C-H activation of benzene by platinum(II) complexes with cyclometalated phosphine ligands

The bulky phosphine ligands di-tert-butyl(1-naphthyl)phosphine (1) or di-tert-butyl(N-indolyl)phosphine (2) react at room temperature with [(μ-SMe₂)PtMe₂]₂. Coordination of the phosphine and C-H bond activation at an sp² carbon of the ligand with the release of methane takes place to form the PC cyclometalated products [(PC)PtMe(SMe₂)] (3 or 4, respectively). The cyclometalated complexes 3 and 4 have both been characterized by X-ray crystallography. Complexes 3 and 4 were each observed to undergo intermolecular activation of arene C-H bonds. Upon thermolysis in benzene, complexes 3 and 4 react to eliminate methane and yield isolable platinum(II)-phenyl complexes.     

Bioactive butylphthalide derivatives from Ligusticum chuanxiong

Seven new butylphthalide derivatives, ligusticumolide A-G (1–7), together with two known butylphthalide derivatives (8–9) were isolated from an ethanol extract of Ligusticum chuanxiong Hort. The structures of these derivatives were elucidated from analysis of 1D/2D NMR, UV, IR and HRESIMS data. The absolute configurations of these derivatives were determined by electronic circular dichroism (ECD) calculations and Mosher′s method. Ligusticumolide A (1) and ligusticumolide B (2) are enantiomers that were obtained by chiral separation. Ligusticumolide C (3) and ligusticumolide D (4) are diastereomers. All of the compounds were evaluated for their hepatoprotective activity against N-acetyl-p-aminophenol-induced HepG2 cell injury. Compounds 4, 5, and 7–9 showed more significant hepatoprotective activity than that of the positive control drug (bicyclol) at a concentration of 10 μM (p < 0.01).     

Synthesis and complexation of tetrakis(diphenylphosphinomethyl)calix[4]arene adopting the 1,3-alternate conformation

Novel upper-rim modified tetraphosphinocalix[4]arenes (5a-b) adopting 1,3-alternate conformation have been synthesized. Reaction of 5,11,17,23-tetrachloromethyl-25,26,27,28-tetrahydroxycalix[4]arene (1) with Ph₂POEt gave 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2). Tetra-O-substitution of 2 with n-propyl iodide or benzyl bromide in the presence of K₂CO₃ carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxy-(3a) or -benzyloxycalix[4]arene (3b), whereas di-O-substituted calix[4]arene, 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4), was obtained exclusively when Na₂CO₃ was used as base. Reduction of 3a-b with PhSiHCl₂ afforded 5,11,17,23-tetrakis(diphosphinomethyl)-25,26,27,28-tetrapropoxy-(5a) and -tetrabenzyloxycalix[4]arene (5b). ¹H and ¹³C NMR analysis reveals that the phosphines (5a-b) and the tetra-O-substituted phosphine oxides (3a-b) adopt 1,3-alternate conformation, while the parent tetrahydroxy-(2) and the di-O-propylated phosphine oxide (4) adopt cone-conformation. The X-ray structure indicates that the calix[4]arene moieties in 4 a pinched-cone conformation in solid state. Complexation of the phosphine ligand (5a) with [RuCl₂(p-cymene)]₂ affords the tetranuclear complexes, [{RuCl₂(p-cymene)}₂ · 5a] (6), as 1,3-alternate conformer.     

The complexes: RhCl(P-N)(THP), where P-N is P,N-chelated o-diphenylphosphino-N,N-dimethylaniline and THP is tris(hydroxymethyl)phosphine, and RhCl[(O)P-N][THP(O)] containing O-bonded phosphine oxides

The complex RhCl(P-N)(THP) (1) is synthesized under argon from RhCl(cod)(THP) and P-N, and is structurally characterized; P-N = P,N-chelated o-diphenylphosphino-N,N-dimethylaniline, THP = tris(hydroxymethyl)phosphine, and cod = 1,5-cyclo-octadiene. The corresponding synthesis in air yields RhCl[(O)P-N][THP(O)] (2), containing O-bonded phosphine oxide ligands.     

Synthesis and biological evaluation against Leishmania amazonensis of a series of alkyl-substituted benzophenones

Nine O-alkyl and O-prenyl derivatives were synthesized from commercial 2,4-dihydroxybenzophenone, 4,e4,4′-dihydroxybenzophenone and were evaluated for their leishmanicidal activity against promastigote forms of Leishmania amazonensis, as well their toxicity in murine macrophages. All derivatives exhibited better biological activity than their hydroxylated benzophenones precursors, and new compound LFQM-123 (3c) was 250-fold more active than its precursor 4,4′-dihydroxybenzophenone (3). Moreover, some of the results were comparable to the standard drug Amphotericin B, suggesting that the increase in lipophilicity could facilitate protozoa membrane permeation. In this study we confirmed that benzophenone derivatives exhibit leishmanicidal properties, with relatively low toxicity, and thus could be exploited as promise prototypes for the design and development of new drug for the treatment of leishmaniasis.     

