New compounds active against resistant cattle ticks (Boophilus spp.): Relationship between structure and activity within the group of cyclic amidines

A series of cyclic amidines is described, many of which are highly active against resistant cattle ticks, Boophilus spp. The preferred compound is clenpyrin, 1-butyl-2-(3,4-dichlorphenylimino)pyrrolidine which paralyses the cattle ticks and inhibits their egg-production.