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）化合物A（1）、B（2）及裂环续随子烷醇A（3），分别拥有罕见的7,8-裂环续随子烷骨架与前所未有的9,10-裂环-7,10-环氧续随子烷醇骨架，二者从泽漆（Euphorbia helioscopia）的全株中被分离得到，同时伴随两种生物合成前体：1种新的续随子烷型二萜——2-表-大戟宁I（4），以及1种已知的续随子烷型二萜——续随子素A（euphoscopin A）。通过光谱数据分析、X射线晶体衍射及化学转化实验，阐明了化合物1至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，验证了其结构归属。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则拥有一种全新的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（Herpes Simplex Virus 1, HSV-1）表现出中等活性，半数抑制浓度（IC50）为6.41 μM。