2-(1-(Dimethylamino)ethyl)phenylpalladium(II) complexes 5-functionalized with fluorous silyl tails

New fluorous-organometallics based on the chiral ligand α-methyl-N,N-dimethylbenzylamine (TMBA) were prepared by treatment of fluorous silyl bromide reagents with in situ 4-lithiated TMBA to give fluorous N,N-dimethyl(α-methyl-4-trialkylsilylbenzyl)amine ligands 1a-1c that vary in the number of fluorous tails attached to the Si atom. Ligands 1a-1c were successfully cyclo-palladated by treatment with Pd(OAc)₂/LiCl in methanol to furnish the corresponding chloride-bridged dimeric arylpalladium(II) complexes 2a-2c in good yields. The latter derivatives could be converted into monomeric Lewis-base adducts by complexation with pyridine (3a-3c), or triphenylphosphine (4a-4c). The crystal structure of triphenylphosphine complex 4a has been elucidated. To probe their fluorophilicity, the partition coefficient of each of the derivatives in the fluorous biphasic solvent (FBS) system perfluoromethylcyclohexane/n-octane has been determined.     

Synthesis and antitumor activity of 5-[1-(3-(dimethylamino)propyl)-5-halogenated-2-oxoindolin-(3Z)-ylidenemethyl]-2,4-dimethyl-1H-pyrrole-3-carboxamides

We report herein the design and synthesis of novel 1-[3-(dimethylamino)propyl]indolin-2-one derivatives based on the structural features of Sunitinib, a known multitargeted receptor tyrosine kinase inhibitor, and TMP-20, a previously discovered compound with good antitumor activity in our lab. These newly synthesized derivatives were evaluated for in vitro activity against five human cancer cell lines and VEGF/bFGF-stimulated HUVECs. Results revealed that all of the target compounds 1a-p show potent antitumor activity, compounds 1e-h (IC₅₀’s: 0.45-5.08 μM) are more active than Sunitinib (IC₅₀’s: 1.35-6.61 μM), and the most active compound 1h (IC₅₀: 0.47-3.11 μM) is 2.1-4.6-fold more potent than Sunitinib against all five cancer cell lines. In addition, like Sunitinib, 1a-p have higher selectivity on VEGF-stimulated HUVEC other than bFGF-stimulated HUVEC.     

Synthesis and antiviral activity of cyclopropyl-spirocarbocyclic adenosine, (4R,5S,6R,7R)-4-(6-amino-9H-purin-9-yl)-7-(hydroxymethyl)spiro[2.4]heptane-5,6-diol against hepatitis C virus

An efficient method was developed for the synthesis of 6-exocyclic methylene carbocyclic intermediate 4. The Simmons-Smith cyclopropanation protocol was applied on the 6-exocyclic methylene of intermediate 4 and demonstrated its utility for the synthesis of novel class of a spiro-carbocyclic nucleoside analog 8. The titled compound 8 demonstrated a significant antiviral activity against HCV with EC₅₀ values of 0.273 and 0.368 μM in genotypes 1A and 1B, respectively.     

Antitumor agents 279. Structure-activity relationship and in vivo studies of novel 2-(furan-2-yl)naphthalen-1-ol (FNO) analogs as potent and selective anti-breast cancer agents

In our ongoing modification study of neo-tanshinlactone (1), we discovered 2-(furan-2-yl)naphthalen-1-ol (FNO) derivatives 3 and 4 as a new class of anti-tumor agents. To explore structure-activity relationships (SAR) of this scaffold, 18 new analogs, 6-12 and 14-24, were designed and synthesized. The C11-esters 7 and 12 displayed broad anti-tumor activity (ED₅₀ 1.1-4.3 μg/mL against seven cancer cell lines), while C11-hydroxymethyl 14 showed unique selectivity against the SKBR-3 breast cancer cell line (ED₅₀ 0.73 μg/mL). Compounds 15 and 22 displayed potent and selective anti-breast tumor activity (ED₅₀ 1.7 and 0.85 μg/mL, respectively, against MDA-MB-231). The SAR results demonstrated that the substitutions from the ring-opened lactone ring C of 1 are critical to the anti-tumor potency as well as the apparent tumor-tissue type selectivity. Treatment with 3 in Brca1^f11/f11p53^f5&6/f5&6Cre^c mice models significantly inhibited the proliferation of mammary epithelial cells and branching of mammary glands.     

