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Strong Binding of Alkylguanidinium Ions by Molecular Tweezers: An Artificial Selective Arginine Receptor Molecule with a Biomimetic Recognition Pattern
Author(s) -
Schrader Thomas
Publication year - 1997
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/chem.19970030923
Subject(s) - hydrogen bond , chemistry , molecular tweezers , amide , moiety , stereochemistry , steric effects , molecular recognition , arginine , molecule , dipeptide , combinatorial chemistry , crystallography , amino acid , supramolecular chemistry , biochemistry , organic chemistry
Bisphosphonates 2 and 3 represent the first artificial receptor molecules for alkylguanidinium ions. They bind to the guanidinium moiety by forming a 1:1 chelate complex, stabilized by a planar network of electrostatic interactions and hydrogen bonds. This hydrogen bonding configuration is identical to the „arginine fork” postulated by Frankel as a key element in RNA–protein recognition of the AIDS virus. Our guanidinium–bisphosphonate complexes thus constitute the first synthetic model for this important biological interaction and demonstrate that the high binding energy can be a driving force for a conformational change in the receptor (induced fit, e.g., in the RNA). Although binding of monosubstituted alkylguanidines is generally strong ( K a ≈ 10 000 in DMSO), molecular tweezer 3 recognizes N ‐ and C ‐amide‐protected arginine derivatives especially well ( K a ≈ 300 000 in DMSO), because an additional hydrogen bond is formed between the amide and the phosphonate. Since 3 does not bind amines effectively, it is highly selective for arginine, even in the presence of lysine or other amino acids. For di‐, tri‐, and tetrasubstituted guanidines the association constant remains low ( K a ⩽1000 in DMSO) reflecting the increase in the steric bulk of the guest.