SYNTHESIS AND HISTAMINE H-2 AGONISTIC ACTIVITY OF ARPROMIDINE ANALOGS - REPLACEMENT OF THE PHENIRAMINE-LIKE MOIETY BY NONHETEROCYCLIC GROUPS

Analogues of the potent histamine H-2 agonist arpromidine, characterized by non-heterocyclic groups (phenyl, cyclo-hexyl, alkyl) instead of the pheniramine-like portion, were prepared and tested for their H-2 agonistic and H-1 antagonistic activity in the isolated guinea pig right atrium and ileum, respectively. In the diphenylpropylguanidine series an increase in H-2 agonistic potency resulted from mono- or difluorination at one or both phenyl rings in the meta and/or para position (pD2 less-than-or-equal-to 7.75 vs pD2 = 7.15 for the unsubstituted parent compound). Compounds chlorinated at both phenyl rings were considerably less potent. Highest combined H-2 agonistic/H-1 antagonistic potency was found in the 4-fluorophenyl series. The arpromidine analogue with cyclohexyl and methyl group instead of phenyl and pyridine ring proved to be 30 times more potent than histamine in the atrium. The H-1 antagonistic potency in cyclohexyl compounds was lower than in the diaryl series. Thus, aromatic rings appear not to be required for high H-2 agonistic potency but are useful for combined H-2 agonistic/H-1 antagonistic activity.