The anticoagulant activity of some selected warfarin analogues.

The anticoagulant activities of 6-, 7-, 8-, 4'-hydroxy, 6-chloro- and 6-bromowarfarin were determined in rabbits after intraperitoneal administration of 16.2 mumol kg-1 over 96 h. Substitution on the 4-hydroxycoumarin moiety resulted in reduction of the anticoagulant activity. 6-Chlorowarfarin was more potent than 6-bromowarfarin suggesting that the molecular size of 4-hydroxycoumarin moiety may be crucial for biological activity.