Synthesis of the common propellane core structure of the hasubanan alkaloids.

The racemic synthesis of the common propellane core structure found in various hasubanan alkaloids is reported. The successful completion hinged upon the stereocontrolled construction of the cis-substituted heterobicycle as a precursor for the intramolecular Dieckmann condensation. A novel strategy is introduced for the facile hydrolysis of a sterically demanding carboxamide under a mild condition. The 2-nitroanilide obtained by the Goldberg arylation of a carboxamide with 2-iodonitrobenzene was readily converted to the corresponding ester derivative by way of N-acylbenzotriazole. We expect that the reported synthetic route will allow the synthesis of a series of hasubanan alkaloids starting from the correspondingly functionalized 2-tetralone derivatives.