New Broad Spectrum Anthelmintic, Methyl 5(6)-Butyl-2-benzimidazolecarbamate

WE have found a series of anthelmintic compounds, one of the most potent of which is methyl 5(6)-butyl-2-benzimidazolecarbamate (II; SK and F 29044). Anthelmintic activity in this series of compounds was first found with thionocarbamate Ia. When a large number of compounds related to Ia were examined, it was found that 2-acyl-amino-benzimidazoles (Ib), 2-benzimidazolecarbamates (Ic) and 2-benzimidazolylureas (Id) also possess anthelmintic properties. In all cases, high activity was restricted to the lower members of the series in which the group R contained between one and three carbon atoms. The methyl carbamate derivative (Ic, R=OCH3), which seemed to be the most promising, was selected for further modification, and this led to the discovery of SK and F 29044 (II). Compound II is conveniently prepared by the reaction of 4-butyl-o-phenylene-diamine with carbomethoxycyanamide in boiling 2-propanol. It is a white crystalline solid which melts at 224°–227° C with decomposition.