Synthesis and structural analysis of the active enantiomer of famoxadone, a potent inhibitor of cytochrome bc1.

Famoxadone is a newly commercialized fungicide and potent Qo-site inhibitor of cytochrome bc1. The S-(-)-enantiomer of famoxadone (the active component) was synthesized by two routes and was analyzed computationally and by X-ray crystallography. The molecule displays an extended conformation with flexibility in the structure imparted by the two terminal phenyl groups. In the crystal lattice, intermolecular hydrogen bonds occur between the NH and the oxygen atoms of the heterocycle.