Thioether phospholipids are a new class of synthetic phospholipid analogues exhibiting high level of activity in a wide spectrum of biological systems. l-4 Included among these are a series of antitumor active thioalkyl derivatives of platelet activating factor (PAF) lW3 that have been shown to exceed the tumor-cytotoxicity of the corresponding oxygen compounds. 3 Furthermore, sulfur substitution at the m-1 position appears to lower the platelet- ...