[PAF-antagonists with phospholipid structure. 2. Phospholipids with heteroarene head groups and variations of the phosphorus-nitrogen distance; synthesis, characterization and structure-activity relationships].

A series of 27 PAF-analogues with heteroarene head groups and variation of the P-N-distance on the C-3-position of the backbone were synthesized, and the PAF-antagonistic activity on human blood platelets in vitro was evaluated. Investigation of structure-activity relationships revealed that PAF-antagonistic activity is strongly influenced by the 4-(Dimethylamino)-pyridine as polar head base and the distance between phosphate group and onium center. Maximal activity was observed with a chain length of 3 or 4 methylene groups. Among the compounds tested, 1-O-Hexadecyl-2-n-propylpropan-1,3-diol-3-phosphoric acid-4'-[4-(dimethylamino)pyridinium]butylester was the most effective inhibitor in the in vitro assay (KB = 0.3 mumol/l).