Magn Reson Chem 2011 May 14;49(5):205-12. Epub 2011 Mar 14.
Department of Chemistry, University of West Florida, Pensacola, FL, USA.
The geometries and relative energies of new N,N carbonyl dipyrrinone-derived oxime molecules (E/Z-s-cis 4a and E/Z-s-cis 4b) have been investigated. The calculated energies, molecular geometries, and (1) H/(13) C NMR chemical shifts agree with experimental data, and the results are presented herein. The E-s-cis conformations of 4a and 4b and the Z-s-cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti-orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments.