1-[8-(2-chlorophenyl)-9-(4-chlorophenyl)purin-6-yl]-4-ethylaminopiperidine-4-carboxamide 1-[8-(2-chlorophenyl)-9-(4-chlorophenyl)purin-6-yl]-4-ethylamino-piperidine-4-carboxamide 1-[8-(2-chlorophenyl)-9-(4-chlorophenyl)-6-purinyl]-4-ethylamino-4-piperidinecarboxamide 1-[8-(2-chlorophenyl)-9-(4-chlorophenyl)purin-6-yl]-4-ethylamino-isonipecotamide