Peptide synthesis anchor groups used

A number of approaches may be adopted to achieve chemical synthesis of a peptide. The Merrifield solid phase synthesis method is perhaps the most widely used. This entails sequential addition of amino acids to a growing peptide chain anchored to the surface of modified polystyrene beads. The modified beads contain reactive chloromethyl (—CH2CI) groups. 

During solid phase synthesis peptides are bound to the solid support by means of the C-terminal carboxyl group. The properties of the anchor group positioned between the growing oligomer and the solid support are crucial for the success of a solid phase synthesis. Usually, specialised linkers are used which provide either peptide carboxylic acids or peptide carboxylic amides upon cleavage [4]. A cleavage mechanism that proceeds by a nucleophilic attack... 

A succinyl anchor is commonly cleaved by concentrated aqueous ammonia at ambient temperature for 1-2 h. It is possible to largely preserve the integrity of the succinyl linker and retain most of the N,P-deprotected oligonucleotide on the support by using ethanolamine deprotection [210]. The main problem with the succinate ester attached to the primary amino group on polymer is its propensity for base-catalyzed cycfization into the corresponding succinimide [211], similarly to the aspartimide formation in the Fmoc peptide synthesis. This unwanted side-reaction can be prevented by joining the succinate to the secondary amine, for... 

The oxime resin 5z [255,256], which forms an acid-stable anchor for the carboxyl group of amino acids, has been used for some time for the synthesis of C-terminal modified peptides and homodetic cyclic peptides. The key step in lactam formation is intramolecular nucleophilic attack of the A-terminus at the anchoring group. The resin also reacts with isocyanates and the products undergo nucleophilic attack by amines resulting in the release of ureas [257], Resin-bound Boc-tryptophan has been used in the acid-catalyzed Pictet-Spengler synthesis with final products cleaved as primary amides by... 

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