This invention provides novel PF1270A substance, PF1270B substance and PF1270C substance represented by the following formula (1) or pharmaceutically acceptable salts thereof, a method for producing the same and a pharmaceutical composition which comprises at least one of the same as the active ingredient. Since a group of the PF1270 substances of the invention show high affinity for histamine H.sub.3 receptor, they are expected as novel histamine H.sub.3 receptor ligands useful as medicaments.