Show the generic chemical structure of proteinogenic amino acids. What groups of amino acids can be differentiated? Name one amino acid from each group and show their structure in Fisher projection.
Which protecting-group strategies are commonly applied and what are the advantages and disadvantages? Which protecting groups are used for the N-terminus and the side chains of amino acids?
Boc/BzL Strategy
What types of coupling reagents do exist and how do they work?
Coupling defined: Formation of a peptide bond between adjacent amino acids.
Process: Involves attack of amino group at carbonyl group of carboxy-containing component.
Activation: Accomplished by electron withdrawing group.
Activation forms: Can be shelf-stable reagent, compound of intermediate stability, or transient intermediate.
Explain solid-phase peptide synthesis. Show a synthetic route to the synthesis of H-Gly-Lys-Asp-OH. Which resins are suitable for this synthesis? What protecting groups and activators are needed?
In solid-phase peptide synthesis (SPPS) peptide sequences with an aspartate followed by a glycine are problematic. Very often, condensation of water is observed, and a side product with the same mass as the desired peptide sequence is found, which can be separated by HPLC. Please explain this finding. Which step in SPPS does promote this side reaction? What would be a suitable strategy to reduce side- product formation?
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