2, 4-pyrimidinediamines (11) and the related W-1H-benz-imidazol-2-yl-5, 6, 7, 8-tetrahydro- N4-phenyl-2, 4-quinazolinediamines (111). Compounds I1 and I11 could conceivably be formed by a dehydrogenation in vivo of I, resulting in ring closure of the unsubstituted nitrogen of the guanidine moiety on to the ortho position of the phenyl ring. In addition, the antifilarial activity of the benzimidazole anthelmintic mebenda~ ole~-~(IV) also encour-
