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Isosteric replacement of amide bond(s) of peptides with surrogate groups is an important strategy for the synthesis of peptidomimetics (pseudo-peptides). Triazole is a well-recognized bio-isostere for peptide bonds, and peptides with one or more triazole units are of great interest for different applications. We have used a catalyst-free and solvent-free method, viz., topochemical azide–alkyne cycloaddition (TAAC) reaction, to synthesize pseudo-proteins with repeating sequences. A designed β-sheet-forming l-Ala-l-Val dipeptide containing azide and alkyne at its termini (N3-Ala-Val-NHCH2C≡CH, 1) was synthesized. Single-crystal XRD analysis of the dipeptide 1 showed parallel β-sheet arrangement along the b-direction and head-to-tail arrangement of such β-sheets along the c-direction. This head-to-tail arrangement along the c-direction places the complementary reacting motifs, viz., azide and alkyne, of adjacent molecules in proximity. The crystals of dipeptide 1, upon heating at 85 °C, underwent crystal-to-...

The research was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ERC-2016-StG, grant number 715062-HiChemSynPro).; International audience; Chemical composition of tumor suppressor protein p53 is altered via multiple post-translational modifications which modulate its cellular lifetime and interactions with other biomolecules. Here we report total chemical synthesis of a 61-residue form of transactivation domain (TAD) of p53 based on native chemical ligation of three peptide segments. The experiments to characterize its binding to nuclear co-activator binding domain (NCBD) of CREB-binding protein confirmed native-like induced folding upon binding to NCBD. Thus, the synthetic approach described herein can be useful for the preparation of various post-translationally modified analogues of TAD-p53 for further functional biochemical and biophysical studies.

We report a bio-inspired, strain driven epimerization of trans-ketals to cis-ketals through an enolate intermediate. Swern oxidation of a hydroxyl group adjacent to a trans-ketal effects both oxidation and its epimerization to cis-ketal. This novel and general strategy allows inversion of up to three contiguous stereocenters and has been illustrated by the synthesis of several unnatural/rare isomers of carbohydrates/cyclitols from their naturally abundant isomers.