Microwave-assisted Synthesis and Bioevaluation of Some Semicarbazones

Synthesis, characterization, X-ray structure, computational studies, and bioassay of novel compounds combining thiophene and benzimidazole or 1,2,4-triazole moieties

BACKGROUND

Due to their interesting and versatile biological activity, thiophene-containing compounds have attracted the attention of both chemists and medicinal chemists. Some of these compounds have anticancer, antibacterial, antiviral, and antioxidant activity. In addition, the thiophene nucleus has been used in the synthesis of a variety of heterocyclic compounds.

RESULTS

In the present work, two novel thiophene-containing compounds, 4-phenyl-2-phenylamino-5-(1H-1,3-a,8-triaza-cyclopenta[α]inden-2-yl)-thiophene-3-carboxylic acid ethyl ester (3) and 5-(1H-Imidazo[1,2-b] [1,2,4] triazol-5-yl)-4-phenyl-2-phenylamino-thiophene-3-carboxylic acid ethyl ester (4), have been synthesized by reaction of 5-(2-bromo-acetyl)-4-phenyl-2-phenylaminothiophene-3-carboxylic acid ethyl ester (2) with 2-aminobenzimidazole and 3-amino-1H-1,2,4-triazole in the presence of triethylamine, respectively. Compound 2, on the other hand, was prepared by bromination of 5-acetyl-4-phenyl-2-phenylaminothiophene-3-carboxylic acid ester (1). Structures of the newly prepared compounds were confirmed by different spectroscopic methods such as ¹H-NMR, ¹³C-NMR, and mass spectrometry, as well as by elemental analysis. Furthermore, bromination of compound 1 led to the formation of two constitutional isomers (2a and 2b) that were obtained in an 80:20 ratio. Molecular structures of 2b were confirmed with the aid of X-ray crystallography. Compound 2 was crystallized in the triclinic, P-1, a = 8.8152 (8) Å, b = 10.0958 (9) Å, c = 12.6892 (10) Å, α = 68.549 (5)°, β = 81.667 (5)°, γ = 68.229 (5)°, V = 976.04 (15) Å³, Z = 2, and was found in two isomeric forms regarding the position of the bromine atom. The antibacterial and antifungal activities of the prepared compounds were evaluated.

CONCLUSIONS

Three new thiophene derivatives were synthesized in good yield. Antimicrobial screening revealed that compound 3 was a promising candidate as a potential antibacterial and antifungal agent; it exhibits remarkable activity against the studied bacterial strains, especially the gram negative bacteria E. coli in addition to some fungi. More work is needed to evaluate its safety and efficacy.

Antimicrobial Activity of Some Novel Armed Thiophene Derivatives and Petra/Osiris/Molinspiration (POM) Analyses

Tetrasubstituted 2-acetylthiophene derivative 5 was synthesized and then condensed with various nitrogen nucleophiles such as 5-amino-1,2,4-triazole, 2-aminobenzimidazole, aniline or p-chloroaniline to afford the corresponding iminothiophene derivatives 6-8a,b. Condensation of thiophene 5 with malononitrile as carbon nucleophile afforded compound 9, which underwent nucleophilic addition with DMF-DMA to afford compound 10. The newly synthesized products were characterized by elemental analysis, IR, MS, ¹H-(13)C-NMR and CHN analysis and then evaluated for their antimicrobial activity. Results of the in vitro antibacterial activity showed that thiophene derivative 7 was found to be more potent than the standard drug gentamicin against Pseudomonas aeruginosa. Some of these compounds showed potential antimicrobial activities. Molecular docking and Osiris/Molinspiration analyses show the crucial role and impact of substituents on bioactivity and indicate the unfavorable structural parameters in actual drug design: more substitution with electronic donor group doesn't guarantee more effective bioactivity. This study should greatly help in an intelligent and a controlled pharmacomodulation of antibiotics.

Potentially bioactive organotin(IV) compounds: synthesis, characterization, in vitro bioactivities and interaction with SS-DNA

Fourteen new organotin(IV) complexes with general formula R2SnL2 or R3SnL where R = CH3, C2H5, C4H9, C6H5, C6H11, CH2-C6H5, C(CH3)3, C8H17 and L = N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide were synthesized and characterized by elemental analyses, FT-IR, NMR ((1)H, (13)C and (119)Sn), mass spectrometry and single crystal X-ray structural analysis. Crystallographic data for four triorganotin(IV) complexes (R3SnL, R = CH3, C2H5, C4H9, CH2-C6H5) showed the tin has approximate trigonal bipyramidal geometry with the R groups in the trigonal plane. The carboxylate groups of ligands L bridge adjacent tin atoms, resulting in polymeric chains. In case of the diorganotin(IV) derivatives a six-coordinate geometry at the tin atom is proposed from spectroscopic evidence. The Me-Sn-Me bond angle in complex 7 was determined from the (2)J[(119)Sn-(1)H] value as 166.3° that falls in the range of six-coordinate geometry. The ligand and its complexes (1-14) were screened for their antimicrobial, antitumor, cytotoxic and antileishmanial activities and found to be biologically active. The ligand and its complexes bind to DNA via intercalative interactions resulting in hypochromism and minor bathochromic shifts as confirmed by UV-visible spectroscopy. Based on in vitro studies such as the potato disc method, the synthesized compounds were found to possess significant antitumor activity. Also, from cytotoxicity and DNA interaction studies, these compounds can also be used for the prevention and treatment of cancer. Gel electrophoresis assay was used to investigate the damage to double stranded super coiled plasmid pBR322 DNA by the synthesized compounds and compounds 1 and 7 were found to cause the maximum damage. All the synthesized compounds exhibit strong antileishmanial activity that was even higher than that of Amphotericin B, with significant cytotoxicity. This study, therefore, demonstrated the potential use of these compounds as source of novel agents for the treatment of leishmaniasis.