Canataxpropellane, a novel taxane with a unique polycyclic carbon skeleton (tricyclotaxane) from the needles of Taxus canadensis

A novel taxane with an unprecedented 5/5/4/6/6/6-membered hexacyclic skeleton containing [3.3.2]propellane was isolated from the needles of the Canadian yew, Taxus canadensis. The structure was established as 2α,10β-diacetoxy-5α,9α,20α-trihydroxy-3α,11α;4α,12α;14α,20-tricyclotaxan-13-one (1), which exists as two conformational isomers on the basis of spectroscopic analysis. This compound would be biogenetically derived from a normal 6/8/6-taxane by the intramolecular aldol reaction and [2+2] cycloaddition.