Rigidified 2-aminopyrimidines as histamine H4 receptor antagonists: Effects of substitution about the rigidifying ring

Abstract Three novel series of histamine H 4 receptor (H 4 R) antagonists containing the 2-aminopyrimidine motif are reported. The best of these compounds display good in vitro potency in both functional and binding assays. In addition, representative compounds are able to completely block itch responses when dosed ip in a mouse model of H 4 -agonist induced scratching, thus demonstrating their activities as H 4 R antagonists.