Structure elucidation and total synthesis of kulkenon.

The impressive biological profile of secondary metabolites isolated from strains of Sorangium cellulosum prompted us to initiate synthetic studies on kulkenon, also isolated from Sorangium cellulosum. The synthesis features a syn-selective vinylogous Kobayashi aldol reaction, recently developed by us, and a ring-closing intramolecular Heck reaction as the pivotal transformations. Comparison of the NMR spectra of the authentic and synthetic material revealed that the proposed configuration had to be revised. A combination of molecular modeling and NOE experiments was used to propose the revised configuration, which was confirmed by a new synthesis.