Conformationally Restricted Analogs of Platelet‐Activating Factor (PAF)

The synthesis of the five‐membered cyclic phosphorodiamidic‐acid derivatives 10 and 11 as well as the preparation of the six‐membered cyclic phosphates 18, 19, 22–25 , and phosphoramidates 27–32 is described. The effects of these conformationally restricted platelet‐activating factor analogs on rabbit platelet aggregation are briefly discussed. The 2‐oxo‐1,3,2‐dioxaphosphorinanes 19, 25 , and 30 were found to be equally potent platelet‐activating factor antagonists as the known thiazolium salt 33 .