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Updated: May 11, 2026

Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Understanding acid lability of cysteine protecting groups
Iván Ramos-Tomillero1, Lorena Mendive-Tapia, Miriam Góngora-Benítez
1Institute for Research in Biomedicine-IRB Barcelona, Baldiri Reixac 10, 08028-Barcelona, Spain.
Understanding acid-labile protecting groups for cysteine (Cys) is key for peptide synthesis. Carbocation stability during acid treatment directly impacts Cys protecting group removal, guiding the development of new peptide synthesis strategies.
Area of Science:
- Organic Chemistry
- Biochemistry
- Computational Chemistry
Background:
- Cysteine disulfide bonds stabilize peptide and protein structures.
- Proper protection of cysteine residues is essential for preventing side-reactions and ensuring correct disulfide bond connectivity during synthesis.
Purpose of the Study:
- To mechanistically study acid-labile cysteine protecting groups.
- To understand the factors influencing the acid-lability of these protecting groups.
- To identify promising new protecting groups for cysteine residues.
Main Methods:
- Mechanistic study of known and novel acid-labile Cys protecting groups.
- Analysis of carbocation stability generated during acid treatment.
- Computational chemistry (B3LYP/6-31G(d,p)) for geometry and energy optimization.
Main Results:
- Carbocation stability directly correlates with the efficiency of protecting group removal from Cys-containing peptides.
- Steric and conjugative effects govern carbocation stability.
- Diphenylmethyl (Dpm) group shows promising intermediate carbocation stability.
Conclusions:
- Carbocation stability is a critical factor in designing effective acid-labile Cys protecting groups.
- The Dpm group is proposed as a potentially valuable protecting group.
- Findings offer broader applicability for developing novel protecting group strategies in peptide chemistry.
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