Patent ID: 7250413

Claim:
A compound having a structural formula I: or its pharmaceutically acceptable salt thereof, wherein, R 1 and R 2 independently are hydrogen, (C 1 -C 6 )alkyl, (C 1 -C 6 )alkenyl, (C 1 -C 6 )alkynyl, or R 1 and R 2 , together with the nitrogen atom to which they are attached, form a 4- to 8- membered heterocyclic ring containing zero or one additional nitrogen, oxygen, sulfur, or S(═O) 2 , wherein the carbon or nitrogen atoms of the ring are substituted with zero or one (C 1 -C 6 )alkyl, (C 1 -C 6 )alkylamino, di(C 1 -C 6 )alkylamino, (C 1 -C 6 )alkoxy, or R 1 is H and R 2 ; is L 25 -Q 25 , wherein L 25 is one of the structural groups: and wherein Q25 is one of the structural groups: