Cyclic peptides are promising scaffolds for drug development, attributable in part to their increased conformational order compared to linear peptides. However, when optimizing the target-binding or pharmacokinetic properties of cyclic peptides, it is frequently necessary to “fine-tune” their conformations, e.g., by imposing greater rigidity, by subtly altering certain side chain vectors, or by adjusting the global shape of the macrocycle. This review systematically examines the various types of structural modifications that can be made to cyclic peptides in order to achieve such conformational control.

No abstract

The S N 2 reaction of nonyl bromide with sodium azide in DMF afforded Nonyl azide (1).Dgalactose has been protected by acetone in acidic medium gave 1,2:3,4-di-O-isopropylidene-α-Dgalactose (2). Williamson etherfication of (2) with propargyl bromide and sodium hydroxide yielded 6-O-(2-Propynyl)-1,2:3,4-di-O-isopropylidene-α-D-galactose(3). [2+3] Cycloaddition of (3) to nonyl azide using Click conditions afforded1-Nonyl-4-[(6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactose-6-yl)oxymethyl]1H-1,2,3-triazole(4). All prepared compounds have been characterized by FT-IR , 1 H NMR and 13 CNMR.

No abstract

Heptanol and octanol were converted into corresponding n-alkyl azides (2) using 48%HBr and sodium azide in two subsequent steps. Alkylation of diethyl malonate with allyl iodide and sodium ethoxide gave diethyl 2-allylmalonate (4) in a good yield. The reaction of compound (4) with urea in the presence of sodium ethoxide guide to obtain 5-allyl barbituric acid (5) in an excellent yield, while 4-allylpyrazolidine-3,5-dione (6) was obtained in very good yield by the reaction of compound (4) with hydrazine hydrate. The 1,3-dipolar cycloaddition reaction of compounds (5) and (6) with n-alkyl azides (2) afforded the targeted 1,2,3-triazolines (7a, 7b, 8a and 8b) in accepted yields. All the synthesized compounds had been characterized by TLC, FT-IR in addition to 1 H NMR (7b and 8a). The antibacterial activity of the final compounds were evaluated against two types of bacteria Staphylococcus Aureus and Escherichia Coli, the results showed that most of the new triazolines possess high biological activity.