Conospermum teretifolium

Conocurvone la is a deoxy-trimer of tereti-folion B (2a), a compound that has been known for longer and was first isolated from Conospermum teretifolium. The fast atom bombardment (FAB) mass spectrum of the tri-meric quinone revealed a molecular ion corresponding to the formula CeoHseOn, but the structure of la was in the end only fully elucidated by synthesis. The reason for this was that atropoisomeric equilibria were formed and led to more or less complex H-NMR spectra that varied with solvent and with temperature. The compound therefore appeared to be a complex mixture. However, the synthetic product was identical to the natural material, even in its chiroptical parameters, thus confirming the structure and also the low rotation barrier around the quinone-quinone axis, a property which has also been found for other quinonoid-quinonoid-coupled oligomers. 

---