PEG-polystyrene resins consist of a low crosslinked polystyrene matrix on which polyethylene glycol is grafted. The PEG spacer is attached via an ethyl ether group which increases stability towards acid treatment and minimizes PEG-leaching. These resins show modified physico chemical properties which are highly dominated by the PEG moiety. The PEG spacer is in the range of MW 3000 Da. Residues which are sensitive to racemisation during esterification reactions like His and Cys can be attached to the resin without racemisation. Due to the bulkiness of the trityl group, diketopiperazine formation is suppressed which makes this linker ideal for peptides with C-terminal Pro. This resin is recommended for synthesis of peptides up to 40 residues in length. The sensitivity towards TFA is comparable to the 2-Chlorotrityl linker. Cleavage can be achieved with 50% AcOH in CH₂Cl₂ to liberate protected peptides. For free peptides 95% TFA is afforded.
