Experimental and Computational Investigation of the Oxime Bond Stereochemistry in c-Jun N-terminal Kinase 3 Inhibitors 11H-Indeno[1,2-b]quinoxalin-11-one Oxime and Tryptanthrin-6-oxime

11H-Indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) and tryptanthrin-6-oxime are potent c-Jun N-terminal kinase 3 (JNK-3) inhibitors demonstrating neuroprotective, anti-inflammatory anti-arthritic activity. However, the stereochemical configuration of carbon–nitrogen double bond (E- or Z-) in these compounds was so far unknown. In this contribution, we report results determination solid state by single crystal X-ray diffraction solution 1D 2D NMR techniques DFT calculations. It found that both solution, IQ-1 adopts E-configuration stabilized intermolecular hydrogen bonds, contrast to previously assumed Z-configuration could be only an intramolecular bond.