Total synthesis of the meso-triterpene polyether teurilene

The first total synthesis of the triterpene ether teurilene has been accomplished utilizing two vanadium-(V)-catalyzed oxidation-cyclization reactions with different stereoselectivities. The synthesis involved stereoselective and step-by-step construction of 2,5-cis- and 2,5-trans-tetrahydrofuran rings, vanadium (V)-catalyzed oxidation of 4-substituted 4-en-1-ol and subsequent cyclization of the resulting anti-epoxy alcohol, and a similar oxidation-cyclization of 5-substituted 4-en-1-ol by way of syn-epoxy alcohol. An improved synthesis of 1, which featured direct formation of bis(tetrahydrofuran) from squalene derivative by simultaneous double oxidation-cyclization, was also accomplished