Synthesis of some N4-substituted isatin-3-thiosemicarbazones

New Organotin (IV) Compounds Derived from Dehydroacetic Acid and Thiosemicarbazides: Synthesis, Rational Design, Cytotoxic Evaluation, and Molecular Docking Simulation

Organotin complexes were prepared through a one-pot reaction with three components by reacting thiosemicarbazide or 4-methyl-3-thiosemicarbazide or 4-phenylthiosemicarbazide, dehydroacetic acid (DHA) and dibutyl, diphenyl, dicyclohexyl, and bis[(trimethylsilyl)methyl]tin(IV) oxides; all complexes were characterized by infrared (IR), ultraviolet-visible (UV-vis), mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy. The 119Sn NMR revealed chemical shifts corresponding to a pentacoordinated environment in solution. The X-ray crystallography of the two complexes evidenced the formation of monomeric complexes with a pentacoordinated geometry around tin via three donor atoms from the ligand, the sulfur of the thiol, the nitrogen of the imine group, and the oxygen of the pyran ring. The geometries of the five-coordinated complexes 3a (Bu2SnL3), 3c (Ph2SnL3), and 3d (Cy2SnL3) acid were intermediate between square pyramidal and trigonal bipyramidal, and complex 1a (Bu2SnL1) adopted a bipyramidal trigonal geometry (BPT). The sulforhodamine B assay assessed the cytotoxicity of organotin(IV) complexes against the MDA-MB-231 and MCF-7 (human mammary adenocarcinoma) cell lines and one normal COS-7 (African green monkey kidney fibroblast). The IC50 values evidenced a significant antiproliferative effect on cancer cells; the complexes were more potent than the positive cisplatin control and the corresponding ligands, dehydroacetic acid thiosemicarbazone (L1), dehydroacetic acid-N(4)-methylthiosemicarbazone (L2), and dehydroacetic acid-N(4)-phenylthiosemicarbazone (L3). The IC50 values also indicated that the organotin(IV) complexes were more cytotoxic against the triple-negative breast cell line MDA-MB-231 than MCF-7, inducing significant morphological alterations. The interactions of organotin(IV) 1c (Ph2SnL1), 1d (Cy2SnL1), and 1e (((CH3)3SiCH2)2SnL1) were evaluated with ss-DNA by fluorescence; intensity changes of the fluorescence were indicative of the displacement of ethidium bromide (EB), confirming the interaction of the organotin(IV) complexes with ss-DNA; the results showed a DNA binding affinity. The thermodynamic parameters obtained through isothermal titration calorimetry showed that the interaction of 1c (Ph2SnL1), with ss-ADN, was exothermic. Molecular docking studies also demonstrated that the organotin(IV) complexes were intercalated in DNA by conventional hydrogen bonds, carbon-hydrogen bonds, and π-alkyl interactions. These complexes furthermore showed a greater affinity towards DNA than cisplatin.

Synthesis, crystal structure, molecular docking studies and bio-evaluation of some N4-benzyl-substituted isatin- 3-thiosemicarbazones as urease and glycation inhibitors

Fifteen N4-benzyl-substituted isatin-3-thiosemicarbazones 5a–o were synthesized and evaluated for their urease and glycation inhibitory potential. Lemna aequinocitalis growth and Artemia salina assays were also done to determine their phytotoxic and toxic effects. All compounds are potent inhibitors of the urease enzyme, displaying inhibition [half maximal inhibitory concentration (IC50)=1.08±0.12–11.23±0.19 μm] superior to that of the reference inhibitor thiourea (IC50=22.3±1.12 μm). Compounds 5c, 5d, 5h, 5j,k are potent antiglycating agents, showing glycation inhibitory activity better than that of the reference inhibitor rutin (IC50 values 209.87±0.37–231.70±6.71 vs. 294.5±1.5 μm). In the phytotoxicity assay, 11 thiosemicarbazones 5a–d, 5g, 5h, 5j–l, 5n,o are active, demonstrating 5–100% growth inhibition of L. aequinocitalis at the highest tested concentrations (1000 or 500 μg/mL). In the brine shrimp (A. salina) lethality bioassay, three derivatives 5b, 5j and 5o are active with median lethal dose (LD50) values of 3.63×10−5, 2.90×10−5 and 2.31×10−4 m, respectively.

Synthesis, cytotoxic and urease inhibitory activities of some novel isatin-derived bis-Schiff bases and their copper(ii) complexes

The putative binding mode of the most active compound 3b in the active site of Jack bean urease.

