The present invention provides a compound of Formula (I) wherein R1, R2, R3 and R4 are independently H or C1-6 alkyl, provided that when R1, R2, and R3 are H, R4 is C1-6 alkyl, and when R1, R2, and R4 are H, R3 is C1-6 alkyl, and when R1, R3, and R4 are H, R2 is C1-6 alkyl, and when R2, R3, and R4 are H, R is C1-6 alkyl and pharmaceutical compositions comprising one or more said compounds, and methods for using said compounds for treating or preventing thromboses, embolisms, hypercoagulability or fibrotic changes.
