Projects / Synthetic strategies / Synthetic building-blocks

Synthetic building-blocks to develop post translationally modified peptides

Profiles

In collaboration with:

Department of Medicine, Brigham and Women’s Hospital, Boston,  and Laboratory for Translational Research, Harvard Medical School, Cambridge, USA

Michael Chorev and Jose A. Halperin

One of the most studied post-translational modification (aberrant or native) by the PeptLab unit is glycosylation. In fact, glycosylation is the most important co- or posttranslational modification (PTM) of secreted proteins and plays a crucial role in several immune functions. Two main forms of protein glycosylation are generally found: O- and N-protein glycosylation. The synthesis of glycopeptides requires a combination of synthetic methods from both carbohydrate and peptide chemistry. To determine their activity relationships not only sugars but also control of their configuration and of the linkage with amino acids are needed.

Solid-Phase GlycoPeptide Synthesis (SPGPS) based on the building block approach is the most efficient method to obtain glycosylated peptides bearing different sugar moieties on the side chains of different amino acids. SPGPS requires an excess of building block units to achieve high yields, so it is necessary to prepare them in high quantity. For this reason it is fundamental to develop convenient synthetic pathways to glycosylated building blocks and efficient glycopeptide solid-phase synthetic pathways. In PeptLab several glycosylated building blocks orthogonally protected for SPGPS have been developed in large scale both by conventional approach and microwave assisted strategies.

In this context we developed the first synthesis of new Asparagine derivatives bearing alpha or beta- -ribose as pure anomers, linked by an N-glycosidic bond, on the side chain of the Asn residue orthogonally protected for Fmoc/tBu SPPS.

Moreover as glycation of proteins through non-enzymatic reactions between glucose or other reducing sugars and reactive amino groups represents one of the more abundant processes involved in post-translational modification of proteins, we focused our interest in developing Amadori-modified peptides. To this aim, the synthesis of Nα-protected-Nε-glycated-Lys building blocks has been set up. Our strategy offers a controlled side-specific introduction of Nε- Amadori-modified Lys residue into synthetic peptides during a stepwise assembly either in solution or in solid phase methodologies.