The crystal and molecular structure of tomatidine hydrobromide and its relation to the steroidal bromosapogenins

Abstract

The complete structure of the steroid alkaloid tomatidine was determined from a three-dimensional X-ray diffraction analysis of the hydrobromide. The crystals are orthorhombic, P2₁2₁2₁ with four molecules in a cell of dimensions: a= 14·07, b= 7·37, c= 24·7 Å. The structure was solved by a peak-searching techinque (FATAL). The relative orientations of the oxygen and nitrogen about the spiro-carbon atom, and that of the methyl group relative to ring F, were established. Refinement was terminated at R= 10·7% for the 1420 observed terms. The relation between the structure of the alkaloid and that of the steroidal sapogenis of the tigogenin series is discussed.