Topological analysis and reactivity study of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone: a computational study.

CONTEXT: Quinolone derivatives have gathered major attention largely due to their wonderful biological activities. Quinolones are a class of molecules that are derived from quinolines and also extracted from natural sources. Most of these quinolones have significant medicinal properties ranging from antiallergenic and anticancer to antimicrobial activities. Some bacteria produce several 2-alkyl-4(1H)-quinolones. In past years, a variety of methods have been reported for the synthesis of quinolone derivatives. In this present work, structural, wave functional, and electronic properties of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone are investigated. From the calculated binding energies, it was found that the formation of dimers is thermodynamically favorable. The analysis of reactivity parameters confirms that the keto form is more reactive than the enol form and keto-keto dimer is more reactive than compared to all monomeric and dimeric forms of our studied compound. METHODS: Geometry optimizations of monomers and dimers of studied molecules were carried out using the B3LYP-D3(BJ)/ma-def2-TZVPP level of theory. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were calculated using the B3LYP/def2-TZVP level of theory. All DFT calculations were done with the ORCA 5.0.3 program. The reactivity parameters such as ionization potential, electron affinity, global hardness, global softness, electronegativity, chemical potential, and electrophilicity index were calculated. The nature of intermolecular interactions within the dimers was studied using topological analysis such as atoms in molecule (AIM) and reduced density gradient (RDG) surface analyses. To visualize the electron delocalization in the dimer electron localization function (ELF) and localized orbital locator (LOL) studies were also performed. The analyses such as AIM, RDG, ELF, and LOL were carried out by the multifunctional wavefunction analysis program Multiwfn 3.8.

Synthesis of the Hexasaccharide Related to the Exopolysaccharide from Lactobacillus mucosae VG1 through Regioselective Glycosylation.

Chemical synthesis of the hexasaccharide repeating unit associated with the exopolysaccharide of Lactobacillus mucosae VG1 is reported. The total synthesis is accomplished through a convergent [2 + 2 + 2] strategy using rationally protected monosaccharide derivatives. Chemoselective activation of the glycosyl donors and regioselective nucleophilicity of the acceptors were successfully employed throughout the chemical synthesis.

Chemical synthesis of the pentasaccharide related to the anti-inflammatory oleanane type saponins isolated from medicinal plant Aster tataricus L. f.

Total synthesis of the pentasaccharide related to the saponin isolated from the medicinal plant Aster tataricus L. f. is reported in the form of its allyl glycoside. The synthesis is accomplished by following a [3 + 2] block synthesis strategy where the trisaccharide acceptor and the disaccharide donor are rationally designed and obtained from semi-protected monosaccharides through stereoselective glycosylations either by activation of the thioglycoside or glycosyl trichloroacetimidate. The apiose moiety has been synthesized by literature procedure with little modification. The target pentasaccharide in the form of its allyl glycoside will be beneficial for further biological evaluation of the said structure and possible glycoconjugate formation as per need.

Synthesis of the tetrasaccharide repeating unit of the O-antigen from Pseudomonas putida BIM B-1100 having rare D-Quip3NAc.

Chemical synthesis of the complex tetrasaccharide repeating unit of the O-antigen from Pseudomonas putida BIM B-1100 is accomplished in the form of its 2-aminoethyl glycoside to leave the scope for further glycoconjugate formation without hampering the anomeric stereochemistry. A [2 + 2] strategy is followed to complete the total synthesis and a late stage TEMPO mediated oxidation is used to install the required uronic acid. A radical mediated 6-deoxygenation with subsequent protecting group manipulation strategy is used for the preparation of the rare D-FucpNAc and D-Quip3NAc derivatives from suitable d-glucosamine derivatives.

Concise chemical synthesis of the pentasaccharide repeating unit of the O-antigen from Escherichia albertii O2.

Total chemical synthesis of the pentasaccharide repeating unit of the O-antigen from Escherichia albertii O2 is accomplished by following a [3 + 2] strategy. The target pentasaccharide in the form of its 2-aminoethyl glycoside is particularly attractive as the free amine end can be coupled with suitable aglycon to make further glycoconjugate without affecting the anomeric stereochemistry. Phthalimido derivatives were used successfully as the precursor of the desired acetamido glucose moieties and ensured the 1,2-trans linkages.