Polystyrene styrene (PS) crosslinking resin is the earliest and most commonly used solid-phase carrier in peptide synthesis. Wang resin is the most widely used PS resin. Wang resin was originally designed for peptide synthesis of Fmoc strategy. The resin is made of chloromethyl polystyrene modified with p-hydroxyphenylethanol. Its structure is shown in the figure. Wang resin is an organic polymer. It is composed of small beads with a diameter of 20 ~ 150 μm. In order to make the carrier have a large grid space, which is enough to accommodate the growing long peptide chain and facilitate the reactants to enter the carrier, Wang resin with 1 ~ 2% cross-linking degree is generally used. The solid-state resin has good physical properties. Wang resin can be used to preload almost all ranges of Fmoc protected amino acids. However, if the cross-linking degree is too low, the swelling is too large, it is not easy to filter, and the mechanical properties are not good and easy to break.
Fig.1 The Structure of Wang Resin
The general peptide synthesis-Wang resin synthesis step is to swell the resin with DCM for 30 min, filter out the solvent for standby, and dissolve 2.5 mmol Fmoc amino acid and 2.5 mmol HOBT in 100 ml DCM, then add 2.5 mmol DIC and stir for 10 min. Add 1mmol of Wang resin and 0.1 mmol of DMAP that have been swelled in advance, seal the reaction vessel, control the temperature at 25-28 ℃ and react for 10-15 hours. After filtering off the reaction solution, wash it with DMF for 2-3 times. Add acetic anhydride: lpyridine = 1:1 for resin sealing reaction, seal the reaction vessel, control the temperature of 25-28 ℃, and react for 1 hour. Finally, DMF and methanol are added successively, washed and drained to obtain the resin.