Synthesis and structure-activity evaluation of isatin-β-thiosemicarbazones with improved selective activity toward multidrug-resistant cells expressing P-glycoprotein

Cancer multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters presents a significant unresolved clinical challenge. One strategy to resolve MDR is to develop compounds that selectively kill cells overexpressing the efflux transporter P-glycoprotein (MDR1, P-gp, ABCB1). We have previously reported structure-activity studies based around the lead compound NSC73306 (1, 1-isatin-4-(4'-methoxyphenyl)-3-thiosemicarbazone, 4.3-fold selective). Here we sought to extend this work on MDR1-selective analogues by establishing whether 1 showed "robust" activity against a range of cell lines expressing P-gp. We further aimed to synthesize and test analogues with varied substitution at the N4-position, and substitution around the N4-phenyl ring of isatin-β-thiosemicarbazones (IBTs), to identify compounds with increased MDR1-selectivity. Compound 1 demonstrated MDR1-selectivity against all P-gp-expressing cell lines examined. This selectivity was reversed by inhibitors of P-gp ATPase activity. Structural variation at the 4'-phenyl position of 1 yielded compounds of greater MDR1-selectivity. Two of these analogues, 1-isatin-4-(4'-nitrophenyl)-3-thiosemicarbazone (22, 8.3-fold selective) and 1-isatin-4-(4'-tert-butyl phenyl)-3-thiosemicarbazone (32, 14.8-fold selective), were selected for further testing and were found to retain the activity profile of 1. These compounds are the most active IBTs identified to date.

Synthesis and Toxicity Evaluation of Some N4-Aryl Substituted 5-Trifluoromethoxyisatin-3-thiosemicarbazones

A series of twenty one N4-aryl substituted 5-trifluoromethoxyisatin-3-thiosemicarbazones 3a-3u was synthesized by the reaction of trifluoromethoxyisatin 1 with different arylthiosemicarbazides 2 in aqueous ethanol (50%), containing a few drops of acetic acid. Their structures were established on the basis of analytical (CHN) and spectral (IR, 1H-NMR, EIMS) data. All the synthesized compounds were evaluated for their toxicity potential by a brine shrimp lethality bioassay. Ten compounds i.e., 3a, 3e, 3i-3l and 3n-3q proved to be active in this assay, displaying promising toxicity (LD50 = 1.11 × 10-5 M - 1.80 × 10-4 M). Amongst these, 3k, 3n and 3o were found to be the most active ones (LD50 = 1.11 × 10-5 M - 1.43 × 10-5 M). Compound 3k showed the highest activity with a LD50 value of 1.11 × 10-5 M and can, therefore, be used as a lead for further studies. Structure-activity relationship (SAR) studies revealed that the presence of strong inductively electron-attracting trifluoromethoxy substituent at position-5 of the isatin moiety played an important role in inducing or enhancing toxic potentiality of some of the synthesized compounds.

4-(3-Fluoro-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

In the title compound, C₁₅H₁₁FN₄OS, there are three independent mol­ecules, each with a disordered 3-fluoro­phenyl group [occupancy ratios = 0.547 (17):0.453 (17), 0.645 (5):0.355 (5) and 0.626 (15):0.374 (15)] and displaying dihedral angles of 4.2 (3), 25.2 (6) and 32.4 (5)° between the 2-oxoindoline and fluoro-substituted phenyl rings. Strong intra­molecular N—H⋯N and N—H⋯O and weak intra­molecular C—H⋯S hydrogen bonds complete S(5) and S(6) ring motifs, while strong inter­molecular N—H⋯O hydrogen bonds inter­connect the three independent mol­ecules through R₃³(12) ring motifs. The three-mol­ecule units are in turn linked into polymeric sheets via C—H⋯F and C—H⋯S hydrogen bonds and π–π inter­actions [centroid–centroid distances in the range 3.520 (2)–3.820 (9) Å].

1-(2-Oxoindolin-3-yl-idene)-4-[2-(tri-fluoro-meth-yl)phen-yl]thio-semicarbazide

In the title compound, C₁₆H₁₁F₃N₄OS, the dihedral angle between the aromatic ring systems is 69.15 (10)°. Intra­molecular N—H⋯N and N—H⋯O hydrogen bonds generate S(5) and S(6) rings, respectively. A short N—H⋯F contact also occurs. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R₂²(8) loops. The dimers are linked by N—H⋯F hydrogen bonds, forming polymeric chains propagating in [100]. π–π inter­actions also exist between the centroids of the benzene rings of the 2-oxoindoline group at a distance of 3.543 (3) Å and a short C=O⋯π contact occurs. Two F atoms of the trifluoro­methyl group are disordered over two sets of sites in a 0.517 (8):0.483 (8) ratio.

