​Wang Resin

Wang Resin
Wang resin is the standard peptide synthesis resin used with Fmoc-chemistry. The resin is acid
labile and finished peptides can be easily cleaved by treatment with 50 % (v/v) TFA/DCM. These
relatively mild cleavage conditions have made this resin popular also in solid phase organic
synthesis.
The first amino acid is attached to Wang resin using an activating agent such as
dicyclohexylcarbodiimide (DCC) and a catalytic amount of 4-dimethylamino-pyridine (DMAP).
These conditions can lead to partial epimerization of the amino acid, so HOBt is normally added to
reduce racemization. Even with HOBt added, racemization can be a problem if the first amino
acid is Cys or His. If DMF is used as the solvent in the coupling reaction, it should be degassed
under vacuum or sparged with nitrogen first to remove any dimethylamine that may be
contaminating it. The dimethylamine can remove the Fmoc group of the attached amino acid and
lead to C-terminal oligomeric impurities. After the first amino acid is attached, the resin should be
end-capped with acetic anhydride to block any unreacted active sites on the resin.