Analogues of platelet activating factor (PAF). 1. Some modifications of the alkoxy chain.

Analogues of platelet activating factor (PAF) in which the ether oxygen has been removed (6) and in which the alkoxy chain at C1 has been replaced with a o-, p-, or m-alkylphenoxy group (30, 31, and 35, respectively) have been prepared. Compound 6 shows reduced platelet aggregation and hypotensive activity in comparison with C16 and C18 PAF. The results obtained for compounds 30, 31, and 35 indicate that the hypotensive and platelet aggregating responses are sensitive to structural modification of the ether chain. The ortho analogue 30 shows no platelet aggregating activity and only a weak hypotensive response. The para analogue 31 exhibits a moderate decrease in activity in both assays. The meta analogue 35 is the most active of the three.