Discovery of Unusual Sesterterpenoids from Colquhounia coccinea var. mollis and Their Metabolic Implications.

Three unusual sesterterpenoids featuring unprecedented rearranged colquhounane (C 25 ) and tetranorcolquhounane (C 21 ) frameworks, colquhounoids E ( 1 ) and F ( 3 ) and norcolquhounoid F ( 2 ), were isolated from a Lamiaceae medicinal plant Colquhounia coccinea var. mollis . Their structures were elucidated by spectroscopic analysis and quantum chemical calculations. A biomimetic inspired regioselective cyclopropane cleavage was achieved under acidic conditions. The immunosuppressive activities of these new sesterterpenoids were also evaluated.