@Article{IPB-2325, author = {Siener, T. and Holzgrabe, U. and Drosihn, S. and Brandt, W.}, title = {{Conformational and configurational behaviour of κ-agonistic 3,7-diazabicyclo[3.3.1]nonan-9-ones—synthesis, nuclear magnetic resonance studies and semiempirical PM3 calculations}}, year = {1999}, pages = {1827-1834}, journal = {J. Chem. Soc., Perkin Trans. 2}, doi = {10.1039/A806641H}, volume = {1999}, abstract = {2,4-Diaryl substituted 3,7-diazabicyclo[3.3.1]nonan-9-one 1,5-diesters were found to have a high affinity for κ-opioid receptors. To develop highly potent analgesics, the purpose of this study was the synthesis and the structural characterisation of the novel 2,4-bis(4-nitrophenyl), 2,4-bis(3-nitrophenyl), 2,4-bis(4-quinolyl), 2,4-bis(2-quinolyl), 2,4-bis(1-naphthyl) and 2,4-bis(2-naphthyl) substituted 3,7-diazabicyclo[3.3.1]nonan-9-one 1,5-diesters by means of NMR spectroscopy and molecular modelling. It could be proved that several derivatives undergo trans–cis-isomerisation of the aromatic rings linked to the rigid skeleton whereas others show rotational isomerisation. Semiempirical quantum-chemical PM3 calculations were performed to analyse the thermodynamic stability of the isomers as well as the mechanism of the trans–cis- or cis–trans-conversion.} }