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Porphyrin‐Based Peptide Receptors: Syntheses and NMR Analysis
Author(s) -
Sirish Mallena,
Chertkov Vyacheslav A.,
Schneider HansJörg
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020301)8:5<1181::aid-chem1181>3.0.co;2-u
Subject(s) - chemistry , porphyrin , two dimensional nuclear magnetic resonance spectroscopy , moiety , intramolecular force , proton nmr , crystallography , stereochemistry , protonation , amide , crown ether , heteronuclear single quantum coherence spectroscopy , ether , photochemistry , organic chemistry , ion
The synthesis and purification of a water‐soluble host compound that contains three pyridinium units and one spacer‐connected benzocrown ether unit in the meso ‐positions of porphyrin and of its Zn II or Cu II complexes is described. Metalation leads to small (compared to the apo ‐derivative) changes of selectivities with different peptides, with complexation constants in water of above 10 5 M −1 . One complex containing the tripeptide Gly‐Gly‐Phe is analyzed in detail by COSY, HSQC, HMBC, and NOESY NMR experiments. Temperature‐dependent spectra show activation energies for a intramolecular hydrogen exchange of amide protons with valence isomerization of the porphyrin ring, in accordance with the literature. Sharp signals for the spin system are only found at elevated temperature. Vicinal coupling constants within the crown ether moiety indicate stronger puckering than that reported for benzocrowns. All NMR signals of the complexed peptide are shielded, in particular those of the terminal phenylalanine unit, in line with its stacking on the porphyrin surface. A corresponding structural model, obtained by CHARMm simulation, is also in line with the observed intermolecular NOE cross peaks.