Pterocarpans and isoflavones from the root bark of Millettia micans and of Millettia dura

From the CH₂Cl₂/CH₃OH (1:1) extract of the root bark of Millettia micans, a new pterocarpan, (6aR,11aR)-3-hydroxy-7,8,9-trimethoxypterocarpan (1), named micanspterocarpan, was isolated. Similar investigation of the CH₂Cl₂/CH₃OH (1:1) extract of the root bark of Millettia dura gave a further new pterocarpan, (6aR,11aR)-8,9-methylenedioxy-3-prenyloxypterocarpan (2), named 3-O-prenylmaackiain, along with six known isoflavones (3-8) and a chalcone (9). All purified compounds were identified by NMR and MS, whereas the absolute configurations of the new pterocarpans were established by chriptical data analyses including quantum chemical ECD calculation. Among the isolated constituents, calopogonium isoflavone B (3) and isoerythrin A-4′-(3-methylbut-2-enyl) ether (4) showed marginal activities against the 3D7 and the Dd2 strains of Plasmodium falciparum (70–90% inhibition at 40 μM). Maximaisoflavone B (5) and 7,2′-dimethoxy-4′,5′-methylenedioxyisoflavone (7) were weakly cytotoxic (IC₅₀ 153.5 and 174.1 μM, respectively) against the MDA-MB-231 human breast cancer cell line. None of the tested compounds showed in-vitro translation inhibitory activity or toxicity against the HEK-293 human embryonic kidney cell line at 40 μM.     

Inductive influence of 4′-terpyridyl substituents on redox and spin state properties of iron(II) and cobalt(II) bis-terpyridyl complexes

A series of iron and cobalt bis-terpyridine (terpy) complexes were prepared with the general formula [M(R-terpy)₂](PF₆)₂, where M represents Co(II) and Fe(II), and R is the following terpyridine substituents in order of increasing electron-withdrawing behavior [(C₄H₈)N, (C₄H₉)NH, HO, CH₃O, CH₃-phenyl, H, Cl, CH₃SO, CH₃SO₂]. The complexes were prepared to investigate the extent of redox and spin state control that is attainable by simply varying the electron donating/withdrawing influence using a single substituent site on the terpyridine ligand. Cyclic voltammetry was used to assess the substituents influence on the M(III/II) redox couple. A plot of the M(III/II) redox potential (E_1/2) versus the electron donating/withdrawing nature of the substituents (Hammett constants), shows a strong linear trend for both metals; however, the substituents were observed to have a stronger influence on the Fe(III/II) couple. Solution magnetic susceptibility measurements at room temperature were carried out using standard NMR methodology (modified Evans method) where all of the Fe(II) complexes exhibited a diamagnetic, low spin (S = 0) behavior. In the cobalt series where R = H for [Co(R-terpy)₂]²⁺, the complex is known to be near the spin cross-over where the room temperature effective magnetic moment (μ_eff) in solution is ≈3.1 Bohr magnetons; however, in this study the μ_eff is observed to vary between 2.7 and 4.1 Bohr magnetons depending on the R-substituent.     

Natural ortho-dihydroxyisoflavone derivatives from aged Korean fermented soybean paste as potent tyrosinase and melanin formation inhibitors

Natural o-dihydroxyisoflavone (ODI) derivatives with variable hydroxyl substituent at the aromatic ring of isoflavone and three known isoflavones were isolated from five-year-old Korean fermented soybean paste (Doenjang) and evaluated as potent inhibitors on tyrosinase activity and melanin formation in melan-a cells comparing with other known isoflavones, 7,8,4′-trihydroxyisoflavone (1) and 7,3′,4′-trihydroxyisoflavone (2) inhibited tyrosinase by 50% at a concentration of 11.21 ± 0.8 μM and 5.23 ± 0.6 μM (IC₅₀), respectively, whereas, 6,7,4′-trihydroxyisoflavone (3), daidzein (4), glycitein (5) and genistein (6) showed very low inhibition activity. Furthermore, those compounds significantly suppressed the cellular melanin formation by 50% at a concentration of 12.23 ± 0.7 μM (1), 7.83 ± 0.7 μM (2), and 57.83 ± 0.5(6) and show more activity than arbutin. But, compounds 3, 4, and 5 showed lower inhibition activity. This study shows that the position of hydroxyl substituent at the aromatic ring of isoflavone plays an important role in the intracellular regulation of melanin formation in cell-based assay system.     

