Merck, 532304-5G, 2-Chlorotrityl chloride, polymer-bound

Application
Acid labile resin used in Fmoc-based solid phase peptide synthesis.
Mild acidic cleavage conditions lead to the release of the peptide acid where fully protected peptides can be released if desired.
2-Chlorotrityl chloride resins prevent racemization of the first amino acid and are thus very useful when racemic mixtures are forming (common with residues such as His or Cys).
This resin also prevents diketopiperazide formation, which can be an issue with proline C-terminal peptide sequences.

Use:
Attachment of the first amino acid residue is effected by stirring the resin, the protected amino acid, and excess diisopropylethylamine (DIEA) in dichloromethane.
Cleavage of the final protected peptide fragment is achieved under very mild conditions using either acetic acid/trifluoroethanol (TFE)/dichloromethane (1:1:8; v/v/v), hexafluoroisopropanol (HFIP)/dichloromethane (1:4; v/v) or simply 0.5% trifluoroacetic acid/dichloromethane (v/v).
Higher concentrations of TFA can be used if retention of peptide side chaing protecting groups is unimportant. Note that trityl chloride is moisture-sensitive, and, therefore, should be stored and handled appropriately.
If the resin becomes deactivated, treatment with acetyl chloride or SOCl₂ in toluene before use is recommended to restore its activity.