4.2.1.125 | dammarenediol II = (3S)-2,3-epoxy-2,3-dihydrosqualene + H2O |
an unusually complex and flexible reaction mechanism generates this ring system. As a general mechanism, firstly (3S)-2,3-oxidosqualene adopts a preorganized chair-chair-chair conformation, and activated by cationic attack. Then the oxirane ring of (3S)-2,3-oxidosqualene opens, following with a cascade of cation-olefin cyclizations, and generates a cyclic C-20 dammarenyl cation |
748118 |