Practical Synthesis of α‐Amyrin, β‐Amyrin, and Lupeol: The Potential Natural Inhibitors of Human Oxidosqualene Cyclase

A practical synthesis of α‐amyrin (1), β‐amyrin (2), and lupeol (3) was accomplished in total yields of 32, 42, and 40% starting from easily available ursolic acid (4), oleanolic acid (5), and betulin (6), respectively. Remarkably, these three natural pentacyclic triterpenes exhibited potential inhibitory activity against human oxidosqualene cyclase. A practical synthesis of α‐amyrin (1), β‐amyrin (2), and lupeol (3) was accomplished in total yields of 32, 42, and 40% starting from easily available ursolic acid, oleanolic acid, and botulin, respectively. These three natural pentacyclic triterpenes exhibited potential inhibitory activity against human oxidosqualene cyclase.