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Porous crystals have great potential to exert space-specific functions such as multipoint molecular recognition. In order to rationally enhance the porous function, it is necessary to precisely control molecular recognition event in the pores. Hydrogen bonding is an effective tool for controlling molecular recognition. However, multiple hydrogen bonds, which are essentially the origin of high complementarity and specificity, remain difficult to innovate in porous crystals in an intelligent way. This paper demonstrates molecular recognition of amino acid and peptide derivatives by multipoint hydrogen bonding in a porous metal-macrocycle framework revealed by single-crystal X-ray diffraction analysis. l-Serine residues are site-selectively and residue-specifically adsorbed on the pore surface via multiple hydrogen bonds. A serine derivative is diastereoselectively recognized on the (P)- or (M)-side of the enantiomeric pore surface. Moreover, the conformation of the peptide is highly regulated, incorporating a poly-l-proline type I helix-like structure into the pore. These findings will bring deep scientific knowledge to the design of new porous crystals and functions., (© 2021 Wiley-VCH GmbH.)

Aiming at precisely arranging several proteinogenic α-amino acids on a folded scaffold, we have developed a cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form a target cyclic peptide. Theoretical analyses and NMR spectroscopy suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible in CHCl 3 . The optical properties including UV/Vis absorption, fluorescence, and circular dichroism (CD) were also evaluated. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups at the periphery of the cyclic skeleton. This α/ζ-alternating cyclic peptide is therefore expected to serve as a unique scaffold for arranging several functionalities., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Aiming at precisely arranging several proteinogenic α-amino acids on a folded scaffold, we have developed a cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form a target cyclic peptide. Theoretical analyses and NMR spectroscopy suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible in CHCl3. The optical properties including UV/Vis absorption, fluorescence, and circular dichroism (CD) were also evaluated. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups at the periphery of the cyclic skeleton. This α/ζ-alternating cyclic peptide is therefore expected to serve as a unique scaffold for arranging several functionalities. [ABSTRACT FROM AUTHOR]

The optically active cobalt(III) complex with chiral cyclen, (2S,5S,8S,11S)-2,5,8,11-tetraethyl-1,4,7,10-tetraazacyclododecane, preferentially binds to d-phenylglycine (D-Phg) or D-t-leucine (D-t-Leu) rather than L-Phg or L-t-Leu, respectively, with 20% de in dimethyl sulfoxide at 293 K. Comparative studies on the crystal structures of cobalt(III) complexes with D-Phg and L-Phg revealed that the diastereoselectivity is due to the difference in the steric hindrance that should occur between the amino group of Phg and the ethyl group of cyclen. [ABSTRACT FROM AUTHOR]

A water ‐ soluble cyclic hexapeptide comprising an alternate sequence of biphenyl ‐ cored ζ ‐ amino acids and proteinogenic α ‐ amino acids such as l ‐ leucine has been developed. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form the target cyclic peptide. Theoretical and NMR spectroscopic analyses suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups. More information can be found in the Full Paper by Mitsuhiko Shionoya et al. on page   1087 in Issue 10, 2017 (DOI: 10.1002/asia.201700203). [ABSTRACT FROM AUTHOR]

The article synthesizes a macrocyclic tetranuclear Ni(II) complex of an artificial β-dipeptide 1 which possesses two sets of tridendate ligands for in-line molecular arrangement. Researchers focused on biorelated molecular building blocks such as amino acids and nucleosides in constructing a more sophisticated molecular functions. They discovered that β-dipeptide 1 forms a cyclic trinuclear ZN(II) complex.

The article presents information on the β-turn structures of peptides. The turn structure can be constituted by four amino acid residues via hydrogen bonding between CO(i) and NH(i+3). A three-residue peptide fragment, Ac-Ala-Ala-Ala-NH2, can be folded into a turn3 through encapsulation by a porphyrin-assembled synthetic host. Despite the presence of only one intramolecular hydrogen bond, the turn conformation is very stable because of efficient host-guest interaction.

This article focuses on sequence-selective recognition of peptides. Although a few groups have reported artificial receptors for sequence-selective peptide recognition, the highly designed receptors are in their early stages. They are constructed by simply linking small recognition sites such as cyclodextrins, crown ethers, or amide groups, which all bind only a single amino acid residue. Having a large hydrophobic cavity, cage 1 binds as many as three amino acid residues. NMR and X-ray analyses reveal that the sequence-selective recognition is ascribed to cooperative multiple interactions between the residues and the cavity.

Review: [57 refs. [ABSTRACT FROM AUTHOR]