Patent ID: 7109190

Claim:
A compound having the chemical structure: or a salt thereof, wherein: n is 0 or 1, wherein: when n is 0: R 1 is hydrogen; A 1 is selected from the group consisting of oxygen and sulfur; R 2 does not exist; A 2 is carbon; A 3 and A 5 are independently selected from the group consisting of carbon and nitrogen such that the resulting ring is aromatic; and, R 3 is selected from the group consisting of hydrogen, —NH 2 and —CH 2 S(CH 2 ) 2 NH 2 ; when n is 1: A 1 is carbon; one or two of A 2 , A 3 , A 4 and A 5 is/are nitrogen, the rest are carbon; R 2 is —CH 2 S(CH 2 ) 2 NH 2 ; if A 2 is carbon, R 3 is hydrogen; if A 2 is nitrogen, R 3 does not exist; and, R 1 is selected from the group consisting of: hydrogen; —CH 3 ; —CH 2 CH 3 ; —CH 2 F; and, —CH 2 CH 2 F.