Application of palladium(II) complex with bidentate phosphine sulfide ligands to palladium-catalyzed C-C coupling reaction

A phosphine sulfide Pd(II) complex, [Pd(p₂S₂)₂](BF₄)₂ (1) (p₂S₂ = 1,2-bis(diphenylphosphino)ethane disulfide), was synthesized and characterized by an X-ray crystal structure analysis and ³¹P NMR spectroscopy. The p₂S₂ ligand exchange rate of 1 with free p₂S₂ in chloroform was revealed to be comparable to the general solvent exchange rate on Pd(II). The catalytic activity of 1 was evaluated by carrying out the Heck reaction. The diminishing of the induction period and acceleration of the reaction were observed for 1 by comparing the phosphine Pd(II) complexes with a leaving chloro ligand, [PdCl(p₃)]Cl (p₃ = bis[2-(diphenylphosphino)ethyl]phenylphosphine) and [PdCl(pp₃)]Cl (pp₃ = tris[2-(diphenylphosphino)ethyl]phosphine), and the catalytic activity was comparable to that of the phosphine Pd(0) complex, [Pd(PPh₃)₄]. Such a high catalytic activity of 1 is attributed to the π-accepting ability of the phosphine sulfide S atom which stabilizes the catalytically active Pd(0) species electronically and weak σ-donation of the S atom which does not block the formation and a subsequent reaction of the Pd(II) substrate adduct in the catalytic cycle.     

Synthesis,crystal structure and biological activity of novel analogues of tricyclic drugs

A series of fourteen novel, eight-membered lactam- and dilactam-based analogues of tricyclic drugs were obtained in a simple one-pot procedure. Crystal structures of two compounds were determined by single-crystal X-ray diffraction analysis and their selected structural features were discussed and compared with those of imipramine and dibenzepine. Affinity of developed molecules for histamine receptor H₁, serotonin receptors 5-HT_1A, 5-HT_2A, 5-HT₆, 5-HT₇, serotonin transporter (SERT) and dopamine receptor D₂ was determined. The commercial drug dibenzepine was also checked on these molecular targets, as its mechanism of action is largely unknown. Two derivatives of 11,12-dihydrodibenzo[b,f]azocin-6(5H)-one (7,8) and two of dibenzo[b,f]azocin-6(5H)-one (9,10) were found to be active toward the H₁ receptor in sub-micromolar concentrations.     

Synthesis and biological activities of novel pyrazolomatrine derivatives

In continuation of our program aimed at the development of new natural product-based pesticides, a series of novel pyrazolomatrine derivatives were prepared by structural modifications of matrine, isolated as a quinolizidine alkaloid from the roots of Sophora flave. Their structures were confirmed by ¹H NMR, HRMS, etc. Moreover, the steric structures of three compounds were determined by single-crystal X-ray diffraction. Among all derivatives, 19-(naphthyl-2-oyl)pyrazolomatrine (5y) showed 3.13-fold more potent acaricidal activity than its precusor matrine against Tetranychus cinnabarinus; 19-(4-methylbenzoyl)pyrazolomatrine (5j) and 19-(3,5-dimethylbenzoyl)pyrazolomatrine (5k) displayed the promising aphicidal activity against Aphis citricola van der. Their structure-activity relationships were also observed.     

Synthesis,crystal and antibacterial studies of diversely functionalized tetrahydropyridin-4-ol

In an effort to expand the spectrum of antibacterial activity associated with piperidin-4-one derivatives, we have synthesized two series of 3-carboxyethyl-2,6-diphenyl-4-hydroxy-Δ³-tetrahydropyridine derivatives bearing diversified heterocyclic and aromatic systems at the nitrogen atom through acetyl (6–18) and 2-propanoyl (9–31) linkers. Unlike acetyl derivatives, NMR spectral pattern of the propanoyl counterparts revealed the existence of pair of rotational isomers (syn and anti) in solution at room temperature due to the hindered rotation about N–CO bond. X-ray crystal studies of 9 and 24 clearly pointed out that all the compounds existed in only one form particularly, in stable syn form in solid state. Each of the compounds was screened for their in vitro antibacterial activity against nine human pathogenic Gram-positive strains including multiple drug resistant organisms and seven problematic Gram-negative strains. Among the various heterocycles examined here, imidazole substituted derivatives 12 and 25 exhibited antibacterial activity approaching that of Linezolid and Trovafloxacin drugs particularly against multiple resistant Enterococcus faecium-VanA phenotype strains.     

