Structure of the isonicotinyl hydrazone of norethindrone

The contraceptive steroid norethindrone reacts with isoniazid both in vivo and in vitro to give the corresponding hydrazone, which exists as syn and anti (with respect to C-4) isomers. These isomers rapidly interconvert, with the anti form predominating in solution. The identification of the isomers was based on an interpretation of 1H- and 13C-NMR spectroscopic data and corroborated by high-performance liquid chromatographic UV spectrophotometric evidence. 1H- and 13C-NMR spectroscopic data for other derivatives of norethindrone hydrazone are presented and interpreted.