| abstract |
57 This invention provides compounds of the formulawhereinR<sub>1</sub>, R<sub>2</sub>, R<sub>3</sub>, R<sub>4</sub>, R<sub>5</sub>, and R<sub>6</sub> are independently hydrogen or C<sub>1</sub>-C<sub>4</sub> alkyl, or R<sub>6</sub> and one of R<sub>4</sub> and R<sub>5</sub> taken together form a bond; and acid addition salts thereof which are useful as inotropic agents. |