A proposed common spatial pharmacophore and the corresponding active conformations of some peptide leukotriene receptor antagonists.

Molecular modeling studies were carried out by a combined use of conformational analysis and 3D-QSAR methods of identify molecular features common to a series of hydroxyacetophenone (HAP) and non-hydroxyacetophenone (non-HAP) peptide leukotriene (pLT) receptor antagonists. In attempts to develop a ligand-binding model for the pLT receptor, the Apex-3D program was used to identify biophoric structural patterns that are common to 13 diverse sets of compounds showing different levels of biological activity. A systematic conformational analysis was carried out to obtain sterically accessible conformations for these flexible compounds. Apex-3D was then utilized to propose common biophoric regions based on the selection of one of several conformations (MOPAC-minimized AM1) from each compound's data set that best fits the biophoric pattern and the resulting superimposition with all the other data-set compounds. Apex-3D identified three common biophoric features important for activity: one as the hydroxyl, acetyl, carbonyl and carboxyl groups, which mimic the acid-binding region of an agonist, the other as the hydrogen-bond donating site, and the third part is represented by a plane in which lipophilic aromatic groups align. The structure-activity relationships were then assessed by using the 3D-QSAR model. A common biophore model is proposed from the Apex-3D analysis which may be useful in designing new pLT antagonists. Molecular volumes and electrostatic potential similarities were also calculated in order to obtain the important structural requirements for the activity.