Synthesis and antihistamine evaluations of novel loratadine analogues.

A series of loratadine analogues containing hydroxyl group and chiral center were synthesized. The effect of the synthesized compounds on the histamine-induced contractions of guinea-pig ileum muscles was studied. In addition, the in vivo asthma-relieving effect of the analogues in the histamine induced asthmatic reaction in guinea-pigs was determined. Most of the compounds exhibited definite H(1) antihistamine activity. The S-enantiomers, compounds 2, 4 and 8, are more potent than the R-enantiomers, compounds 1, 3 and 7. Compound 6 was the most active one among the eight synthesized compounds.