Synthesis and immunological activity of 5,6,6a,8,9,11a-hexahydronaphth[1',2':4,5]imidazo[2,1-b]thiazoles and 5,6,6a,9,10,11a-hexahydroanaphth[2',1':4,5]imidazo[2,1-b]thiazoles.

A series of 5,6,6a,8,9,11a-hexahydroanaphth[1',2':4,5]imidazo[2,q-b]thiazoles (17 and 20) and 5,6,6a,9,10,11a-hexahydronaphth[2',1':4,5]imidazo[2,1-b]thiazoles has been synthesized with cis- and/or trans-1,2-diamino-1,2,3,4-tetrahydronaphthalenes as the key intermediates and subsequently evaluated for immunological activity (effects on antibody formation and delayed-type hypersensitivity reaction). Among the compounds tested trans-5,6,6a,8,9,11a-hexahydronaphth[1',2':4,5]imidazo[2,1-b]thiazole (trans-17a) and (+/-)-5,6,6a beta,8,9,11a alpha-hexahydro-8 beta-hydroxy-9 beta-methyl-8 alpha-phenylnaphth[1',2':4,5]imidazo[2,1-b]thiazole (20a) showed the largest immunological activity in mice with a magnitude comparable to that of levamisole and were found to be considerably less toxic than levamisole in acute toxicological study. The structures of 18a and 20a were determined by X-ray crystallography.