Facile Preparation of Bioactive <i>seco</i>-Guaianolides and Guaianolides from <i>Artemisia gorgonum</i> and Evaluation of Their Phytotoxicity

Commercially available santonin was used to synthesize seven sesquiterpene lactones using a facile strategy that involved a high-yielding photochemical reaction. Three natural products from Artemisia gorgonum were synthesized in good yields, and in the case of two compounds, absolute configurations were determined from X-ray quality crystals. The structures previously reported for these compounds were revised. Sesquiterpene lactones were tested using the etiolated wheat coleoptile bioassay, and the most active compounds were assayed in standard target species. seco-Guaianolide (4) showed higher phytotoxic activities than the known herbicide Logran. This high activity could be due to the presence of a cyclopentenedione ring. These results suggest that compound 4 should be involved in defense of A. gorgorum, displaying a wide range of activities that allow proposing them as new leads for development of a natural herbicide model with a seco-guaianolide skeleton.以市售山道年（santonin）为原料，通过包含高产率光化学反应的简便合成策略，成功制备7种倍半萜内酯（sesquiterpene lactones）。从戈贡蒿（Artemisia gorgonum）中分离得到的3种天然产物均以良好收率完成全合成；其中2种化合物的绝对构型通过X射线衍射级晶体得以确定，此前针对这些化合物所报道的分子结构均得到了修正。采用黄化小麦胚芽鞘生物测定法对所合成的倍半萜内酯进行活性初筛，并选取活性最强的化合物在标准受试物种中开展进一步活性验证。编号为4的开环桉叶烷内酯（seco-Guaianolide）的植物毒性活性优于市售除草剂Logran，该优异活性可能与其分子中含有的环戊烯二酮环（cyclopentenedione ring）有关。上述研究结果表明，化合物4可能参与戈贡蒿（A. gorgorum）的防御机制；该类化合物具有广谱的生物活性，有望作为开发具有开环桉叶烷内酯骨架的天然除草剂模型的全新先导化合物。