PAF receptor and “cache‐oreilles” effect. Simple PAF antagonists

Abstract
Nine simple and structurally flexible PAF antagonists were synthesized and their inhibitory effects on PAF induced platelet aggregation were measured. Compounds with PAF antagonistic activity exhibited a negative electrostatic potential generated by two trimethoxyphenyl groups (isocontour at −10 Kcal/mole) at various distances between the negative clouds. The optimal distance between the atoms generating the “cache-oreilles” system for exhibiting potent PAF antagonistic activity is estimated to be 11–13 Å. In the flexible molecules studied, the dispersion of the electronic distribution is not necessarily favorable for anti-PAF activity. The data support the simple bipolarized model for the PAF receptor that has been proposed by the authors.