PAF receptor. 2. Quantitative hydrophobic contribution of the agonist's etheroxid chain

In order to undertake a quantitative assessment of the contribution of the hydrophobic effect of the etheroxid chain to agonistic activity, it was necessary to include in the calculated data a highly lipophilic platelet-activating factor (PAF) analogue. The synthesis of such a compound--racemic 1-O-docosyl-2-O-acetylglycero-3-phosphocholine (C22 PAF)--is described. The regression analysis performed with data of 14 etheroxid analogues (reviewed by Godfroid et al., 1987), combined with data obtained with C22 PAF, is significant with respect to a parabolic evolution between lipophilicity of the chain and the logarithm of relative platelet stimulation. This result is characteristic of a hydrophobic interaction between the agonist and the PAF receptor.