- Determination of the absolute stereochemistry and the activation barriers of thermally interconvertible heterocyclic compounds bearing a naphthyl substituent
-
The enantiotopic methyl signals of the compounds studied were resolved in the presence of the optically active chiral auxiliary (S)-(+)-2,2,2- trifluoroanthryl ethanol, [(S)-TFAE] via complex formation between (S)-TFAE and the respective compounds. Two different solvation models were proposed for both M and P conformations leading to the assignments of the 1H NMR signals and thus absolute conformations. The solvation models proposed also explained the strong temperature dependence of the 1H NMR signals upon cooling. The activation barriers for interconversion between the enantiomers of the compounds studied have been determined by either temperature dependent NMR or enantioresolution on a chiral sorbent via HPLC.
- Demir-Ordu, Oeznur,Yilmaz, Esra Muejde,Dogan, Ilknur
-
-
Read Online
- Synthesis, characterization, antibacterial and antioxidant potency of nsubstituted- 2-sulfanylidene-1,3-thiazolidin-4-one derivatives and QSAR study
-
Background: Rhodanine is known for its potential and important role in the medicinal chemistry since its derivatives exhibit a wide range of pharmacological activities such as antibacterial, antifungal, antidiabetic, antitubercular, anti-HIV, antiparasitic, antioxidant, anticancer, antiproliferative and anthelmintic agents. Objectives: Since N-substituted rhodanine synthons are rarely commercially available, it is desirable to develop a straightforward synthetic approach for the synthesis of these key building blocks. The objective was to synthesize a series of rhodanine derivatives and to investigate their antimicrobial and antioxidant activity. Also, in order to obtain an insight into their structure-activity relationship, QSAR studies on the antioxidant activity were performed. Methods: 1H and 13C FTNMR spectra were recorded on Bruker Avance 600 MHz NMR Spectrometer, mass analysis was carried out on ESI+ mode by LC-MS/MS API 2000. 2,2-Diphenyl-1- picrylhydrazyl radical scavenging activity (% DPPH) was determined in dimethylsulfoxide (DMSO) as a solvent. The antibacterial activity was assessed against Bacillus subtilis, Staphylococcus aureus (Gram positive) and Escherichia coli, Pseudomonas aeruginosa (Gram negative) bacteria in terms of the minimum inhibitory concentrations (MICs) by a modified broth microdilution method. Results: A series of N-substituted-2-sulfanylidene-1,3-thiazolidin-4-ones were synthesized and characterized by 1H NMR, 13C NMR, FTIR, GC MS, LCMS/MS and C,H,N,S elemental analysis. Most of the synthesized compounds showed moderate to excellent antibacterial activity (MIC values from 125 μg/ml to 15.62 μg/mL) and DPPH scavenging activity (from 3.60% to 94.40%). Compound 2-thioxo-3- (4-(trifluoromethyl)-phenyl)thiazolidin-4-one showed the most potent activity against Escherichia coli (3.125 μg/mL), equivalent to antibiotic Amikacin sulphate and against Staphylococcus aureus (0.097 μg/ml), 100 times superior then antibiotic Amikacin sulphate. It has also shown a potent antioxidant activity (95% DPPH scavenging). Two best QSAR models, obtained by GETAWAY descriptor R7p+, Balabans molecular connectivity topological index and Narumi harmonic topological index (HNar), suggest that the enhanced antioxidant activity is related to the presence of pairs of atoms higher polarizability at the topological distance 7, substituted benzene ring and longer saturated aliphatic chain in N-substituents. Conclusion: A series of novel N-substituted-2-thioxothiazolidin-4-one derivatives were designed, synthesized, characterized and evaluated for their antibacterial and antioxidant activity in vitro. Majority of the compounds showed excellent antibacterial activity compared to ampicillin and few of them have an excellent activity as compared to Chloramphenicol standard antibacterial drug. The QSAR study has clarified the importance of presenting a pairs of atoms higher polarizability, such as Cl and S at the specific distance, as well as the substituted benzene ring and a long saturated aliphatic chain in N-substituents for the enhanced antioxidant activity of 2-sulfanylidene-1,3- thiazolidin-4-one derivatives.
- Brahmbhatt, Harshad,Molnar, Maja,Pavi?, Valentina,Rastija, Vesna
-
p. 840 - 849
(2020/01/25)
-
- Chiral N-(o-aryl)-thiazolidinediones: Synthesis from rhodanines and investigation on rotational enantiomers by NMR spectroscopy
-
Sterically hindered N-(o-aryl)-rhodanines (a) (N-(o-aryl)-2-thioxo-4-thiazolidinones) have been synthesized and the N-(o-tolyl) and N-(o-chlorophenyl) derivatives have been converted to their dioxo analogs (b) (N-(o-aryl)-2,4-thiazolidine-diones). The chi
- Karatas,Koni,Dogan
-
p. 254 - 259
(2007/10/03)
-
- 1H and 13C NMR Studies on 3-Aryl-2-thioxo-4-oxazolidinones and 3-Arylrhodanines
-
3-Aryl-2-thioxo-4-oxazolidinones and 3-arylrhodanines have been studied for magnetic non-equivalence of diastereotopically related proton and 13C nuclei in rotational isomers, and for steric interactions between the aryl and heterocyclic moieties of these compounds.For the majority of rotational isomers the barriers to internal rotation about the aryl C-N bond were >100 kJ mol-1, due to the steric bulk of the thiocarbonyl group.Chemical isolation of several of the diastereomers was achieved.The enhanced steric effect and the difference in the electronic effect of the sulphur atom in relation to the oxygen atom appeared to have no influence on the small chemical shift differences of the rotational isomers, detected for some 1H and some 13C nuclei.
- Aksac, Zihni,Pinar, Esat,Icli, Siddik
-
p. 548 - 551
(2007/10/02)
-