Abstract
Several 3-substituted-2H-cyclohepta[b]furan-2-one derivatives were prepared and tested in vitro for positive inotropic character. Introduction of an isopropyl group at the 5-position of compound 8a caused an increase of PIC50 (negative logarithm of the dosage which increases the contractile force by 50%) from 4.48 to 5.10. Among the 5-isopropyl-8-alkoxy compounds, the isopropoxy compound 12f had the most potent activity with a PIC50 value of 5.99. Conversion of the ester group at the 3-position to a methylene group and of the alkoxy group at the 8-position to a substituted amino group caused a decrease in activity. The most active compound, 12f, was also found to have a weaker heart rate (HR)-increasing effect compared to milrinone and amrinone.