Derivatives (halogen,nitro and amino) of 8-hydroxyquinoline with highly potent antimicrobial and antioxidant activities

8-Hydroxyquinoline (8HQ) compounds have been reported to possess diverse bioactivities. In recent years, drug repositioning has gained considerable attention in drug discovery and development. Herein, 8HQ (1) and its derivatives (2–9) bearing various substituents (amino, nitro, cyano and halogen) were investigated for their antimicrobial against 27 microorganisms (agar dilution method) and antioxidant (DPPH method) activities. The parent 8HQ (1) exerted a highly potent antimicrobial activity against Gram-positive bacteria including diploid fungi and yeast with MIC values in the range of 3.44–13.78 μM. Moreover, the halogenated 8HQ, especially 7-bromo-8HQ (4) and clioquinol (6), displayed a high antigrowth activity against Gram-negative bacteria compared with the parent compound (1). Apparently, the derivatives with a relatively high safely index, e.g., nitroxoline (2), exhibited strong antibacterial activity against Aeromonas hydrophila (MIC=5.26 μM) and selectively inhibited the growth of P. aeruginosa with the MIC value of 84.14 μM; cloxyquin (3) showed a strong activity against Listseria monocytogenes and Plesiomonas shigelloides with MIC values of 5.57 and 11.14 μM, respectively. Most compounds displayed an antioxidant activity. Specifically, 5-amino-8HQ (8) was shown to be the most potent antioxidant (IC₅₀=8.70 μM) compared with the positive control (α-tocopherol) with IC₅₀ of 13.47 μM. The findings reveal that 8HQ derivatives are potential candidates to be further developed as antimicrobial and antioxidant agents.     

Synthesis of methanesulphonamido-benzimidazole derivatives as gastro-sparing antiinflammatory agents with antioxidant effect

A series of 5-methanesulphonamido benzimidazole derivatives were designed by combining the structural features of clinically useful anti-inflammatory drugs (nimesulide and rofecoxib) and antiulcer drugs (lansoprazole, omeprazole, etc.) based on physicochemical and 3D similarity studies. The compounds were evaluated for their anti-inflammatory activity in carrageenan induced rat paw edema model taking rofecoxib and indomethacin as standard drugs. In vitro antioxidant activity of the compounds was assessed by potassium ferricyanide reducing power (PFRAP) assay. The compounds 9, 10 and 11 showed anti-inflammatory activity comparable to the standard group and were also non-ulcerogenic at the test doses. Compounds 6–11 exhibited good antioxidant effect in the concentration range (1.0–50.0 µmol/ml. Preliminary theoretical ADME profiling of the compounds based on computation of selected physicochemical properties showed an excellent compliance with Lipinski’s rule.     

Synthesis,in-vitro α-glucosidase inhibition,antioxidant, in-vivo antidiabetic and molecular docking studies of pyrrolidine-2,5-dione and thiazolidine-2,4-dione derivatives

α-Glucosidase is considered as a therapeutic target for the treatment of type 2 diabetes mellitus (DM2). In current study, we synthesized pyrrolidine-2,5-dione (succinimide) and thiazolidine-2,4-dione derivatives and evaluated for their ability to inhibit α-Glucosidase. Pyrrolidine-2,5-dione derivatives (11a–o) showed moderate to poor α-glucosidase inhibition. Compound 11o with the IC₅₀ value of 28.3 ± 0.28 µM emerged as a good inhibitor of α-glucosidase. Thiazolidine-2,4-dione and dihydropyrimidine (TZD-DHPM) hybrids (22a–c) showed excellent inhibitory activities. The most active compound 22a displayed IC₅₀ value of 0.98 ± 0.008 µM. Other two compounds of this series also showed activity in low micromolar range. The in-vivo antidiabetic study of three compounds 11n, 11o and 22a were also determined using alloxan induced diabetes mice model. Compounds 11o and 22a showed significant hypoglycemic effect compared to the reference drug. In-vivo acute toxicity study showed the safety of these selected compounds. In-silico docking studies were carried out to rationalize the in-vitro results. The binding modes and bioassay results of TZD-DHPM hybrids showed that interactions with important residues appeared significant for high potency.     

