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Intramolecular Weak Interactions in the Thermodynamic Stereoselectivity of Copper(II) Complexes with Carnosine–Trehalose Conjugates
Author(s) -
Grasso Giuseppa I.,
Arena Giuseppe,
Bellia Francesco,
Maccarrone Giuseppe,
Parrinello Michele,
Pietropaolo Adriana,
Vecchio Graziella,
Rizzarelli Enrico
Publication year - 2011
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.201100313
Subject(s) - stereoselectivity , intramolecular force , carnosine , trehalose , copper , conjugate , chemistry , stereochemistry , organic chemistry , biochemistry , mathematical analysis , mathematics , catalysis
Abstract The interactions of metal ions with chiral molecules are of particular interest for relevant biochemical processes, as many of them are made possible only with a selected chirality of the stereocenters. In this work we report a study of the stereoselectivity of copper(II) complexes with D ‐trehalose– L ‐carnosine and D ‐trehalose– D ‐carnosine as a prototypical case of natural chirality selection. The interest in L ‐carnosine dipeptide is compounded by its antioxidant and antitumor properties, which are further enhanced when combined with D ‐trehalose. Potentiometric, calorimetric, and UV/circular dichroism (CD) spectroscopic measurements show that the copper(II) dimer of D ‐trehalose– L ‐carnosine is more stable than the D ‐trehalose– D ‐carnosine diastereoisomeric copper(II) dimer (log ${\beta {{{l}\hfill \atop 22- 2\hfill}}}$ −log ${\beta {{{d}\hfill \atop 22- 2\hfill}}}$ =3.6). Free‐energy calculations highlight that the cause of this different behavior lies with different intramolecular weak interactions between the diastereoisomers. The different pattern of hydrogen bonds and the different CH–π interactions between the π‐electron‐rich imidazole and the α‐glucose rings are more favorable by 5 kcal mol −1 in the L dimer.