In one aspect, the invention relates to compounds having the formula: (I), wherein 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 the compounds; methods of using the compounds; and processes and intermediates for preparing the compounds.