CHIMIE BIO-ORGANIQUE DYNAMIQUE ET COMBINATOIRE IN SITU – CHIMIE BIO-ORGA

The aim of this project will be to develop and use innovative therapeutical concepts which combine an in situ dynamic and pre-organised chemical ligations (of which the click chemistry is an example) with a dynamic combinatorial chemistry. The concept we want to develop is to use a specific and biochemically important enzyme to direct the formation, the choice of its own inhibitor through the ligation of two different synthons. In other word the enzyme will catalysed either cinetically or thermodynamically the best, optimum inhibitors through a panel of substrate analogues in a combinatorial approach. We want to put forward the concept to introduce reversible ligations between two entities in so obtaining a dynamic selection. The therapeutical objectif of this project is directed toward the synthesis of inhibitors and alternative substrates of nucleoside monophosphate kinases (NMPK). Nucleotides and phosphorylated analogues are well known for their successful application in the treatment of important deseases such as cancer or viral pathologies These NMP kinases catalysed the reversible phosphate transfert from a nucleoside triphosphate (phosphate donor) to a monophosphate nucleoside (phosphate acceptor), which is then transformed into a diphosphate nucleoside. In our approach, the uridine (or cytidine) monophosphate kinase (UMPK) act as a catalytic-template for the selection of the best substrate and the synthesis of an optimised inhibitor : substrates analogues and mimics would fit inside the enzymatic pocket and will be linked through reversible or irreversible reactions. Our project aim to develop a new area of innovative research inside the Institute to support and develop medicinal chemistry in enhancing selectivity and potency of new drugs. Developping this dynamic medicinal chemistry needs three distinct steps : a- preparation of the acceptor mimics, b- the donor analogues and c- testing the in-situ ligation with the enzymes. All the analogues (donor or acceptor) will be tested as inhibitors or substrates of the enzymes in competition with MABA-CDP (a fluorescent probe) before any in-situ ligation experiments. The core of our project is the elaboration of the C-3 linkers which will be based on dimeric structures of synthons derived from glycerol chemistry. Chemical ligation needs bio-compatible functions allowing some physiological stability and keeping their reactivities under such conditions (mainly the pH). In fact just a small amount of reactive functions is compatible with such conditions, and they will be tested in our project. The native peptide ligation has been develop specifically for peptide synthesis but has never been applied for in situ chemoselective ligation. This project will help to explore the scope of this function in such a system. Reversible Michael reactions will be explore on a panel of acceptors. The Michael acceptors will be modified on the EWG (electron withdrawing group) to introduce carboxylate, sulfonate or phosphonate groups. Else the acceptor function could also be an isothiocyanate function (ITC) which has shown reversible properties upon thiol additions. These functions will be anchored on a C-3 carbon structures. These backbones will be derived from glycerol or from selectively chosen monosaccharide to introduce chirality. These approaches will enhance the flexibility and functionalities of the molecules. This new chemistry derived from glycerol and monosaccharides will be used to create linkers for the purpose of this project. Glycerol approach will used the combination of less toxic glycidol derivatives. Monosaccharide approach will devise alternative approaches of enantomerically pure and highly functionalised analogues. Further the chemistry of C-3 synthons will explore the reactive species implicated in the reversible or irreversible ligation. The application of sulfur chemistry (Michael additions, thiols nucleophiles) develop from recent years in the lab will be the basis of a tunable chemistry. Then different structural sub-units are consider for the in situ ligation: (A) Nucleosides analogues based on the close analogy with cidofovir structure ; (B) a strong Pharmacomodulation approach to develop ATP analogues based on known pharmacophoric inhibitors of kinases. (C) The enzyme interactions of both type of analogues either (A) as substrate of the enzyme or (B) as inhibitors and further the combinatorial analysis of the reversible or irreversible ligations analysed with or without the enzyme. This original and ambitious project combine some short term objectives together with middle and long term research at the frontier of biology and chemistry. The collaborations, within the institute and outside for the biological approach will challenge the concept of a dynamic combinatorial chemistry in complex biosystems for the development of original methods of synthesis, analysis, and create new ligands for therapeutical applications.