Total Synthesis of Ansellone G and Phorbadione.

The first total synthesis of marine sesterterpenoid ansellone G ( 2 ) was accomplished. This strategy utilizes the Prins cyclization reaction of a chloro-substituted homoallyl alcohol to synthesize the hydrobenzopyran skeleton. The preintroduction of the chloro groups facilitated the functional group transformation for 2 after constructing the carbon framework. Furthermore, we also successfully synthesized phorbadione ( 3 ) by dehydrating the tertiary alcohol. The HIV latency-reversing activity of the synthesized 2 , 3 , and deacetylated 2 was also evaluated.