In one aspect, the invention relates to compounds having the formula: where R1-R6, a, b, Z, and X are as defined in the specification, or a pharmaceutically acceptable salt thereof. These compounds 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.在一個態樣中，本發明係關於具有下式之化合物：其中R1-R6、a、b、Z及X係如說明書中所定義，或其醫藥學上可接受之鹽。此等化合物具有腦啡肽酶抑制活性。在另一態樣中，本發明係關於包含該等化合物之醫藥組合物；使用該等化合物之方法；及用於製備該等化合物之方法及中間物。
