Stereodynamics of some pyridoxine derivatives.
The conformational properties of three pyridoxine derivatives were studied by1H dynamic NMR spectroscopy. Conformational exchange caused by a rotation of 2-nytrophenyl group around one single C-C bond, of 2,4-dinitrophenyl substituent around two single C-O bonds, and twist-twist transformations of the seven-membered ketal cycle was observed by NMR experiments at low temperatures. Meanwhile, the conformational exchange of the acetal ring remains fast in the NMR timescale even at 198 K. The energy barriers for all observed conformational exchange processes were determined by the lineshape analysis of dynamic NMR spectra. The activation barriers of the 2-nitrophenyl group rotation were almost the same for all studied compounds, about 40-41 kJ/mol. The energy barriers of the conformational exchange processes of the 2,4-nitrophenyl group and the ketal cycle increased significantly up to 10 kJ/mol in comparison with previously studied compounds with similar structure. Copyright © 2016 John Wiley & Sons, Ltd.
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
I Z
IZ
Rakhmatullin
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
L F
LF
Galiullina
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
A A
AA
Balandina
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
M R
MR
Garipov
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
A D
AD
Strelnik
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
A S
AS
Galiullina
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
Y G
YG
Shtyrlin
Kazan (Volga Region) Federal University, 18 Kremlevskaya St., Kazan, 420008, Russia.
V V
VV
Klochkov
2D NOESY NMR; conformational exchange; dynamic 1H NMR; energy barrier; pyridoxine