Patent ID: 8729009

Claim:
A lysine compound represented by formula (Ia) or (Ib): wherein X is sulfur or selenium; —P 1 and —P 2 independently are (i) hydrogen, or (ii) an amine protecting group, —P 3 is (i) hydrogen; (ii) —X—R 6 , wherein —R 6 is an optionally substituted branched or straight chain, aliphatic or cyclic alkyl, heteroalkyl, alkenyl or heteroalkenyl group, and X is sulfur or selenium; (iii) a thiol or selenol protecting group; (iv) —R 5 or (v) —C(═O)—R 5′ ; wherein —R 5 and —C(═O)—R 5′ represent a residue of: (a) a covalently bonded peptide, lipid, carbohydrate, or polymer; or (b) a covalently bonded functional agent selected from the group consisting of a dye, a probe, a label, a tag, a solubility-modifying agent, an enzyme target, a receptor ligand, an immunomodulatory agent, a co-factor and a cross-linking agent; and —R 7 is (i) hydrogen, or (ii) an optionally substituted branched or straight chain, aliphatic or cyclic alkyl, heteroalkyl, alkenyl or heteroalkenyl moiety; or an ester, salt, solvate or hydrate of said lysine compound.