Comparative structural study of histamine and its 4-substituted derivatives

• Published in: Journal of molecular structure. Theochem 1990, Vol.207 (3), p.157-167
• Main Authors: Smeyers, Yves G., Hernández-Laguna, A., Rández, J.J., Rández, F.J.
• Format: Article
• Language: English
• Subjects: Ab initio calculations; Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Physics
• ISSN: 0166-1280; 1872-7999
• DOI: 10.1016/0166-1280(90)85020-N

The geometries of histamine and a homologous series of 4-substituted agonists of H 2-receptors of histamine, in both the N3-H and N1-H tautomeric forms in their open trans-trans conformation, were fully optimized in the RHF STO-4G approximation. With this “optimal” geometry, the conformational-energy maps corresponding to the rotation about the C-C bonds in the ethyl-ammonium side chain were determined. The geometries and the conformation of the side chain are compared. It is seen that geometry does not depend on substitution. It was also found that the substitution does not affect significantly the conformational properties. The trans-trans conformation is verified to be a transition state in all the series considered. It is concluded that neither the geometry, nor the conformation, seems to be a determinant of the H 2-activity.