Chalcones of the root bark of Derris sericea

In addition to two chalcones and one flavanone previously isolated from the root bark of Derris sericea, a third chalcone, derricidin, has been found and its structure determined (III). Cyclization of this, and of the already known derricin (II), to the corresponding flavanones was accomplished. The almost, but not completely, identical fragmentation of such chalcone-flavanone pairs in the mass spectrometer is discussed and interpreted. NMR data, which contribute decisively to structure elucidation, are also presented.