Show how solid-phase peptide synthesis would be used to make Ile-Gly-Asn.

Solid phase peptide synthesis involves addition of amino acid derivatives to a growing peptide chain which is fixed on a solid support and it also includes deprotection and washing steps that are required for the removal of unreacted groups and side products.

First step in the solid phase peptide synthesis of Ile-Gly-Asn is the protection of the N-terminal of the isoleucine amino acid by the protecting group, that is, benzyl chloroformate which is denoted by “Z” in the reaction sequence.

Benzyl chloroformate N-terminal protected amino acid

Then, N-terminal protected amino acid is treated with ethyl chloroformate which is the protecting group for C-terminal of amino acid. Then, introduction of second amino acid, that is glycine takes place to this growing peptide chain and lone pair of nitrogen in glycine attacks on carbonyl carbon or at C-terminal and in this process ester molecule leaves as a leaving group. Then, again ethyl chloroformate attacks at the C-terminal of this growing peptide chain which forms new peptide chain.

Finally, addition of third amino acid, that is, asparagine occurs to this growing peptide chain and formation of new peptide bond occurs and then deprotection of N-terminal is carried out using hydrogenation with palladium catalyst which gives us dipeptide Ile-Gly-Asp.

Ile-Gly-Asp