Building block, which can be used for conjugation with thiol groups. After removal of the Boc protecting group and conjugation with the mercaptane function the free methylamino side chain will open the maleimide ring under aqueous conditions. While the conjugation reaction between thiol and maleimid is reversible, it turns completely stable in the open ring structure. This becomes particularly important in the formation of conjugates with high value components, like in antibody-drug conjugation (ADC). Reference: Self-hydrolyzing maleimides improve the stability and pharmacological properties of antibody-drug conjugates; R.P. Lyon, J.R. Setter, T.D. Bovee, S.O. Doronia, J.H. Hunter, M.E. Anderson, C.L.Balasubramanian, S.M. Duniho, C.I. Leiske, F. Li, P.D. Senter; Nature Biotechnology. 2014; 32(10): 1059-1062. Doi:10.1038/nbt.2968.