Solid-State Strategy for the S-Conjugation of Peptides Catalyzed by Zeolites and Promoted by Microwave Radiation: A Green Approach

A green synthetic protocol to add a chemical function to a fully deprotected peptide to obtain a bioactive and/or fluorescent-labeled conjugate is reported. A range of S-conjugation reactions promoted by the commercially available LTA zeolite to introduce different substituents on peptide cysteine residues has been shown to take place in the solid state or in the presence of minimal amounts of organic solvent, with yields that are comparable to those of standard solution methods. The additional advantage of the procedure consists of easing the work up, for which green solvents, such as aqueous systems, can be employed. The protocol is implemented with microwave irradiation to shorten the reaction time as dielectric heating increases the diffusion rates of the mechanically milled reactants.