Studies on 2-Benzimidazolethiol Derivatives. V : Structure-Activity Relationship on Analgesic Action of 1-(Dialkylaminoalkyl)-2-(p-ethoxyphenylthio)benzimidazole

1-(2-Diethylaminoethyl)-2-(p-ethoxyphenylthio)benzimidazole (I) is considered to be a morphine-like analgesic and its derivatives, 1-(diethylaminoalkyl)-2-(p-ethoxyphenylthio) benzimidazoles, were synthesized to test their analgesic effect by the pressure method. Except for the 1-(2-pyrrolidinoethyl)derivative showing better activities than I or morphine, other derivatives did not show much effect, such as 1-diethylaminomethyl, 3-diethylaminopropyl, 1-[2-(allylamino)ethyl], 1-(2-dialkylaminopropyl), and 1-(1-methyl-2-piperidinoethyl) derivatives. The allyl derivative did not show any antagonistic action against I or morphine. Some discussions were made on the central atom, basic nitrogen, and the flat aromatic portion in the molecules of I and its analogs.