1,3,6-Trisubstituted indoles as peptidoleukotriene antagonists: Benefits of a second, polar, pyrrole substituent

Article abstract of DOI:10.1021/jm00091a010

1,6-Substituted and 3,5-substituted indoles and indazoles containing acylamino and N-arylsulfonyl amide appendages are potent antagonists of the peptidoleukotrienes LTD₄ and LTE₄. A compound from the 3,5-substituted indole series, N-[4-[[5-[[(cyclopentyloxy)carbonyl]amino]-1-methylindol-3- yl]methyl]-3-methoxybenzoyl]-2-methyl-benzenesulfonamide (ICI 204,219), is undergoing clinical evaluation for asthma. Two new elements of structural diversity were introduced to this series of antagonists. An investigation of pyrrole substituents in the 1,6-substituted indoles demonstrated that substitution at C-2 was detrimental to biological activity, but the incorporation of hydrophilic groups at C-3 was beneficial. The introduction of a propionamide moiety at C-3 enhanced activity by 1 order of magnitude; N- [4-[[6-(cyclopentylacetamido)-3-[2-(N-methylcarbamoyl)ethyl]indol-1- yl]methyl]-3-methoxybenzoyl]benzenesulfonamide (15c) has a pK(B) of 10.7 at the LTD₄ receptor on guinea pig trachea. Modifications of the acylamino portion of the disubstituted antagonists demonstrated that a transposition of the amide CO and NH atoms was viable. N-Cyclopentylmethyl amides in both the 1,6- and 3,5-disubstituted indole series were 1 order of magnitude less potent than the corresponding cyclopentylacetamides. In both series this potency loss could be regained by the incorporation of a propionamide substituent at either C-3 or N-1, respectively. For example, N-[4-[[6-[N- (cyclopentylmethyl)carbamoyl]-3-[2-(pyrrolidin-1-ylcarbonyl)ethyl]indol-1- yl]methyl]-3-methoxybenzoyl]-2-methylbenzenesulfonamide (39c) has a pK(B) of 9.5.