Facile route for the synthesis of the iminosugar nucleoside (3R,4R)-1-(pyren-1-yl)-4-(hydroxymethyl)pyrrolidin-3-ol

N-(Pyren-1-yl)-(3R,4S)-4-[(1S,2R)-1,2,3-trihydroxypropyl]pyrrolidin-3-ol (4) was obtained in 36% yield from 3-deoxy-3-C-formyl-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (3) by combined hydrolysis and aminoalkylation reactions with 1-aminopyrene in a one-pot reaction. Cleavage reactions of the exocyclic triol chain in 4 with NaIO₄ and NaBH₄ resulted in iminosugars 7 and 8, which are analogues of the furanose forms of 2-deoxy-d-allose and of 2-deoxy-d-ribose, the latter analogue N-(pyren-1-yl)-(3R,4R)-4-(hydroxymethyl)pyrrolidin-3-ol (8) being formed in 83% yield.     

1-((3S,4S)-4-amino-1-(4-substituted-1,3,5-triazin-2-yl) pyrrolidin-3-yl)-5,5-difluoropiperidin-2-one inhibitors of DPP-4 for the treatment of type 2 diabetes

A 3-amino-4-substituted pyrrolidine series of dipeptidyl peptidase IV (DPP-4) inhibitors was rapidly developed into a candidate series by identification of a polar valerolactam replacement for the lipophilic 2,4,5-trifluorophenyl pharmacophore. The addition of a gem-difluoro substituent to the lactam improved overall DPP-4 inhibition and an efficient asymmetric route to 3,4-diaminopyrrolidines was developed. Advanced profiling of a subset of analogs identified 5o with an acceptable human DPP-4 inhibition profile based on a rat PK/PD model and a projected human dose that was suitable for clinical development.     

Synthesis, characterization and ethylene oligomerization behavior of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridylnickel dihalides

A series of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (L1-L6) was synthesized and fully characterized. They reacted with NiCl₂ or (DME)NiBr₂ to form the corresponding N^N^N tridentate nickel dichlorides (C1-C6) or dibromides (C7-C12). All nickel complexes were characterized by elemental analysis and infrared spectroscopy, while the X-ray diffraction study reveals the distorted octahedral geometry of representative nickel dichloride complex C3 and nickel dibromide complex C7. All nickel complexes, activated with either Et₃Al₂Cl₃ or Et₂AlCl, showed good activities in ethylene oligomerization, and notably remarkably high selectivity of α-olefins was achieved in the presence of Et₃Al₂Cl₃. The chloro-substituted ligands enhanced the activities of complexes in ethylene polymerization.     

Antitumor agents 287. Substituted 4-amino-2H-pyran-2-one (APO) analogs reveal a new scaffold from neo-tanshinlactone with in vitro anticancer activity

4-Amino-2H-benzo[h]chromen-2-one (ABO) and 4-amino-7,8,9,10-tetrahydro-2H-benzo[h]chromen-2-one (ATBO) analogs were found to be significant in vitro anticancer agents in our previous research. Our continuing study has now discovered a new simplified (monocyclic rather than tricyclic) class of cytotoxic agents, 4-amino-2H-pyran-2-one (APO) analogs. By incorporating various substituents on the pyranone ring, we have established preliminary structure-activity relationships (SAR). Analogs 19, 20, 23, and 26-30 displayed significant tumor cell growth inhibitory activity in vitro. The most active compound 27 exhibited ED₅₀ values of 0.059-0.090 μM.     

Molecular basis of the interaction of novel tributyltin(IV) 2/4-[(E)-2-(aryl)-1-diazenyl]benzoates endowed with an improved cytotoxic profile: Synthesis, structure, biological efficacy and QSAR studies

A series of tributyltin(IV) complexes based on 2/4-[(E)-2-(aryl)-1-diazenyl]benzoate ligands was synthesized, wherein the position of the carboxylate and aryl substituents (methyl, tert-butyl and hydroxyl) varies. The complexes, Bu₃SnL^1-4H (1-4), have been structurally characterized by elemental analysis and IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) and ¹¹⁹Sn Mössbauer spectroscopy. All have a tetrahedral geometry in solution and a trigonal bipyramidal geometry in the solid-state, except for Bu₃SnL⁴H (4) that was ascertained to have tetrahedral coordination by X-ray crystallography. Cytotoxicity studies were carried out on human tumor cell lines A498 (renal cancer), EVSA-T (mammary cancer), H226 (non-small-cell lung cancer), IGROV (ovarian cancer), M19 MEL (melanoma), MCF-7 (mammary cancer) and WIDR (colon cancer). Compared to cisplatin, test compounds 1-4 had remarkably good activity, despite the presence of substantial steric bulk due to Sn-Bu ligands. The quantitative structure-activity relationship (QSAR) studies for the cytotoxicity of organotin(IV) benzoates, along with some reference drug molecules, is also discussed against a panel of human tumor cell lines. Molecular structures of the tributyltin(IV) complexes (1-4) were fully optimized using the PM6 semi-empirical method and docking studies performed with key enzymes associated with the propagation of cancer, namely ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II. The theoretical results are discussed in relation to the mechanistic role of the cytotoxic active test compounds (1-4).     

