Molecular structure and dynamics of the four 10-hydroxynortriptyline isomers

The three-dimensional structures, molecular conformations, and electrostatic potentials of the R-E-, S-E-, R-Z-, and S-Z-isomers of 10-hydroxynortriptyline were examined by computer graphics, molecular mechanical energy calculations, and molecular dynamics simulations in vacuo and in aqueous solution. Molecular models of the isomers, based on the structure of nortriptyline, were refined by energy minimization and used as starting points in the simulations. R-E- and S-Z-10-hydroxynortriptyline formed intramolecular hydrogen bonds between the side-chain nitrogen atom and the hydroxyl group during the simulations in vacuo, and had the side chain folded over the ring system in the minimum energy conformations. Intramolecular hydrogen bonding was not observed for R-Z- and S-E-10-hydroxynortriptyline, which had extended side chains in the minimum energy conformations and stronger negative molecular electrostatic potentials around the hydroxyl group than the R-E- and S-Z-isomers.