Patent ID: 8501738

Claim:
A compound of Formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is —CH 3 , or —CH 2 CH 3 , wherein R 1 is optionally substituted with deuterium; R 2 is —CZ(R 3 ) 2 ; Z is —OH or —CH 3 , wherein the —CH 3 of Z is optionally substituted with deuterium; each R 3 is —CH 3 wherein each R 3 is optionally substituted with deuterium; each Y 1 is independently hydrogen or deuterium; and Y 2 is hydrogen or deuterium; with the proviso that when R 1 is unsubstituted —CH 3 or unsubstituted —CH 2 CH 3 Z is unsubstituted —CH 3 ; and R 2 is not substituted with deuterium; then at least one of Y 1 and Y 2 is deuterium.