主权项 |
1. A compound having the structure: wherein R1, R2, or R3 is -X-W-L-Z, wherein when R1 is -X-W-L-Z, X is NH, and R2 is —OH, and R3 is —H, when R2 is -X-W-L-Z, X is NH, R1 is —NH2, and R3 is —H, and when R3 is -X-W-L-Z, X is a heteroatom or lower alkyl group, R1 is —NH2, and R2 is —OH, and W is a lower alkyl group or a carbonyl group; L is a linker or at least one bond between W and Z; and Z is H, an alkyl group, a reactive functional group capable of reacting with a reactive partner to form a covalent bond, or a moiety of interest; or a salt thereof. |