5-Fluoro- and 8-fluorotrimetoquinol: selective .beta.2-adrenoceptor agonists

Abstract
The 5-fluoro and 8-fluoro analogues of trimetoquinol, TMQ, have been synthesized and evaluated for .beta.2- and .beta.1-adrenoceptor activity in guinea pig trachea and atria, respectively. The fluoro analogues of TMQ maintained potent .beta.2-adrenoceptor agonist activity but had reduced .beta.1-adrenoceptor agonist activity. The changes in .beta.1-activity of these compounds were correlated to differences in phenolic pKa''s. The .beta.1 and .beta.2-adrenoceptor actions of 2 and 3 were blocked in a competitive manner by propranolol. The enhanced .beta.2/.beta.1 selectivity for the analogues was found to be 8-fluoro analogue 3 > 5-fluoro analogue 2 < trimetoquinol (1).