Pyrrolidine melanocortin-specific compounds

A compound having the structure:

• 58
• or a stereoisomer or pharmaceutically acceptable salt thereof,
• wherein
• R1 is -L1-J;
• R2 is selected from the group consisting of —(C═O)—W and —(C═O)—NH—(CH2)y—W;
• R3 is -L2-Q;
• L1 is a linker selected from the group consisting of —(CH2)y—, —O—(CH2)y—, —O—, —NH—(CH2)y—, —(C═O)(CH2)y—, —(C═O)—O—(CH2)y—, —CH2(C═O)NH—, and —(C═O)—NH—(CH2)y—;
• J is a ring structure selected from the group consisting of substituted or unsubstituted aromatic carbocyclic rings, substituted or unsubstituted non-aromatic carbocyclic rings, substituted or unsubstituted aromatic fused carbobicyclic ring groups, substituted or unsubstituted aromatic carbocyclic ring groups wherein the rings are joined by a bond or —O—, and substituted or unsubstituted aromatic fused heterobicyclic ring groups;
• wherein in each instance the rings comprise 5 or 6 ring atoms;
• W is a heteroatom unit with at least one cationic center, hydrogen bond donor or hydrogen bond acceptor wherein at least one atom is N;
• L2 is a linker selected from the group consisting of
• 59
• Q is an aromatic carbocyclic ring selected from the group consisting of phenyl, substituted phenyl, naphthyl and substituted naphthyl;
• R4 is —R5 or —R5—R6;
• R5 is from one to three amino acid residues or an amine capping group, provided that if R6 is present, R5 is at least one amino acid residue;
• R6 is H or an amine capping group;
• and
• y is at each occurrence independently from 0 to 6;
• wherein the carbon atoms marked with an asterisk can have any stereochemical configuration.