irradiation of the steroidal N-iminopyridinium ylide 25, which can be obtained from 19-nortestosterone, leads quantitatively and in a regiospecific manner to the corresponding diazepine 26. In a second photochemical reaction 26 gives the cyclobutene derivative 27. Variable temperature 1H NMR and OCD measurements of the optically active diazepine 26 indicate that one of the two possible diastereoisomeric conformations
N-亚
氨基吡啶鎓的叶立德12和13容易经历区域特异性的光诱导的环扩展,分别形成同分异构的1,2-二氮杂pine 14和15。类似地,可以从19-
睾丸激素获得的甾族N-亚
氨基吡啶鎓叶立德25的紫外线辐射定量地且以区域特异性方式导致相应的二氮杂pine 26。在第二光
化学反应26中,得到
环丁烯衍
生物27。旋光性二氮杂pine的可变温度1 H NMR和OCD测量26 表示两个可能的非对映异构构象之一是优选的。