(Z), Not (E) - An End to a Century of Confusion about the Double-Bond Stereoisomers of 3-Amino-2-cyanoacrylates

Potent and selective myosin inhibitors are of vast scientific interest in the development of treatments for diseases involving myosin dysfunction or overactivity. A novel fungicide, ethyl 2-cyano-3-amino-3-phenylacrylate (commercialized as phenamacril), was recently identified as an inhibitor of myosin-5 in F. graminearum. Although the compound has been known since 1900, a general confusion concerning the stereochemical configuration at the exocyclic double bond persists in the literature, thus restricting further drug development of this compound and derivatives. By using NMR and quantum mechanical calculations, this work establishes the stereoconfiguration as the (Z) form and that the effect of a single hydrogen bond is crucial in keeping these types of molecules in a single configuration.