Levan Khelashvili

Benzotriazol-1-yl-sulfonyl azide for diazotransfer and preparation of azidoacylbenzotriazoles.

Benzotriazol-1-yl-sulfonyl azide, a new crystalline, stable, and easily available diazotransfer reagent provides N-(α-azidoacyl)benzotriazoles convenient for N-, O-, C- and S-acylations. The efficient syntheses of various amides, azido protected peptides, esters, ketones and thioesters is reported together with a wide range of azides (including α-azido acids from α- amino acids in partially aqueous conditions) and diazo compounds.

Gelation behavior of 2H-chromene N-acylamino acid conjugates.

2H-Chromene-based conjugates of N-acyl-1,omega-amino acids (5, 9a-f, 14a-f) of natural amino acids (10a,b) and of dipeptide (10c) are prepared (60-97%) by N-acylbenzotriazole methodology in aqueous media at 20 degrees C. Gelation properties of the corresponding sodium salts in DMF and DMSO are generalized with respect to an increase or decrease in the chain length of the spacer.

Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics

Summary The chemical similarity of antibacterial cyclic peptides and peptidomimetics was studied in order to identify new promising cyclic scaffolds. A large descriptor space coupled with cluster analysis was employed to digitize known antibacterial structures and to gauge the potential of new peptidomimetic macrocycles, which were conveniently synthesized by acylbenzotriazole methodology. Some of the synthesized compounds were tested against an array of microorganisms and showed antibacterial activity against Bordetella bronchistepica, Micrococcus luteus, and Salmonella typhimurium.

Spectroscopic and theoretical studies on intramolecular OH–π hydrogen bonding in 4-substituted 2-allylphenols

2-Allylphenol (1) constitutes a mixture of conformers, in which an OH-pi hydrogen bonded closed (1a) and open form (1b) can be distinguished. 4-Substituted 2-allyphenols (2-9) have been synthesised and investigated by theoretical and spectroscopic methods. In 1-9, the energy and the structure of the hydrogen bonds show distinct variation with substituents. In the PE spectra of most compounds, two ionisations can be distinguished which are related to the allylic pi(C[double bond]C) orbitals of the two conformers a and b and differ in energy by DeltaIP(C[double bond]C). Alternatively, DeltaIP(C[double bond]C) can be determined indirectly from comparison of the PE spectra of the respective phenols and anisoles with the same substituents. DeltaIP(C[double bond, length as m-dash]C) values between 0.3 and 1.1 eV were found. Frequency shifts Deltanu(OH) of the O-H vibration in CHCl3 solution were measured by IR spectroscopy. By means of correlation analysis of the relationship between the strength of the intramolecular hydrogen bond, DeltaIP(C[double bond]C), Deltanu(OH) values and substituent constants it is established how substituents in 4-position affect the intramolecular OH-pi hydrogen bond. The investigations demonstrate that the DeltaIP(C[double bond]C) data can be used as descriptors for this intramolecular interaction.

S- to N-Acyl transfer in S-acylcysteine isopeptides via 9-, 10-, 12-, and 13-membered cyclic transition states.

S‐Acyl cysteine peptides containing α‐, β‐ or γ‐amino acid residues undergo long‐range S‐ to N‐acyl transfer to give analogs of native tripeptides and tetrapeptides containing additional carbon atoms in the chain. The ease of intramolecular S → N‐acyl transfer relative to intermolecular transacylation is favored increasingly for 9 < 12 < 13 ~ 10‐membered cyclic transition states; the observed order is explained on conformational and intermolecular interaction considerations. Copyright

Dye Labelling of Nucleosides

Dye‐labelled nucleosides were obtained in 30–79% (average 45%) yields by treating N‐(4‐arylazobenzoyl)‐1H‐benzotriazoles 3a–b with appropriate nucleosides. Similarly, 3a–b afforded dye‐labelled threoninol conjugates in 55–89% (average 67%) yields. All novel products were characterized by NMR and elemental analysis.

Relative stabilities of 1- and 2-substituted 1,2,3-triazoles

N-(α-Aminoalkyl)-1,2,3-triazoles are potentially tautomeric between the 1- and 2-substituted forms. They exist in solution predominantly as 2-isomers as shown by 1 H and 13 C NMR; electron attracting substituents on the amino nitrogen increase the proportion of the 1-isomer in the equilibrium mixture.