2016
DOI: 10.1002/psc.2957
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En route towards the peptide γ‐helix: X‐ray diffraction analyses and conformational energy calculations of Adm‐rich short peptides

Abstract: We performed the solution-phase synthesis of a set of model peptides, including homo-oligomers, based on the 2-aminoadamantane-2-carboxylic acid (Adm) residue, an extremely bulky, highly lipophilic, tricyclic, achiral, C -tetrasubstituted α-amino acid. In particular, for the difficult peptide coupling reaction between two Adm residues, we took advantage of the Meldal's α-azidoacyl chloride approach. Most of the synthesized Adm peptides were characterized by single-crystal X-ray diffraction analyses. The result… Show more

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Cited by 8 publications
(10 citation statements)
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References 104 publications
(196 reference statements)
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“…The helical structures are stabilized by two successive intramolecular 12‐membered hydrogen bonds between the residues i and i +3. Similarly, the helical structures stabilized by the two consecutive H‐bonds have been observed in the α‐tripeptides of sterically constrained α‐amino acids . The two amide NH protons at the N ‐terminus and two carbonyl groups at the C ‐terminus of P1 and P2 are involved in the head‐to‐tail intermolecular H‐bonding with other helices in the crystal packing.…”
Section: Figurementioning
confidence: 69%
“…The helical structures are stabilized by two successive intramolecular 12‐membered hydrogen bonds between the residues i and i +3. Similarly, the helical structures stabilized by the two consecutive H‐bonds have been observed in the α‐tripeptides of sterically constrained α‐amino acids . The two amide NH protons at the N ‐terminus and two carbonyl groups at the C ‐terminus of P1 and P2 are involved in the head‐to‐tail intermolecular H‐bonding with other helices in the crystal packing.…”
Section: Figurementioning
confidence: 69%
“…Previously, conformational energy calculations using density functional theory [performed using the B3LYP functional combined with the 6‐31 + G(d,p) basis set] had predicted that after the most stable consecutive γ‐turn conformer, Ac‐(Adm) 2 ‐NHMe could adopt a distorted type‐II (II′) β‐turn with backbone torsion angles differing less than 10° from those found for tripeptide 4d . This nonhelical type of turn had however not been previously reported experimentally for N‐acyl Adm dipeptide amide sequences.…”
Section: Resultsmentioning
confidence: 90%
“…The diamondoid 2‐aminoadamantane‐2‐carboxylic acid (Adm) residue has shown intriguing potential for adopting the relatively uncommon γ‐turn conformation in X‐ray diffraction studies of short Adm‐rich peptides and homo‐peptides . In solution, Adm derivatives and dipeptides, such as Ac‐Adm‐NHMe (Ac, acetyl; NHMe, methylamino) and Ac‐Adm‐Gly‐NHMe, have been suggested to fold in γ‐turn conformations based on NMR and IR absorption spectroscopic studies.…”
Section: Introductionmentioning
confidence: 99%
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“…We wished in particular to discover and investigate in detail noncoded α‐amino acids with a high propensity to fold into single turns, and possibly offering a good chance to create new, longer ordered secondary structures. To this end, we especially considered two C α ‐tetrasubstituted α‐amino acids as potentially very promising building blocks, the chiral (αMe)Aze (Figure ) and the achiral 2‐aminoadamantane‐2‐carboxylic acid . In particular, by examining a series of repeating, homochiral , sequential ‐( S )‐(αMe)Aze‐( S )‐Ala‐ dipeptides, we found a novel stable peptide conformation, the γ‐bend ribbon structure, characterized by only half of the CO … HN intramolecular H‐bonds typical of the γ‐helix because the strong γ‐bend inducer (αMe)Aze, which forms Xxx‐(αMe)Aze tertiary amides, lacks the NH donor function.…”
Section: Introductionmentioning
confidence: 99%