
%0 Journal Article
%A Rae, ID 
%A Rae, ID 
%A Simmonds, PM 
%A Simmonds, PM 
%T The Structure of Papaverine in Solution as Determined by <sup>1</sup>H Nuclear Magnetic Relaxation Methods
%J Australian Journal of Chemistry
%D 1987/05/01
%V 40
%N 5
%P 915-923
%K 
%R https://doi.org/10.1071/CH9870915
%U https://www.publish.csiro.au/paper/CH9870915 
%X Hydrogen relaxation in the papaverine molecule in CDCl3 solution has been studied so as to derive the conformation about the C1-CH2 bond. This was done for papaverine itself, in which the resonances of H5 and H8 were reassigned on the basis of NOESY spectra, and in the 7-OC2H3 analogue, the spectrum of which confirms the reassignment. The value for the torsional angle C 8a-C1-CH2-C lays between 70 and 92º, in good agreement with those found in crystals of papaverine , its hydrochloride, and the related alkaloid isosevanine (all in the range 68-94º). Conformational energy calculations show a broad energy minimum over the range 60-70º. The 6,7-methylenedioxy analogue of papaverine has essentially the same conformation but tumbles more rapidly in solution, the Tc value for it being 1.9&#215;10-1ls whereas values for papaverine were 5.6&#215;10-11 s (from 1H relaxation) and 3.1&#215;1011 s (from 13C relaxation). 