Reactivity of the ligand bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ether (L1) with Pd(II) and Pt(II): crystal structure of cis-[PtCl2(L1)]

The coordination chemistry of the ligand bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ether (L₁) was tested in front of Pd(II) and Pt(II). Complexes cis-[MCl₂(L₁)] (M=Pd(II) and Pt(II)) were obtained, due to the chelate condition of the ligand and the formation of a stable 10-membered ring. The crystal structure of cis-[PtCl₂(L₁)] was resolved by X-ray diffraction. Treatment of [PdCl₂(L₁)] or [Pd(CH₃CN)₄](BF₄)₂ with AgBF₄ in the presence of L₁ gave the complex [Pd(L₁)₂](BF₄)₂. The initial cis-[PdCl₂(L₁)] was recovered by reacting [Pd(L₁)₂](BF₄)₂ with an excess of NEt₄Cl. Reaction of [Pt(CH₃CN)₄](BF₄)₂ (generated in situ from [PtCl₂(CH₃CN)₂] and AgBF₄ in acetonitrile) with ligand L₁ yields complex [Pt(L₁)₂](BF₄)₂.     

Synthesis and structural characterization of Pd(II) complexes containing 2,6-bis[(dimethylamino)methyl]-4-methylphenolate ligand

Treatment of 2,6-bis[(dimethylamino)methyl]-4-methylphenol (1) with [Pd(PhCN)₂Cl₂] in a 1:1 molar ratio gives the mononuclear Pd(II) complex [PdCl₂(OC₆H₂(CH₂NMe₂)-2-Me-4-(CH₂NHMe₂)-6)] (2) containing one ligand with an ammonium hydrogen atom, which forms a bifurcated hydrogen bonding to the phenoxy oxygen and the chlorine atoms, as shown by the single crystal X-ray diffraction study. The reaction between the lithium salt of 1 and [Pd(COD)Cl₂] gives the mononuclear Pd(II) complex [Pd(OC₆H₂(CH₂NMe₂)₂-2,6-Me-4)₂] (3). The X-ray structure of 3 showed the presence of two ligands coordinated to one palladium metal center in a trans fashion with two dangling dimethylamine groups. The yield of the complex 3 was improved by carrying out the reaction between [Pd(OAc)₂] and 1 in acetone. The solid state structures of the complexes 2 and 3 were confirmed by ¹H, ¹³C, HETCOR NMR, IR and elemental analysis methods. The ¹H NMR spectra of 2 and 3 showed two different chemical shifts corresponding to the coordinated and uncoordinated amine groups of the ligand. No decoalescence of signals for the chelate ring puckering process was observed in variable-temperature NMR spectra.     

Rhenium tricarbonyl complexes of 1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazoles

Copper(I) catalyzed [3+2] cycloaddition reactions between 5-ethynylbipyridine and benzyl, p-methylbenzyl, or m-bromobenzyl azides yields the corresponding 1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazoles 1-3. Reaction between 1-3 and [NEt₄]₂[Re(CO)₃Br₃] yields the [1-benzyl-4-(5-bipyridyl)-1H-1,2,3-triazole]Re(CO)₃Br complexes 4-6. The Re(CO)₃Br complexes of 5- and 6-ethynylbipyridine complexes (7-8) are prepared in a similar fashion. Cycloaddition reactions between 7 and benzyl azide yields mixtures of 4 and unreacted starting material.     

Triorganotin(IV) complexes of Schiff base derived from 6-amino-2-mercaptobenzothiazole: Synthesis, characterization and X-ray crystal structures

Nine triorganotin(IV) complexes of the type R₃SnL (L = L1 R = Me 1, Ph 2, PhCH₂3; L = L2 R = Me 4, Ph 5, PhCH₂6; L = L2 R = Me 7, Ph 8, PhCH₂9) have been obtained by reaction of new Schiff base HL1, HL2 or HL3 with triorganotin(IV) chloride in the presence of sodium ethoxide. All the complexes 1-9 were characterized by elemental, IR and NMR spectra analyses. Except for complexes 3, 4, 6, 9, the others were also characterized by X-ray crystallography diffraction analyses, which revealed that complexes 1, 2, 5, 7, 8 were four coordinated and displayed a capped tetrahedron.     

