turn into short peptides and helices in oligoureas and in ,-hybrid peptides (Songis et al, 2007; André et al, 2012, 2013; Legrand et al, 2012, 2014). In our last study we showed that short oligomers adopted an 11/9 helix, whereas an 18/16 helix was favored for longer oligomers in solution. NMR studies suggested a rapid interconversion between the 11/9 helix and the 18/16 helix for oligomers of intermediate length. Only the 11/9 helix has been observed whatever the length of the oligomers capped by an iPrCO and an OBn group (Legrand et al, 2014)
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