Patent ID: 7332571

Claim:
A compound having the structure of Formula (XI): wherein: A is phenylene; B is a bond; R 1 is H, an amino protecting group, or at least one amino acid; R 2 is OH, an ester protecting group, or at least one amino acid; R is alkyl; each of R 3 and R 4 is H; R 5 L-X, where X is selected from the group consisting of a polyalkylene glycol or a detectable label, wherein the detectable label is selected from a fluorescent, phosphorescent, chemiluminescent, chelating, intercalating, radioactive, and chromophoric moiety; and any combination of the above; and L is optional, and when present is a linker selected from the group consisting of alkylene, substituted alkylene, alkenylene, substituted alkenylene, —O-(alkylene or substituted alkylene)-, —S-(alkylene or substituted alkylene)-, —S(O) k (alkylene or substituted alkylene)-, —C(O)—, —C(O)-(alkylene or substituted alkylene)-, —C(S)—, —C(S)-(alkylene or substituted alkylene)-, —NR′-(alkylene or substituted alkylene)-, —C (O)N(R′)—, —CON(R′)-(alkylene or substituted alkylene)-, —CSN(R′)-, —CSN(R′)-(alkylene or substituted alkylene)-, —N(R′)CO-(alkylene or substituted alkylene)-, -(alkylene or substituted alkylene)-O—N═CR′—-, -(alkylene or substituted alkylene)-C(O)NR′-(alkylene or substituted alkylene)-, -(alkylene or substituted alkylene)-S(O) k -(alkylene or substituted alkylene)-S—, -( alkylene or substituted alkylene)-S—S—, —C(R′)═N—, —C(R′)═N—N(R′)—, —C(R′)═N—N═, —C(R′) 2 —N═N—, and —C(R′) 2 —N(R′)—N(R′)—, where each R′ is independently H, alkyl, or substituted alkyl; or a salt thereof.