Zinc(II) complexes of 2-acetyl pyridine 1-(4-fluorophenyl)-piperazinyl thiosemicarbazone: Synthesis, spectroscopic study and crystal structures - Potential anticancer drugs

2-Acetyl pyridine thiosemicarbazone containing an 1-(4-fluorophenyl)-piperazinyl ring incorporated at N(4)-position, HAcPipPheF (1) and the zinc(II) complexes [Zn(AcPipPheF)₂] (2) and [Zn(OAc)(AcPipPheF)]₂ (3) have been prepared and structurally characterized by means of vibrational and NMR (¹H and ¹³C) spectroscopy. The crystal structures of the compounds 1-3 have been determined by X-ray crystallography. The metal coordination geometry of [Zn(AcPipPheF)₂] is described as distorted octahedral configuration in a trans-N-cis-N-cis-S configuration. In [Zn(OAc)(AcPipPheF)]₂ one of the acetato group exhibits monoatomic bridge and the other bridges in a bidentate manner. The zinc(1) metal ion is coordinated in a distorted octahedral configuration while the metal coordination of Zn(2) is described as distorted square pyramidal. Biomedical studies revealed that, compounds 1-3 displayed potent anticancer activity. The antiproliferative activity of 1-3 was found to be considerably stronger than that of cis-platin. The IC₅₀ values range from 26 to 90 nM, against all cell lines tested, while for cis-platin the IC₅₀ values range from 2 to 17 μM and for the zinc salt, ZnCl₂, the IC₅₀ values range from 81 to 93 μM. The complex 3 shows the highest activity against all four cancer cell lines and the highest selectivity against K562 and MDA-MB-453 cancer cell lines. The compounds inhibited tumor cell proliferation by arresting the cell cycle progression at the S phase.     

Regioselectivity in the glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol

The glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol (1) and its 3-benzylsulfanyl and 3-methylsulfanyl derivatives with different glycosyl halides 2-4 has been studied in presence of base. The S-glycosides 5-7 were obtained in the presence of triethylamine, whereas the respective S,N⁴-bis(glycosyl) derivatives 8-10 were synthesized in the presence of potassium carbonate; the S,N²-bis(glycosyl) isomer 11 could also be isolated in the case of the galactosyl analog. Similarly, after protecting 1 as 3-benzyl(methyl)sulfanyl derivatives 12 or 13, the N⁴-glycosyl analogs 14-19 as well as minor amounts of S,N²-bis(galactosyl) isomers 20 and 21 were formed. The theoretical calculations using AM1 semiempirical methods agreed with the experimental results. Microwave irradiation (MWI) led to higher yields in much less time than the conventional methods, and no change in regioselectivity has been noticed.     

Synthesis, crystal structures and characterization of three novel complexes with N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand

Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H₂L). Three novel complexes constructed from H₂L, namely, [M(HL)₂] · xH₂O (M = Cu, x = 0 for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3) have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, X-ray powder diffraction (XRPD), FT-IR, UV-Vis, TGA and photoluminescence measurements. Complex hydrogen bonds, C-H···π and π-π stacking interactions lead 1-3 to present 1-D, 2-D and 3-D supramolecular architectures, respectively.     

Synthesis and evaluation of 6-[1-(2-[(18)F]fluoro-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline for positron emission tomography imaging of the metabotropic glutamate receptor type 1 in brain

The purpose of this study was to synthesize 6-[1-(2-[¹⁸F]fluoro-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline ([¹⁸F]FPTQ, [¹⁸F]7a) and to evaluate its potential as a positron emission tomography ligand for imaging metabotropic glutamate receptor type 1 (mGluR1) in the rat brain. Compound [¹⁸F]7a was synthesized by [¹⁸F]fluorination of 6-[1-(2-bromo-3-pyridyl)-5-methyl-1H-1,2,3-triazol-4-yl]quinoline (7b) with potassium [¹⁸F]fluoride. At the end of synthesis, 1280-1830 MBq (n = 8) of [¹⁸F]7a was obtained with >98% radiochemical purity and 118-237 GBq/??mol specific activity using 3300-4000 MBq of [¹⁸F]F⁻. In vitro autoradiography showed that [¹⁸F]7a had high specific binding with mGluR1 in the rat brain. Biodistribution study using a dissection method and small-animal PET showed that [¹⁸F]7a had high uptake in the rat brain. The uptake of radioactivity in the cerebellum was reduced by unlabeled 7a and mGluR1-selective ligand JNJ-16259685 (2), indicating that [¹⁸F]7a had in vivo specific binding with mGluR1. Because of a low amount of radiolabeled metabolite present in the brain, [¹⁸F]7a may have a limiting potential for the in vivo imaging of mGluR1 by PET.     

