Novel Oxadiazole Thioglycosides as Potential Anti-Acinetobacter Agents

The glycosylation of 1,3,4-oxadiazole-2-thiones has been performed with peracetylated β-pyranosyl bromide in the presence of potassium carbonate. Deprotection of acetylated thioglycosides was necessary for increasing their antibacterial effects. The structures of nucleosides were confirmed by 1H NMR, 13C NMR and HRMS. The anomeric protons of nucleosides c1-4 were assigned to the doublet, confirming the β-configuration. The synthesized compounds were tested for their antimicrobial activity against Acinetobacter calcoaceticus (Gram-negetive) strain in-vitro in comparison with Ampicillin as a reference drug which is normally used for treating such infections. The synthetic compounds showed different inhibition zones against tested bacterial strain. Thioglycoside derivatives of 1,3,4-oxadiazole-2-thiones (c set) were more active against Acinetobacter calcoaceticus ATCC 23055 than "parent" 1,3,4-oxadiazole-2-thiones (a set), confirming the relation between glyco-conjugation and increasing of antiproliferative activity of antibiotic agents. The best result belonged to nucleoside bearing 2-furyl moiety in its heterocyclic nucleus (c4). The existence of m-PhNO2 group as Ar in structures of a set and their corresponding sugar derivatives decreased the antibacterial activity of them in comparison with the rest of synthetic compounds.