The present invention is concerned with novel deuterated Angiotensin-Converting Enzyme-2 (ACE-2) inhibitors of general structural formula I, their optically active enantiomers and diastereoisomers, and pharmaceutical salts and compositions thereof, as well as combination therapies which include compounds of the present invention, These compounds have high potency and selectivity for Angiotensin-Converting Enzyme-2 (ACE-2) inhibition, and are useful in the treatment of infectious respiratory diseases including the pandemic disease Covid-19, Severe Acute Respiratory Syndrome (SARS-CoV-2), Severe Acute Respiratory Syndrome (SARS-CoV), and other diseases caused by coronaviruses.