Synthesis and structure–activity relationship of tricyclic carboxylic acids as novel anti-histamines

A series of tricyclic carboxylic acids having 6-amino-pyrimidine-2,4(1H,3H)-dione with piperazino or homopiperazino moiety linked by propylene, were synthesized and evaluated for their affinity toward human histamine H1 receptor and Caco-2 cell permeability. Selected compounds were further evaluated for their oral anti-histaminic activity in mice, bioavailability in rats, and their anti-inflammatory activity in mice OVA-induced biphasic cutaneous reaction model. Among the compounds tested, dibenzoxazepine carboxylic acid 13b showed both histamine H1 receptor antagonistic activity and anti-inflammatory activity in vivo. In addition, 13b exhibited low affinity toward α1 receptor and low occupancy of H1 receptor in the brain. It is therefore, believed that 13b is a potential candidate for development as 3rd generation anti-histamine.

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