Cardenolides and diterpenes as a source of and model for positive ionotropic agents.

Taking the natural cardenolides as a model for new inotropic agents, pimaranic, cyclohexanic and hydroindenic derivatives have been synthesized and tested. Several of these derivatives are positive inotropics and two of the D3a-unsaturated bis(amidinohydrazono)hydroinenes also are selective Na+, K+-ATPase inhibitors.