CONFORMATION OF 5-AMINO-5-DEOXYPENTONOLACTAMS

摘要

Four configuration isomers of 5-amino-5-deoxy-D-pentonolactam 1a-4a and their tri-O-acetyl derivatives 1b-4b were studied using NMR and CD spectroscopy. For all compounds chemical shifts of the H-1 and C-13 nuclei as well as of vicinal coupling constants were obtained. Comparison of the observed (3)J(H, H) with those calculated for various conformations by a modified Karplus relationship led to the assignment of predominant conformation H-3(4)(D) or H-4(3)(D) to the lactams 1a-4a and 1b-4b in solution. The most important factor for determining the conformation seems to be the pseudoequatorial position of the substituent on the carbon next to the carbonyl group. The results of the CD spectra of the lactams 1a-4a in water, interpreted according to the currently used rules, agreed with the NMR results. [References: 30]