87892-68-0Relevant articles and documents
Organometallic β-turn mimetics. A structural and spectroscopic study of inter-strand hydrogen bonding in ferrocene and cobaltocenium conjugates of amino acids and dipeptides
Van Staveren, Dave R.,Weyhermueller, Thomas,Metzler-Nolte, Nils
, p. 210 - 220 (2003)
By using organometallic turn-mimetics, we have investigated the influence of a positive charge on the structure and stability of peptide turn structures which are stabilized by hydrogen bonds. Starting from metallocene mono- (1) or di-carboxylic acid (2), 11 amide derivatives were prepared, namely CpMC 5H4-CO-Phe-OMe (3), CpMC5H4-CO- AlaPhe-OMe (4), CpMC5H4-CO-NH-CH(CH3)-Ph (5), M(C5H4-CO-Phe-OMe)2 (6), M(C5H 4-CO-Ala-Phe-OMe)2 (7), and Fe(C5H 4-CO-NH-CH(CH3)-Ph)2 (8a) with Cp = η-C5H5 and M = Fe (ferrocene, a) or M = Co+ (cobaltocenium, b). All compounds were characterized by elemental analysis, MS, IR, electrochemistry, Moessbauer spectroscopy (a only) and NMR spectroscopy. Solid state structures of 4a, 6a, 7a, 3b, and 5b were determined by single crystal X-ray diffraction. 1H NMR data (δ(NH) and Δδ(NH) with T) as well as solution IR spectra were evaluated in order to determine intramolecular hydrogen bond interactions in solution. No intramolecular hydrogen bonds form in the monosubstituted derivatives 3-5 and in 8a. For 7, a strong intramolecular hydrogen bond is observed between the NHAla, and COAla. of the other ring, forming an 11-membered ring in solution as well as in the solid state. The situation is most complex for 6, which forms an intramolecular 8-membered ring by hydrogen bonds NHPhe ... COCp in the solid state (6a), but a symmetrical 11-membered ring structure with NHPhe ... CO Phe, bonds in solution. A comparison of the uncharged ferrocene derivatives with the iso-structural but positively charged cobaltocenium derivatives reveals only minor differences. Apparently, the presence of a positive charge does not significantly influence hydrogen bonds in peptide turn structures. Our results are related to geometries and amino acid sequences in protein turn structures and a nomenclature for turn mimetics with a parallel orientation of the two peptide strands is proposed. The Royal Society of Chemistry 2003.
Fragmentation-Rearrangement of Peptide Backbones Mediated by the Air Pollutant NO2.
Gamon, Luke F.,Nathanael, Joses G.,Taggert, Bethany I.,Henry, Fraser A.,Bogena, Jana,Wille, Uta
supporting information, p. 14924 - 14930 (2015/10/20)
The fragmentation-rearrangement of peptide backbones mediated by nitrogen dioxide, NO2., was explored using di-, tri-, and tetrapeptides 8-18 as model systems. The reaction, which is initiated through nonradical N-nitrosation of the peptide bond, shortens the peptide chain by the expulsion of one amino acid moiety with simultaneous fusion of the remaining molecular termini through formation of a new peptide bond. The relative rate of the fragmentation-rearrangement depends on the nature of the amino acids and decreases with increasing steric bulk at the α carbon in the order Gly>Ala>Val. Peptides that possessed consecutive aromatic side chains only gave products that resulted from nitrosation of the sterically less congested N-terminal amide. Such backbone fragmentation-rearrangement occurs under physiologically relevant conditions and could be an important reaction pathway for peptides, in which sections without readily oxidizable side chains are exposed to the air pollutant NO2.. In addition to NO2.-induced radical oxidation processes, this outcome shows that ionic reaction pathways, in particular nitrosation, should be factored in when assessing NO2. reactivity in biological systems.
Efficient synthesis of substituted oxopiperazines from amino acids
Mohamed, Nazim,Bhatt, Ulhas,Just, George
, p. 8213 - 8216 (2007/10/03)
The synthesis of substituted oxopiperazines, which may act as conformationally constrained peptide mimics, is reported. The synthesis is based on the cyclization of sulfonamide dipeptides with dibromoethane as the 1,2-dielectrophile. Alternatively, these
