Synthesis and Structure−Activity Relationships of Conformationally Constrained Histamine H3 Receptor Agonists
摘要:
Immepip, a conformationally constrained analogue of the histamine congener imbutamine, shows high affinity and functional activity on the human H-3 receptor. Using histamine and its homologues as prototypes, other rigid analogues containing either a piperidine or pyrrolidine ring in the side chain were synthesized and tested for their activities at the human H-3 receptor and the closely related H-4 receptor. In the series of piperidine containing analogues, immepip was found to be the most potent H-3 receptor agonist, whereas its propylene analogue 13a was identified as a high-affinity neutral antagonist for the human H-3 receptor. Moreover, replacement of the piperidine ring of immepip by a pyrrolidine ring led to a pair of enantiomers that show a distinct stereoselectivity at the human H-3 and H-4 receptor.