| Abstract
| - A group of five highly functionalized polycyclicα,γ-disubstituted-α,β-unsaturated-γ-lactones(3−7) featuring a unique bicyclo [11.1.0] carbon skeletonjoined in a trans fashion have been isolatedfrom a Caribbean gorgonian, Pseudopterogorgia bipinnata.These rare marine diterpenoids canbe regarded as representatives of the uncommon gersolane ring system.Two of the new metabolites,pinnatin A (3) and pinnatin B (4), showedsignificant differential antitumor activity in theNationalCancer Institute's 60-cell-line tumor panel. The biogenesis ofthe pivotal metabolite pinnatin A(3) appears to involve a photochemically allowed[σ2a + π2a]cycloaddition process of a conjugated2,5-bridged furanocembrane precursor. Structural assignments wereaccomplished throughextensive spectroscopic analysis including 2D NMR, accurate massmeasurements (HREIMS), X-raycrystallography, and chemical interconversions.
|
