Chemistry and heterocyclization of thiosemicarbazones

Synthesis and Molecular Docking of some new Thiazolidinone and Thiadiazole Derivatives as Anticancer Agents

New sets of functionalized thiazolidinone and thiadiazole derivatives were synthesized, and their cytotoxicity was evaluated on HepG2, MCF-7, HTC-116, and WI38 cells. The synthetic approach is based on the preparation of 4-(4-acetamidophenyl)thiosemicarbazide (4) and their thiosemicarbazones 5 a-e, which are converted to the corresponding thiazoldin-4-one compounds 6 a-e upon cyclization with ethyl bromoacetate. The thiadiazole compounds 9 and 12 were obtained by reacting 4-(4-acetamidophenyl)thiosemicarbazide with isothiocyanates and/or ethyl 2-cyano-3,3-bis(methylthio)acrylate, respectively. The thiazolidinone compounds 6 c and 6 e exhibited strong cytotoxicity against breast cancer cells, with an IC50 (6.70±0.5 μM) and IC50 (7.51±0.8 μM), respectively, very close to that of doxorubicin (IC50: 4.17±0.2 μM). In addition, the anti-cancer properties of the tested thiazolidinone and thiadiazole scaffolds were further explored by the molecular docking program (MOE)-(PDB Code-1DLS). Compounds 5 d, 5 e, 6 d, 6 e, and 7 have the best binding affinity, ranging from -8.5386 kcal.mol-1 to -8.2830 kcal.mol-1.

Investigation on the Stability of New Biologically Active Thiosemicarbazone- Derived Compounds by a Validated HPLC-PDA Method

Background:

New Chemical Entities (NCEs) could be generally exposed to several stress conditions of hydrolysis, oxidation, photolysis and thermal degradation in order to better characterize the compounds and to know if the degradation processes lead to generate undesired (or toxic) products.

Objective:

This paper reports the development and validation of an HPLC-PDA method for the qualiquantitative profiles determination and chemical-physical stability evaluation after forced decomposition studies of thiosemicarbazone-derived compounds endowed with interesting pharmacological activities.

Methods:

All compounds and two possible degradation products were resolved by using a Grace® C-18 (ODS) column (250 mm × 4.6 mm; 5 mm particle size) in gradient elution mode. The chromatographic analysis was run in 28 min. The analytical method was correctly validated using weighted-matrix matched standard curves in the following ranges: 1-100 µg mL-1 for the lead compounds, and 0.1-8 μg mL-1 for the two possible degradation products showing a good correlation coefficients (≥0.9756). Precision and trueness comply with International Guidelines on method validation.

Results:

The obtained results demonstrated an excellent stability of the thiosemicarbazone-derived products following the treatment with UV set at 254 nm and heat (at 80°C). In solution, however, the compounds showed different stability profiles.

Conclusion:

The results obtained through the forced degradation studies provided important information not only for handling, formulation and storage of the substances, but also for the possible chemical changes in order to increase the stability. Given the importance of the non-conventional dosage forms, the stability of the substances was also analyzed in the presence of widely used surfactants.

Synthesis and antiviral activity of camphor-based 1,3-thiazolidin-4-one and thiazole derivatives as Orthopoxvirus-reproduction inhibitors

The Orthopoxvirus genus belongs to the Poxviridae family and includes variola virus (smallpox), cowpox virus, monkeypox virus and vaccinia virus (VV). Smallpox is considered one of the great epidemic disease scourges in human history. It has currently been eradicated; however, it remains a considerable threat as a biowarfare or bioterrorist weapon. The poxvirus, VV, serves as a model virus from which new antiviral therapies against Orthopoxviruses can be identified. Here, a series of nitrogen-sulphur containing heterocycles such as 1,3-thiazolidin-4-one and thiazoles containing a 1,7,7-trimethylbicyclo[2.2.1]heptan scaffold were synthesized and screened for their antiviral activity. The bioassay results showed that the 4b, 4c and 4e thiazoles, which contained a substituted benzene ring, were able to inhibit VV reproduction with IC50 values in the 2.4-3.7 micromolar range whilst exhibiting moderate cytotoxicity. Among the thiazolidin-4-one derivatives, compound 8b, which contained a 4-methylbenzylidene group, displayed good inhibitory activity (IC50 = 9.5 μM) and moderate toxicity.

Synthesis and antibacterial and antifungal activities of N-(tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones

Background

Sydnone is a heterocycle that exhibits remarkable pharmacological activities, including antimicrobial, anti-inflammatory, analgesic, antipyretic and antioxidant activities. Thiosemicarbazones are of compounds that contain the –NHCSNHN=C< linkage group and are considerable interest because they exhibit important chemical properties and potentially beneficial biological activities. Similarly, thiosemicarbazones having carbohydrate moieties also exhibit various significant biological activities.

Results

The compounds of 3-formyl-4-phenylsydnones were obtained by Vilsmeyer-Haack’s formylation reaction and were transformed into thiosemicarbazones by condensation reaction with N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazide. Reaction were performed in the presence glacial acetic acid as catalyst using microwave-assisted heating method. Reaction yields were 43‒85 %. The antimicrobial activities of these thiosemicarbazones were screened in vitro by using agar well diffusion and MIC methods. Among these thiosemicarbazones, compounds 4k, 4l, 4m and 4n were more active against all tested bacterial strains, especially against S. epidermidis, B. subtilis and E. coli. The MIC values in these cases are 0.156, 0.156 and 0.313 μg/mL, respectively. All compounds showed weak to moderate antifungal activity against C. albicans and A. niger than nystatin (MIC = 0.156‒0.625 μg/mL vs. MIC = 0.078 μg/mL of nystatin), and thiosemicarbazones 4l, 4m and 4n exhibited significant activity with MIC = 0.156 μg/mL. These compounds also had good antifungal activity against F. oxysporum similarly to nystatin (MIC = 0.156 μg/mL). Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against three strains of fungal organisms.

Conclusions

In summary, we have developed a clean and efficient methodology for the synthesis of novel thiosemicarbazone derivatives bearing sydnone ring and d-glucose moiety; the heterocyclic and monosaccharide system being connected via ‒NH‒C(=S)NH‒N=C< linker using molecular modification approach. The methodology could be further extended and used for the synthesis of other thiosemicarbazones of biological importance. 4-Formyl-3-arylsydnone N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones have been synthesized under microwave-assisted heating conditions. Almost all obtained compounds showed remarkable activities against the tested microorganisms. Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against all tested strains of bacterial and fungal organisms.