Stereoselective synthesis of the bicyclic guanidine alkaloid (+)-monanchorin.

A new approach for the stereoselective synthesis of the bicyclic guanidine alkaloid (+)-monanchorin has been developed using a palladium(ii)-catalysed MOM-ether directed Overman rearrangement to establish the second stereogenic centre and a cross metathesis reaction to generate the carbon backbone. In the final stage, a one-pot acid mediated deprotection of aldehyde, guanidine and hydroxyl groups gave an intermediate that underwent facile cyclisation to (+)-monanchorin.