Design,synthesis, and anticonvulsant activity of new N-Mannich bases derived from spirosuccinimides and spirohydantoins

The synthesis and anticonvulsant properties of new N-Mannich bases of [7,8-f]benzo-2-aza-spiro[4.5]decane-1,3-diones (5a–h) and [7,8-f]benzo-1,3-diaza-spiro[4.5]decane-2,4-diones (7a–h) were described. Initial anticonvulsant screening was performed using intraperitoneal (ip) maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizures tests. The neurotoxicity was determined applying the rotarod test. The majority of compounds were effective in the MES or/and scPTZ screen. The quantitative studies showed that several molecules were more potent than phenytoin, used as reference drug. Selected derivatives were screened in the 6-Hz test and also assessed for potential activity against nerve agents using the Pilocarpine Induced Status Prevention model. To explain the possible mechanism of anticonvulsant action, for chosen active derivatives, their influence on voltage-dependent Na⁺ channel were tested in vitro.     

Design and synthesis of novel pyridazinoquinazoline derivatives as potent VEGFR-2 inhibitors: In vitro and in vivo study

Worldwide, Hepatocellular Carcinoma (HCC) endures to be a prominent cause of cancer death. Treatment of HCC follows multiple therapies which are not entirely applicable for treatment of all patients. HCC usually arises contextual to chronic liver diseases and is often discovered at later stages which makes treatment options more complex. The present study aimed at design, synthesis & evaluation of new pyridazinoquinazoline derivatives as potential nontoxic anti-hepatocellular carcinoma (HCC) agents, through inhibition of Vascular endothelial growth factor -2 (VEGFR-2). Novel Pyridazino[3, 4, 5-de]quinazoline derivatives (2-6) were designed & synthesized. Their structures were confirmed via spectral and microanalytical data. They were tested for their in vitro VEGFR-2 inhibition & anticancer activity against human liver cancer cell line (HEPG-2). Molecular docking was investigated into VEGFR-2 site. In vivo studies of VEGRF-2 inhibition and the anti-apoptotic effect of the new compounds were determined in liver of irradiated rats. Toxicity of synthesized compounds was also assessed. The results showed that compounds 3-6 have significant antitumor activity and proved to be non-toxic. The ethoxy aniline derivative 6, exhibited the highest activity both in vitro and in vivo compared to the reference drug used, sorafenib. Compound 6 could be considered a promising nontoxic anti HCC agent and this could be partially attributed to its VEGFR-2 inhibition. Future preclinical investigation would be carried out to confirm the specific and exact mechanism of action of these derivatives especially compound 6 as an effective pharmaceutical agent after full toxicological and pharmacological assessment.     

Synthesis of novel indenoquinoxaline derivatives as potent α-glucosidase inhibitors

A series of new N-(11H-Indeno[1,2-b]quinoxalin-11-ylidene)benzohydrazide derivatives (3a–3p) were synthesized and evaluated for their α-glucosidase inhibitory activity. The synthesized compounds 3d, 3f, 3g, 3k, 3n, 3p and 4 showed significant α-glucosidase inhibitory activity as compared to acrabose, a standard drug used to treat type II diabetes. Structures of the synthesized compounds were determined by using FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry and elemental analysis techniques.     

Design,synthesis, modeling studies and biological evaluation of thiazolidine derivatives containing pyrazole core as potential anti-diabetic PPAR-γ agonists and anti-inflammatory COX-2 selective inhibitors

Nowadays, diabetes and its associated inflammatory complications are important public health problems worldwide. Market limitations of drugs with dual actions as anti-inflammatory (AI) and anti-diabetic have been led to a temptation for focusing on the discovery and development of new compounds with potential AI and anti-diabetic activities. Herein, we synthesized two new series containing pyrazole ring with vicinal diaryl rings as selective COX-2 moiety and thiazolidindione (series 12a-f) or thiazolidinone (series 13a-f) as anti-diabetic moiety and the two moieties were linked together with methylene or methylenehydrazone functionality. The two series were evaluated for their COX inhibition, AI activity and ulcerogenic liability and for the anti-diabetic activity; 12a-f and 13a-f were assessed in vitro against α-glucosidase, β- glucosidase, in vivo hypoglycemic activity (one day and 15 days studies) in addition to PPARγ activation study. Four compounds (12c, 12f, 13b and 13f) had higher COX-2 S.I. (8.69–9.26) than the COX-2 selective drug celecoxib (COX-2 S.I. = 8.60) and showed the highest AI activities and the lowest ulcerogenicity than other derivatives. Also, two thiazolidindione derivatives 12e and 12f and two thiazolidinone derivatives 13b and 13c showed higher inhibitory activities against α- and β-glucosidase (% inhibitory activity = 62.15, 55.30, 65.37, 59.08 for α-glucosidase and 57.42, 60.07, 58.19, 66.90 for β-glucosidase respectively) than reference compounds (acarbose with % inhibitory activity = 49.50 for α-glucosidase and d-saccharic acid 1,4-lactone monohydrate with % inhibitory activity = 53.42 for β-glucosidase) and also showed good PPAR-γ activation and good hypoglycemic effect in comparison to pioglitazone and rosiglitazone. Moreover, Shape comparison and docking studies were carried out to understand their interaction and similarity with standard drugs.     

