Is samoquasine A indeed benzo[f]phthalazin-4(3H)-one?: Unambiguous, straightforward synthesis of benzo[f]phthalazin-4(3H)-one and its regioisomer benzo[f]phthalazin-1 (2H)-one

In search for the structural elucidation of samoquasine A, a natural product isolated from the seeds of Annona squamosa L., two benzo [f] phthalazinone isomers have been synthesized. The synthetic pathway followed to build up these skeletons is based on the combination of two Suzuki reactions on a pyridazinone precursor and a ring closure reaction via a condensation reaction. H-1 NMR data of the synthesized compound allowed to establish that the structure of the natural product samoquasine A is not benzo [f]phthalazin-4(3 H) -one, as previously suggested. (C) 2007 Elsevier Ltd. All rights reserved.