Synthesis of Thalprzewalskiinone, a Revision of Structure

A direct comparison of the spectral data for synthetic 2-methyl-6,7-dimethoxy-3 ' -methoxy-4 ' -hydroxy-oxobenzylisoquinoline iodide (1) and its positional isomer 2-methyl-6,7-dimethoxy-3 ' -hydroxy-4 ' -methoxyoxobenzylisoquinoline iodide (2) with the data obtained for the oxobenzylisoquinoline alkaloid thalprzewalskiinone revealed that the original structural assignment of the alkaloid as 1 was in error. These results mandate the revision of structure of thalprzewalskiinone to 2-methyl-6,7-dimethoxy-3 ' -hydroxy-4 ' -methoxyoxobenzylisoquinoline quinoline iodide (2).