Scheme 1.

Schematic view depicting the strategy for the syntheses of CPP conjugates with the proapoptotic KLAK peptide. The CPP, without or with a Pra residue at the desired position, are assembled on a solid support by Fmoc strategy, the N-terminal residue being Ac-CysS-StBu. The galactose(s) moiety is introduced on the peptidyl-resin via click chemistry. Cleavage is performed on the solid support and followed by purification. The cysteine side chain is deprotected to conjugate the KLAK cargo, which contains an electrophilic cysteine (Cys-SNpys, Npys 3-nitropyridinesulfenyl). The CPP cargo conjugate is finally purified by HPLC