Reactions of ‘GaI’ with organometallic transition metal halides

Two approaches towards the synthesis of phosphine ligated half-sandwich complexes [(η^x-C_xH_x)M(PR₃)₂GaI₂]_n containing diiodogallyl ligands have been investigated. Insertion of ‘GaI’ into the Mo-I bond of (η⁷-C₇H₇)Mo(CO)₂I has been shown to yield the crystallographically characterized dimeric complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂ (2). Attempts to substitute the carbonyl ligands by the phosphine ligand dppe [dppe = bis(diphenylphosphino)ethane] have been shown instead to yield the sparingly soluble complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂(μ-dppe) (3) in which the phosphine bridges two [(η⁷-C₇H₇)Mo(CO)₂GaI₂] units via a pair of P → Ga donor/acceptor bonds. By contrast, attempts to insert ‘GaI’ directly into the metal-halogen bond of phosphine ligated complexes such as (η⁵-C₅H₅)Ru(PPh₃)₂Cl or (η⁵-C₅H₅)Ru(dppe)Cl have been shown to result in the formation of the tetraiodogallate species(η⁵-C₅H₅)Ru(PPh₃)₂(μ-I)GaI₃ (5) and [(η⁵-C₅H₅)Ru(dppe)]⁺[GaI₄]⁻ (7).     

New arene ruthenium complexes with planar chirality

1,2,4-Trimethyl-cyclohexadiene reacts with RuCl₃ · nH₂O in refluxing ethanol to afford quantitatively [RuCl₂(1,2,4-C₆H₃Me₃)]₂ (1), the coordination of 1,2,4-trimethylbenzene to the ruthenium atom introducing planar chirality at the η⁶-arene ligand. The dinuclear complex 1 reacts with two equivalents of triphenylphosphine (PPh₃) to give quantitatively, as a racemic mixture of enantiomers, [RuCl₂(1,2,4-C₆H₃Me₃)(PPh₃)] (2), the structure of which has been determined by a single-crystal X-ray structure analysis of (rac)-2. Similarly, 1 reacts with two equivalents of the enantiopure phosphine (1S,2S,5R)-(+)-neomenthyldiphenylphosphine (nmdpp) to afford in good yield [RuCl₂(1,2,4-C₆H₃Me₃)(nmdpp)] (3) as a mixture of diastereoisomers, from which the isomer 3a was isolated by crystallisation. A single-crystal X-ray structure analysis of 3a allowed the determination of the absolute configuration at the planar chiral η⁶-arene moiety. Finally, complex 1 reacts with one equivalent of the diphosphine ligand 1,1^′-bis(diphenylphosphino)ferrocene (dppfc) to give the heteronuclear complex [RuCl₂(1,2,4-C₆H₃Me₃) (dppfc)RuCl₂(1,2,4-C₆H₃Me₃)] (4). All complexes were fully characterised by elemental analysis, mass spectrometry, NMR and IR spectroscopies.     

Novel benzothiazole hydrazine carboxamide hybrid scaffolds as potential in vitro GABA AT enzyme inhibitors: Synthesis,molecular docking and antiepileptic evaluation

In the present study, a series of newer benzothiazole derivatives containing thiazolidin-4-one (5a-g) and azetidin-2-one (6a-g), were synthesized by the cyclization of benzothiazolyl arylidene hydrazine carboxamide derivatives with thioglycolic acid and chloroacetyl chloride, respectively. Results of in vivo anticonvulsant screening revealed that compounds having 2,4-dicholoro (5c and 6c) and 4-nitro substituent (5g) at the phenyl ring have promising anticonvulsant activities without any neurotoxicity. Selected compounds were also evaluated for their in vitro GABA AT inhibition. The results indicated that compound 5c (IC₅₀ 15.26 μM) exhibited excellent activity as compared to the standard drug vigabatrin (IC₅₀ 39.72 μM) suggesting the potential of these benzothiazole analogues as new anticonvulsant agents.