Excessive and reckless use of antimicrobial drugs has led us to the occurrence of bacterial stance, which is a serious public health problem today. There are more and more bacterial species that develop resistance to antimicrobial drugs on a daily basis, which means that smaller infection presents larger risk. The search for new targets and new antibacterial drug is becoming important research area, because this is the only way we can successfully fight resistant bacteria.
Bacteria are single-celled organisms capable of rapid growth and rapid response to environmental changes. The bacterial cell wall is a solid frame composed of peptidoglycan. Peptidoglycan biosynthesis begins in the cytoplasm, where peptide units are synthesized, which are transported to the exterior of the cytoplasm and incorporated into pre-existing peptidoglycan. The action of many antibacterial drugs are based on inhibition of cell wall synthesis. The bio-orthogonal chemical approach is a tool for the recognition and labelling of glycoproteins in order to identify potential targets in a bacterial glycoprotein. In the biological system, azides are stable but at the same time well reactive with specific reagents such as phosphines or alkynes. Azido sugars easily pass through the cell membrane due to acetyl groups that increase permeability, so glycan labelling is also successful in vivo. Azido sugars are attached to the peptidoglycan chain by glycosyltransferases. The azide group is then attached to the probe by a selective chemical reaction and the molecule is fluorescently labelled.
The main goal for the master’s thesis was to synthesize and evaluate two azido derivatives of glucosamine. D-glucosamine hydrochloride was used as the starting compound for the synthesis of the first azido derivative of glucosamine, where we first protected amino group. Acetylation of four hydroxyl groups was followed by deprotection of amino group. Amide was formed with acylation and with nucleophilic substitution azide was prepared. We prepared glucosamine derivative with azide on acetyl group. N-acetylglucosamine was used as the starting compound for the synthesis of the second azido derivative of glucosamine, where tosylate was attached on C-6 and then acetylation of hydroxyl groups was performed. In the following, tosylate was substituted with azide by the mechanism of nucleophilic substitution. An azide derivative at C-6 was prepared. After synthesis of azido glucosamine derivatives, we performed click reaction with the alkyne coumarin molecule and the sugars were fluorescently labelled.
The success of each stage of synthesis was confirmed by chromatographic and spectroscopic methods. The adequacy of the reaction conditions of chemical reactions and the purity of products were confirmed by TLC analysis. Compounds were identified by recording mass and 1H NMR spectra.
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