IUCr journals

The zwitterion (23'E)-(23R,25S)-23-[1-(oxidoiminio)ethyl]-5β-spirostan-3β-yl acetate

Acta Cryst. (2009). E65, o2954-o2955 (doi.org/10.1107/S1600536809044651)

[Zwitterionic oxime group] The structure of the zwitterionic oxime group as observed in the solid state by XRD.
Steroids are responsible for important biological functions in living beings. Any modification in their skeleton, functional groups, or stereochemistry may alter dramatically their biological activity. When working on the oximation of a sarsasapogenin derivative, we were aware of a non-conventional behavior of the product in acid media. Single-crystal XRD data revealed that the oxime group is indeed found in the rather rare zwitterionic form, as a consequence of the transfer of a proton from the O atom to the N atom.
M.-G. Hernández Linares, J. Sandoval Ramírez, S. Meza Reyes, S. Montiel Smith and S. Bernès