Multipoint recognition of catecholamines by hydrindacene-based receptors accompanied by the complexation-induced conformational switching.
The molecular recognition of catecholamines by hydrindacene-based receptors 1 and 2, as well as the durene-based receptor 3, and the guest-induced conformational changes are reported. These receptors selectively bind adrenaline and dopamine salts through the guests' ammonium group and 3-hydroxyl group on the aromatic ring. In the case of adrenaline, an additional hydrogen bond with a benzylic hydroxyl group is formed. In 2 % CD3CN/CDCl3, the association constants are of the order of 10(4) M(-1), which is much larger than with guests without the 3-hydroxyl groups (10(3) M(-1)). The two amide groups of receptor 1 can rotate freely around the C(aromatic)--C(amide) bond, whereas the tert-amide in 2 changes between two stable conformations at a slow enough rate to allow detection by (1)H NMR spectroscopy. In the absence of a guest molecule, the syn-conformer is less stable than the anti-conformer. On complex formation with adrenaline, the syn-conformer becomes dominant due to an intramolecular dipole-reversal effect in addition to multipoint hydrogen bonding.
Kawai
Hidetoshi
H
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. kawai@sci.hokudai.ac.jp
Katoono
Ryo
R
Fujiwara
Kenshu
K
Tsuji
Takashi
T
Suzuki
Takanori
T
D001665:Binding Sites; D002395:Catecholamines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004837:Epinephrine / Q000737:chemistry; D007192:Indenes / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
D002395:Catecholamines; D007192:Indenes; C488231:hydrindacene; D004837:Epinephrine