The subject invention provides anticoagulant compounds of formula I: ##STR00001## and pharmaceutically acceptable salts thereof, wherein R.sub.1, R.sub.3, n and Ar are as defined herein. The compounds of the subject invention can be used to treat at-risk populations thereby bringing relief of symptoms, improving the quality of life, preventing acute and long-term complications, reducing mortality and treating accompanying disorders. The invention further comprises pharmaceutical compositions comprising the compounds and salts of the invention, as well as methods of using the compounds, salts, and compositions of the invention.