Reactions of hybrid organotellurium ligands 1-(4-methoxyphenyl telluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L) and 1-ethylthio-2-[2-thienyltelluro]ethane (L) with mercury (II) bromide: formation of complexes and their decomposition

Two tellurium ligands 1-(4-methoxyphenyltelluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L¹) and 1-ethylthio-2-[2-thienyltelluro]ethane (L²) have been synthesized by reacting nucleophiles [4-MeO-C₆H₄Te⁻] and [C₄H₃S-2-Te⁻] with 2-[3-(6-methyl-2-pyridyl)propoxy]ethylchloride and chloroethyl ethyl sulfide, respectively. Both the ligands react with HgBr₂ resulting in complexes of stoichiometry [HgBr₂ · L¹/L²] (1/4), which show characteristic NMR (¹H and ¹³C{¹H}). On crystallization of 1 from acetone-hexane (2:1) mixture, the cleavage of L¹ occurs resulting in 4-MeOC₆H₄HgBr (2) and [RTe⁺→HgBr₂]Br⁻ (3) (where R = -CH₂CH₂OCH₂CH₂CH₂-(2-(6-CH₃-C₅H₃N))). The 2 is characterized by X-ray diffraction on its single crystal. It is a linear molecule and is the first such system which is fully characterized structurally. The Hg-C and Hg-Br bond lengths are 2.085(6) and2.4700(7) Å. The distance of four bromine atoms (3.4041(7)-3.546(7) Å) around Hg (cis to C) is greater than the sum of van der Waal’s radii 3.30 Å. This mercury promoted cleavage is observed for an acyclic ligand of RArTe type for the first time and is unique, as there appears to be no strong intramolecular interaction to stabilize the cleavage products. The 4 on crystallization shows the cleavage of organotellurium ligand L² and formation of a unique complex [(EtS(CH₂)₂SEt)HgBr(μ-Br)Hg(Br)(μ-Br)₂Hg(Br)(μ-Br)BrHg(EtS(CH₂)₂SEt)] · 2HgBr₂ (5), which has been characterized by single crystal structure determination and ¹H and ¹³C{¹H} NMR spectra. The elemental tellurium and [C₄H₃SCH₂]₂ are the other products of dissociation as identified by NMR (proton and carbon-13). The cleavage appears to be without any transmetalation and probably first of its kind. The centrosymmetric structure of 5 is unique as it has [HgBr₃]⁻ unit, one Hg in distorted tetrahedral geometry and one in pseudo-trigonal bipyramidal one. The molecule of 5 may also be described as having [(EtSCH₂CH₂SEt)HgBr]⁺ [HgBr₃]⁻ units, which dimerize and co-crystallize with two HgBr₂ moieties. There are very weak Hg?Br interactions between co-crystallized HgBr₂ units and rest of the molecule. [Hg(3)-Br(1)/Hg(3)-Br(4) = 3.148(1)/3.216(1) Å]. The bridging Hg?Br distances, Hg(2)-Br(4)′, Hg(2)′-Br(4) and Hg(1)-Br(2), are from 2.914(1) to 3.008(1) Å.     

Synthesis, photophysical and photochemical properties of novel soluble tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato zinc(II) and Ti(IV)O complexes

The synthesis, photophysical and photochemical properties of zinc and oxo-titanium phthalocyanine derivatives 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)zinc(II), (2); and 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)oxo-titanium(IV), (3), are described for the first time. These peripherally substituted complexes (2 and 3) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and electronic spectroscopy. The compounds (2 and 3) have good solubility in organic solvents such as CHCl₃, DCM, DMSO, DMF, THF and toluene and are not aggregated within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO, DMF and THF. Compound 2 has higher fluorescence quantum yields, triplet quantum yields and triplet life times than 3, however, the former has lower singlet oxygen quantum yields and photodegradation quantum yields than the latter.     

Discovery of β-aminoacyl containing thiazolidine derivatives as potent and selective dipeptidyl peptidase IV inhibitors

A series of β-aminoacyl containing thiazolidine derivatives was synthesized and evaluated for their ability to inhibit DPP-IV. Several thiazolidine derivatives with an acid moiety were found to be potent DPP-IV inhibitors. Among them, compound 2da is the most active in this series with an IC₅₀ value of 1 nM, and it showed excellent selectivity over DPP-IV related enzymes including DPP-2, DPP-8, and DPP-9. Compound 2da is chemically and metabolically stable, and showed no CYP inhibition, hERG binding or cytotoxicity. Compound 2db, an ester prodrug of 2da, showed good in vivo DPP-IV inhibition after oral administration in rat and dog models.