Analogs and conjugates of beta-aminoisobutyric acid (baib)

A compound having the structural formula:

• or a salt thereof, and/or solvate or hydrate thereof, wherein:
• A is —OH and B is —C(O)R1;
• A is —NR2R3 and B is H;
• A is —OH and B is fluorenylmethyloxycarbonyl;
• A is —OH and B is —(C5-alkyl)-NR4R5;
• or
• A is
• and B is H;
• wherein
• R1 is —(C1-C2-alkyl)-SR6;
• R2 and R4 are H;
• R3 is —(C1-C2-alkyl)-SR7;
• R5 is —(C3-alkyl)-C(O)OH;
• wherein
• R6 is H or
• R7 is H, —(C1-alkyl)-C(O)NHR9, or
• wherein
• R8 and R10 are a —(C1-alkyl)-D
• R9 is a —(C4-alkyl)-E;
• and
• wherein
• D and E are a label or a protein.