Secoheliosphanes A and B and Secoheliospholane A, Three Diterpenoids with Unusual <i>seco</i>-Jatrophane and <i>seco</i>-Jatropholane Skeletons from <i>Euphorbia helioscopia</i>

Secoheliosphanes A (1) and B (2) and secoheliospholane A (3), possessing an unusual 7,8-seco-jatrophane skeleton and an unprecedented 9,10-seco-7,10-epoxyjatropholane skeleton, respectively, were isolated from the whole plants of Euphorbia helioscopia, along with two biogenetically precursors, a new jatrophane diterpene, 2-epi-euphornin I (4) and a known jatrophane diterpene, euphoscopin A (5). Structures of 1–4 including absolute configurations were elucidated on the basis of spectroscopic data, X-ray crystallography, and chemical conversion. Compounds 1 and 2 were prepared from 4 and 5, respectively, confirming their structural assignments. Notably, 1 and 2 presented the first examples of seco-jatrophane-type diterpenoids and 3 featured a novel 5/6/7/7-fused tetracyclic ring skeleton. Among them, compound 2 showed modest activity against HSV-1 with IC50 value of 6.41 μM.裂环续随子烷类（Secoheliosphanes）A（1）、裂环续随子烷类B（2）以及裂环续随子膦烷A（3，secoheliospholane A），分别具有罕见的7,8-裂环续随子烷（7,8-seco-jatrophane）骨架和前所未有的9,10-裂环-7,10-环氧续随子膦烷（9,10-seco-7,10-epoxyjatropholane）骨架，它们均从泽漆（Euphorbia helioscopia）的全株中分离得到；同时还获得了两个生源前体：一个新的续随子烷型二萜2-表-大戟灵I（2-epi-euphornin I，4）以及一个已知的续随子烷型二萜泽漆素A（euphoscopin A，5）。基于波谱学数据、X射线晶体衍射分析及化学转化方法，阐明了化合物1~4的结构（包括绝对构型）。研究人员分别以化合物4和5为原料合成了化合物1和2，验证了其结构解析结果。值得注意的是，化合物1和2为首例裂环续随子烷型二萜类化合物，而化合物3具有新颖的5/6/7/7稠合四环骨架。其中，化合物2对单纯疱疹病毒1型（HSV-1）表现出中等抑制活性，半数抑制浓度（IC50）为6.41 μM。