Stereochemical studies of chiral h-1 antagonists of histamine: The resolution, chiral analysis, and biological evaluation of four antipodal pairs

The resolution of the H‐1 antihistamines chloropheniramine, dimethindene, carbinoxamine, and mebrophenhydramine is described. The optical purity of antipodal products is investigated by chiral HPLC (use of α1 ‐acid glycoprotein and β‐cyclodextrin columns) and NMR (spectra of β‐cyclodextrin inclusion complexes). Configurational relationships among the group are reviewed and assignments are confirmed and extended by circular dichroism evidence. Affinity constants of antipodal pairs for guinea pig ileum and cerebellum sites, determined by gut bath and binding experiments respectively, are reported together with some in vivo tests in man for central effects. Results are discussed in terms of configurational requirements for activity and variations in antipodal potency ratios within the group. © 1992 Wiley‐Liss, Inc.