2-Chlorotrityl chloride resins, peptide synthesis

Chlorotrityl chloride resin is normally supphed with a displaceable chlorine content of 1.0-1.6 mmol/g. For the purposes of peptide synthesis, this substitution can sometimes be too high and can be reduced by treating the resin with a sub-stoichiometric amount of amino acid derivative and then capping imreacted sites with MeOH. 

To negate the need to use the harsh and potentially hazardous deprotection reagent hydrazine, a superior alternative, which is particularly compatible for use in Fmoc/rBu solid phase synthesis, is Af-Fmoc-hydroxylamine, which can be used to effect a nucleophilic displacement reaction of 2-chlorotrityl chloride resin (33) (Figure 9). The resultant N-Fmoc-aminooxy-2-chlorotrityl polystyrene resin can be used for the synthesis of peptide hydroxamates as described in Protocol 8. 

Synthesis of protected peptide fragments 2.2.1 Esterification of the first amino acid on 2-chlorotrityl chloride resin... 

---