Acetyl glyceryl ether phosphorylcholines (platelet-activating factors ; PAFs), their enantiomers, and their analogues were efficiently synthesized in a stereochemically unambiguous manner starting from D-and L-tartaric acids as chiral synthons. The enantiomer of C16-PAF (S-comfiguration) showed far less activity than the natural PAF (R-configuration), and the N-methylpiperidine and N-methylpyrrolidine analogues were found to possess much higher activity than natural C16-PAF.