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 1H and 13C nuclei as well as of vicinal coupling constants were obtained. Comparison of the observed 3J(H,H) with those calculated for various conformations by a modified Karplus relationship led to the assignment of predominant conformation 3H4(D) or 4H3(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.
使用NMR和CD光谱研究了5-
氨基-5-脱氧-D-戊糖内酯的四种构型异构体1a-4a及其三个O-乙酰衍
生物1b-4b。对于所有化合物,获得了1H和13C核的
化学位移以及邻位偶合常数。通过改进的Karplus关系计算各种构象的观察到的3J(H,H)与之比较,将主要构象3H4(D)或4H3(D)分配给溶液中的内酰胺1a-4a和1b-4b。确定构象的最重要因素似乎是位于羰基相邻碳上的取代基的伪赤道位置。在
水中解释的内酰胺1a-4a的CD光谱结果符合目前使用的规则,并与NMR结果一致。