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What is the most effective protecting group for amino groups in organic synthesis and why? Provide examples of its use in peptide synthesis.

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The most effective protecting group for amino groups in organic synthesis is the tert-butyloxycarbonyl  t-Boc  group. The t-Boc group is widely used due to its stability, ease of installation, and removal under relatively mild conditions. It is particularly useful in peptide synthesis because it can protect the amino group from undesired side reactions during the coupling of amino acids.The t-Boc group can be introduced to an amino group using di-tert-butyl dicarbonate  Boc2O  in the presence of a base, such as triethylamine  Et3N . The reaction forms a stable carbamate, which can be deprotected using mild acidic conditions, such as trifluoroacetic acid  TFA  or hydrochloric acid  HCl  in an organic solvent like dichloromethane  DCM .In peptide synthesis, the t-Boc strategy is employed in the Boc-SPPS  Solid Phase Peptide Synthesis  method. Here's an example of its use in the synthesis of a dipeptide:1. The first amino acid, with a t-Boc protected amino group, is attached to a solid support  such as polystyrene resin  through its carboxyl group.2. The t-Boc protecting group is removed using TFA/DCM, revealing the free amino group.3. The second amino acid, also with a t-Boc protected amino group, is activated  usually as a symmetrical anhydride or an active ester  and coupled to the free amino group of the first amino acid on the resin.4. The t-Boc protecting group of the second amino acid is removed, and the process can be repeated for the synthesis of longer peptides.5. Once the desired peptide sequence is assembled, the peptide is cleaved from the resin and purified.The t-Boc protecting group is advantageous in peptide synthesis because it is orthogonal to the commonly used side-chain protecting groups, such as benzyl  Bn  or tert-butyl  tBu  groups. This orthogonality allows for selective deprotection of the amino group without affecting the side-chain protecting groups, enabling the synthesis of complex peptides with multiple protected functional groups.

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