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Oligomers that contain both alpha- and beta-amino acid residues in a 1:1 alternating pattern have recently been shown by several groups to adopt helical secondary structures in solution. The beta-residue substitution pattern has a profound effect on the type of helix formed and the stability of the helical conformation. On the basis of two-dimensional NMR data, we have previously proposed that beta-residues with a five-membered ring constraint promote two different types of alpha/beta-peptide he

We report the first high-resolution structural data for the 14/15-helix, a secondary structure that is formed by oligomers with a 1:1 alternation of α- and β-amino acid residues. Previously, we concluded from NMR data that short α/β-peptides containing cyclopentane-constrained β-residues display rapid interconversion between two helical folding patterns, the 11-helix ( i, i +3 C O···H−N H-bonds) and the 14/15-helix ( i, i +4 C O···H−N H-bonds). Subsequent work in other laboratories, however, has

Oligomers containing both alpha- and beta-amino acid residues ("alpha/beta-peptides") are intriguing as potential foldamers. A large set of alpha/beta-peptide backbones can be generated by combining alpha- and beta-amino acid residues in different patterns; however, most research to date has focused on the simplest pattern, 1:1 alpha:beta. We have begun to explore the range of variation that can be achieved with alpha-residue/beta-residue combinations by examining the folding behavior of oligome

Twisted (crystal)sisters: The structures of the α/β-peptide 11/9-helix were determined by single-crystal X-ray crystallography. The racemic compounds adopt centrosymmetric crystal packing, and display fully folded 11/9-helical conformations. The helical parameters of the 11/9-helix are analogous to those of the 310-helix, despite different hydrogen-bonding types. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer

Helices are the most extensively studied secondary structures formed by β-peptide foldamers. Among the five known β-peptide helices, the 12-helix is particularly interesting because the internal hydrogen bond orientation and macrodipole are analogous to those of α-peptide helices (α-helix and 3(10)-helix). The β-peptide 12-helix is defined by i, i+3 C═O···H-N backbone hydrogen bonds and promoted by β-residues with a five-membered ring constraint. The 12-helical scaffold has been used to generate

We present the first examples of atomic-resolution crystal data for the β-peptide 12/10-helix from oligomers of cis-2-aminocyclohexane carboxylic acid (cis-ACHC) with alternating chirality. The local conformations of two enantiomeric cis-ACHC dimer units suggested that a chiral β-peptide may adopt both right-handed and left-handed helical conformations in solution. To probe the conformational behavior of 12/10-helical β-peptides, the two reference helices with a single handedness were synthesize

Abstract (1 R ,2 S )‐2‐Aminocyclohexanecarboxylic acid ( cis ‐ACHC) is a preorganized β‐amino acid. cis ‐ACHC favors two conformations that feature gauche conformations about the C α –C β bond with torsion angles of opposite signs. The diastereomeric β‐amino acid trans ‐ACHC has been widely studied as a foldamer building block, but cis ‐ACHC has received less attention in this regard. We examined the conformational behaviour of three types of oligomer: (1) homooligomers of cis ‐ACHC, (2) β‐pepti

α/β-Peptides with alternating α-amino acid and cis-2-aminocyclohexanecarboxylic acid (cis-ACHC) residues adopt 11/9-helical conformations, the folding propensity of which decreases as the solvent polarity increases. We report a new cis-ACHC analogue, cis-2-amino-cis-4-methylcyclohexanecarboxylic acid, which significantly stabilizes the 11/9-helix propensity in protic solvents.

αβα-Tripeptide that contains a cyclic β-amino acid with an eight-membered ring, a cis-2-aminocyclooct-5-enecarboxylic acid (cis-ACOE) or a cis-2-aminocyclooctanecarboxylic acid (cis-ACOC) displayed an 11/9-helical turn in the crystal state. The related α/β-peptide oligomers were shown to adopt 11/9-helical conformations in solution.

<italic>cis</italic>-2-Aminocyclohex-4-enecarboxylic acid can promote the α/β-peptide 11/9-helix in solution and in the crystal state.

-residue in the 11/9-helical structure had a slight destabilizing effect, which could be compensated by a longer peptide sequence with more cyclic β-residues. These results provide a guidance for incorporating functional groups into an 11/9-helical α/β-peptide backbone to design functional oligomers.

Mit Röntgen-Kristallographie wurden Strukturen der α/β-Peptid-11/9-Helix bestimmt. Die racemischen Verbindungen zeigen eine zentrosymmetrische Kristallpackung mit vollständig gefalteten 11/9-Helixkonformationen. Abgesehen von den unterschiedlichen Wasserstoffbrücken sind die Parameter der 11/9-Helix analog zu denen der 310-Helix. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized

We explored trans - and cis -2-aminocycloheptanecarboxylic acid (ACHpC) as potential building blocks for helical foldamers. trans -ACHpC does not show sufficient folding propensity in unnatural peptides. cis -ACHpC promotes nontraditional helices of two unnatural peptide backbones: the 11/9-helix for 1:1 α/β-peptides and the 12/10-helix for β-peptides with interconvertible handedness. The two opposite-handed 12/10-helices rapidly interconvert in solution by pseudorotation of the two twist chair