In one aspect, the invention relates to compounds having the formula: where R1, R2, R3, R7, R8, Z, X, b, and c are as defined in the specification, or a pharmaceutically acceptable salt thereof. These compounds are nitric oxide donors and have neprilysin inhibition activity. In another aspect, the invention relates to pharmaceutical compositions comprising such compounds; methods of using such compounds; and processes and intermediates for preparing such compounds.