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,5′-dihydro-1′,3′-oxazole 1 and 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,4′-dimethyl-4′,5′-dihydro-1′,3′-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λ_max = 422 nm, λ_min = 386 nm) and compound 2 (λ_max = 416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC₅₀ = 0.9 ± 0.1 μM, and IC₅₀ = 1.3 ± 0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC₅₀ = 13 ± 1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4′-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4′,4′-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.     

Design and synthesis of N6-substituted-4′-thioadenosine-5′-uronamides as potent and selective human A3 adenosine receptor agonists

On the basis of a bioisosteric rationale, 4′-thionucleoside analogues of IB-MECA (N⁶-(3-Iodo-benzyl)-9-(5′-methylaminocarbonyl-β-d-ribofuranosyl)adenine), which is a potent and selective A₃ adenosine receptor (AR) agonist, were synthesized from d-gulonic acid γ-lactone. The 4′-thio analogue (5h) of IB-MECA showed extremely high binding affinity (K_i = 0.25 nM) at the human A₃AR and was more potent than IB-MECA (K_i = 1.4 nM). Bulky substituents at the 5′-uronamide position, such as cyclohexyl and 2-methylbenzyl, in this series of 2-H nucleoside derivatives were tolerated in A₃AR binding, although small alkyl analogues were more potent.     

Syntheses,structures, and magnetic properties of heterobimetallic complexes based on tetracyanometallic building blocks

Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)₄]^? (2) and [Fe(4,4′-dmbipy)(CN)₄]^? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu₂(bpca)₂(H₂O)₂Fe₂(5,5′-dmbipy)₂(CN)₈] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)₄] · 4H₂O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)₄]_n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J₁ = 2.64 cm^?1, J₂ = 5.40 cm^?1 and TIP = ?2.36 × 10^?3 for complex 4, and g = 2.17, J = 4.82 cm^?1 and zJ′ = 0.029 cm^?1 for complex 5.     

Structure–cytotoxic activity relationship of sesquilignan,morinol A

The cytotoxic activities of sesquilignans, (7S,8S,7′R,8′R)- and (7R,8R,7′S,8′S)-morinol A and (7S,8S,7′S,8′S)- and (7R,8R,7′R,8′R)-morinol B were compared, showing no significant difference between stereoisomers (IC₅₀ = 24–35 μM). As a next stage, the effect of substituents at 7, 7′, and 7″-aromatic ring on the activity was evaluated to find out the higher activity of (7S,8S,7′R,8′R)-7,7′,7″-phenyl derivative 18 (IC₅₀ = 6–7 μM). In the research on the structure–activity relationship of 7″-position of (7S,8S,7′R,8′R)-7,7′,7″-phenyl derivative 18, the most potent compounds were 7,7′,7″-phenyl derivative 18 (IC₅₀ = 6 μM) against HeLa cells. Against HL-60 cells, 7″-(4-nitrophenyl)-7,7′-phenyl derivative 33 and 7″-hexyl-7,7′-phenyl derivative 37 (IC₅₀ = 5 μM) showed highest activity. We discovered the compounds showed four to sevenfold potent activity than that of natural (7S,8S,7′R,8′R)-morinol A. It was also confirmed that the 7′-benzylic hydroxy group have an important role for exhibiting activity, on the other hand, the resonance system of cinnamyl structure is not crucial for the potent activity.     

