Collect. Czech. Chem. Commun.
1989, 54, 2156-2170
https://doi.org/10.1135/cccc19892156
Conformation of 6-amino-6-deoxyhexonolactams
Karel Kefurta, Zdeňka Kefurtováa, Petr Trškab, Karel Bláhac, Ivo Fričc and Jiří Jarýa
a Laboratory of Monosaccharides, Prague Institute of Chemical Technology, 166 28 Prague 6
b Laboratory of Nuclear Magnetic Resonance, Prague Institute of Chemical Technology, 166 28 Prague 6
c Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6
Abstract
Eight configurational isomers of 6-amino-6-deoxyhexonolactam Ia-VIIIa and their tetra-O-acetyl derivatives Ib-VIIIb were studied using NMR and CD spectroscopy. For all the compounds most values of chemical shifts of the 1H and 13C nuclei as well as of vicinal coupling constants were obtained. Comparison of the observed values with 3J(H,H) values, calculated for various conformations of the studied compounds by a modified Karplus relationship, led to assignment of predominant conformation 1,NC4(D) or 4C1,N(D) to the lactams Ia-VIIIa and Ib-VIIIb in solution. For the measured set of compounds, the decisive conformation-determining requirement seems to be the equatorial position of substituent on the carbon next to the carbonyl group. The CD spectra of the lactams Ia-VIIIa in water, interpreted according to the currently used rules, in six cases agreed and in two cases disagreed, with the NMR results. The reasons of this discrepancy are discussed.
