abstract |
A compound of Formula 1: ** (See formula) ** wherein: R1 is H, ** (See formula) ** or CH2NHC (O) (CH2) mCO2H; R2 is H, ** (See formula) ** or CH2NHC (O) (CH2) mCO2H; R3 is H; provided that either R1 or R2 are H, and provided that both R1 and R2 and are not H simultaneously; m is 1, 2, 3, 4, or 5; and n is 1, 2, 3, 4, or 5. |