4-(3-Iodo-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

In the title compound, C₁₅H₁₁IN₄OS, intra­molecular N—H⋯N, N—H⋯O and C—H⋯S inter­actions generate one S(5) and two S(6) ring motifs. In the crystal, mol­ecules form centrosymmetric dimers via pairs of N—H⋯O inter­actions, generating R₂²(8) ring motifs. In addition a short inter­molecular I⋯S contact of 3.352 (3) Å is observed.

1-Acetyl-3-[2-(2,3,5,6-tetra-fluoro-phen-yl)hydrazin-1-yl-idene]indolin-2-one

In the title compound, C₁₆H₉F₄N₃O₂, the dihedral angle between the aromatic ring systems is 4.10 (14)° and a bifurcated intra­molecular N—H⋯(O,F) hydrogen bond generates an S(6) ring for the O-atom acceptor and an S(5) ring for the F-atom acceptor. A short C—H⋯O conact also occurs. In the crystal, mol­ecules are linked by C—H⋯O inter­actions.

4-(3-Nitrophenyl)-1-(2-oxoindolin-3-ylidene)thiosemicarbazide

In the title compound, C₁₅H₁₁N₅O₃S, intra­molecular N—H⋯N hydrogen bonding forms an S(5) ring motif, whereas N—H⋯O and C—H⋯S inter­actions type complete S(6) ring motifs. The 2-oxoindoline and 3-methoxy­phenyl rings are almost planar, with r.m.s. deviations of 0.0178 and 0.0149 Å, respectively, and form a dihedral angle of 33.59 (3)°. In the crystal, mol­ecules are inter­linked through the nitro groups in an end-to-end fashion via N—H⋯O and C—H⋯O inter­actions.

4-(3-Methoxyphenyl)-1-(2-oxoindolin-3-ylidene)thiosemicarbazide

In the title compound, C₁₆H₁₄N₄O₂S, intra­molecular N—H⋯N hydrogen bonding forms an S(5) ring, whereas N—H⋯O and C—H⋯S inter­actions complete S(6) ring motifs. In the crystal, mol­ecules form inversion dimers due to N—H⋯O inter­actions. The dimers are inter­linked through N—H⋯S hydrogen bonds and π–π inter­actions occur with a centroid–centroid distance of 3.8422 (11) Å between the meth­oxy-containing benzene ring and the five-membered heterocyclic ring.

4-(2-Ethyl-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

The title compound, C₁₇H₁₆N₄OS, is stabilized in the form of a two-dimensional polymeric network due to inter­molecular N—H⋯S and N—H⋯O hydrogen bonds. An intra­molecular N—H⋯N hydrogen bond forms an S(5) ring, whereas inter­actions of the N—H⋯O and C—H⋯S types complete S(6) ring motifs. π–π inter­actions with a centroid–centroid distance of 3.6514 (10) Å are found between the ethyl-substituted benzene ring and the heterocyclic ring of the isatin derivative.

4-(5-Chloro-2-methyl-phen-yl)-1-[2-oxo-5-(trifluoro-meth-oxy)indolin-3-yl-idene]thio-semicarbazide

The asymmetric unit of the title compound, C₁₇H₁₂ClF₃N₄O₂S, contains two mol­ecules, which differ in their planarity and hydrogen bonding. In one mol­ecule, the 2-oxoindolin (C₈/N/O A), thio­semicarbazide (N₃/C/S B) and 5-chloro-2-methyl­phenyl (C₇/Cl C) units are planar with r.m.s. deviations of 0.0110, 0.0173 and 0.0259 Å, respectively. The dihedral angles A/B, B/C and A/C are 1.74 (15), 40.70 (13) and 41.00 (11)°, respectively. In the other mol­ecule the deviations are 0.0455, 0.0007 and 0.0143 Å, respectively, and the dihedral angles are 5.01 (14), 4.53 (16) and 3.38 (13)°, respectively. In both mol­ecules, intra­molecular N—H⋯N and N—H⋯O hydrogen bonds form S(5) and S(6) ring motifs, respectively and C—H⋯S interactions occur. In one of the molecules, an intramolecular C—H⋯F interaction is also present. In the crystal, the mol­ecules are linked by N—H⋯O, C—H⋯F, C—H⋯O and N—H⋯S hydrogen bonding, forming a polymeric network.