N1-Benzoyl-N2-[1-(1-naphthyl)ethyl]-trans-1,2-diaminocyclohexanes: Development of 4-chlorophenylcarboxamide (calhex 231) as a new calcium sensing receptor ligand demonstrating potent calcilytic activity

J Med Chem. 2006 Aug 24;49(17):5119-28. doi: 10.1021/jm051233+.


A structure-activity relationship (SAR) study was performed principally at the N1 position of N1-arylsulfonyl-N2-[1-(1-naphthyl)ethyl]-trans-1,2-diaminocyclohexanes, a new family of calcilytics acting at the calcium sensing receptor (CaSR). The most active compound in this series was the 4-(trifluoromethoxy)benzenesulfonyl derivative 7e, which displayed an IC50 of 5.4 +/- 0.5 microM with respect to the inhibition of calcium-induced tritiated inositol phosphate ([3H]IP) accumulation in Chinese hamster ovarian (CHO) cells expressing the CaSR. Replacement of the sulfonamide linkage of this compound by a carboxamide led to a 6-fold increase in activity (7m, IC50 = 0.9 +/- 0.2 microM). Among the carboxamides synthesized, one of the most active compounds was the 4-chlorophenylcarboxamide (1S,2S,1'R)-7n (Calhex 231, IC50 = 0.33 +/- 0.02 microM). The absolute configuration of (1S,2S,1'R)-7n was deduced from an X-ray crystallographic study of one of the diastereomers of compound 7d. The stereochemical preference for the (1S,2S,1'R)-isomers can be rationalized on the basis of a three-dimensional model of the calcilytic binding pocket of the CaSR. Removal of the C-1' methyl group or replacement of the 1-naphthyl group by a 2-naphthyl or biphenyl moiety led to appreciable loss of calcilytic activity. Compounds 7e, 7m, and Calhex 231 did not stimulate [3H]IP accumulation in CHO cells expressing or not expressing the CaSR.

MeSH terms

  • Animals
  • Benzamides / chemical synthesis
  • Benzamides / chemistry
  • Benzamides / pharmacology*
  • CHO Cells
  • Cricetinae
  • Crystallography, X-Ray
  • Cyclohexylamines / chemical synthesis
  • Cyclohexylamines / chemistry
  • Cyclohexylamines / pharmacology*
  • Inositol Phosphates / antagonists & inhibitors
  • Inositol Phosphates / metabolism
  • Ligands
  • Models, Molecular
  • Molecular Structure
  • Protein Conformation
  • Rats
  • Receptors, Calcium-Sensing / biosynthesis
  • Receptors, Calcium-Sensing / drug effects*
  • Receptors, Calcium-Sensing / genetics
  • Stereoisomerism
  • Structure-Activity Relationship


  • Benzamides
  • Cyclohexylamines
  • Inositol Phosphates
  • Ligands
  • N(1)-(4-chlorobenzoyl)-N(2)-(1-(1-naphthyl)ethyl)-1,2-diaminocyclohexane
  • Receptors, Calcium-Sensing