Two new isoquinolone alkaloids, noroxyhydrastinine (I) and thalifoline (II) have been obtained from T. minus L. var. adiantifolium Hort. Characterization by physical methods and chemical synthesis have shown the former to be 6,7-methylenedioxy-1-oxo-1,2,3,4-tetrahydroisoquinoline and the latter to be 2-methyl-6-methoxy-7-hydroxy-1-oxo-1,2,3,4-tetrahydroisoquinoline. © 1969.