Linear homobimetallic 4-thioacetyl-substituted NCN pincer palladium(II) and platinum(II) complexes with N-bidentate connecting units (NCN = [C6H2(CH2NMe2)2-2,6-R-4]−)

The synthesis and characterization of homobimetallic palladium and platinum complexes of type [(Me(O)CS-4-NCN–M ← N^∩N → M–NCN-4-SC(O)Me](OTf)₂ (Me(O)CS-4-NCN = [C₆H₂(CH₂NMe₂)₂-2,6-SC(O)Me-4]^?; N^∩N = 4,4′-bipyridine (bipy); M = Pd, 12; M = Pt, 13) is reported. The required bifunctional thio-acetyl NCN pincer starting compound NC(Br)N-4-SC(O)Me (2) has been synthesized by the consecutive reactions of NC(Br)N–I (I-1-C₆H₂(CH₂NMe₂)₂-3,5-Br-4) (1) with ^tBuLi, S₈ and Me(O)CCl, respectively. Chemoselective metallation at the C_aryl–Br bond was achieved by the reaction of 2 with the palladium(0) source [Pd₂(dba)₃] (3) (dba = dibenzylidene acetone). Treatment of thus formed [Pd(NCN-4-SC(O)Me)(Br)] (4) with [AgOTf] (8) (OTf = triflate, OSO₂CF₃) gave [Pd(NCN-4-SC(O)Me)(H₂O)][OTf] (9) which was further reacted with 0.5 equiv. of 4,4′-bipyridine (11a) to afford rigid-rod structured 12. When [Pt(tol)₂(SEt₂)]₂ (5) (tol = 4-tolyl) was used instead of 3, then 13 was produced via the in situ formation of [PtBr(NCN-4-SC(O)Me)] (7) and [Pt(NCN-4-SC(O)Me)(H₂O)][OTf] (10). Another possibility to synthesize 7 relied upon the subsequent reaction of 1 with 0.5 equiv. of 5 to give [PtBr(NCN-4-I)] (6) which further reacted with ^tBuLi, 1/8 S₈ and Me(O)CCl to afford 7. The cyclic voltammograms of 2, 7, and 13 are discussed.Complex 7 was structurally characterized by single crystal X-ray crystallography. Organometallic 7 crystallizes with three independent molecules in the asymmetric unit and displays a monomeric structure as commonly encountered in d⁸-metal pincer chemistry.     

Comparing anti-HIV,antibacterial, antifungal,micellar, and cytotoxic properties of tricarboxylato dendritic amphiphiles

Three series of homologous dendritic amphiphiles—RCONHC(CH₂CH₂COOH)₃, 1(n); ROCONHC(CH₂CH₂COOH)₃, 2(n); RNHCONHC(CH₂CH₂COOH)₃, 3(n), where R = n-C_nH_2n+1 and n = 13–22 carbon atoms—were assayed for their potential to serve as antimicrobial components in a topical vaginal formulation. Comparing epithelial cytotoxicities to the ability of these homologues to inhibit HIV, Neisseria gonorrhoeae, and Candida albicans provided a measure of their prophylactic/therapeutic potential. Measurements of the ability to inhibit Lactobacillus plantarum, a beneficial bacterium in the vagina, and critical micelle concentrations (CMCs), an indicator of the potential detergency of these amphiphiles, provided additional assessments of safety. Several amphiphiles from each homologous series had modest anti-HIV activity (EC₅₀ = 110–130 μM). Amphiphile 2(18) had the best anti-Neisseria activity (MIC = 65 μM), while 1(19) and 1(21) had MICs against C. albicans of 16 and 7.7 μM, respectively. Two measures of safety showed promise as all compounds had relatively low cytotoxic activity (EC₅₀ = 210–940 μM) against epithelial cells and low activity against L. plantarum, 1(n), 2(n), and 3(n) had MICs ? 490, 1300, and 940 μM, respectively. CMCs measured in aqueous triethanolamine and in aqueous potassium hydroxide showed linear dependences on chain length. As expected, the longest chain in each series had the lowest CMC—in triethanolamine: 1(21), 1500 μM; 2(22), 320 μM; 3(22), 340 μM, and in potassium hydroxide: 1(21), 130 μM; 3(22), 40 μM. The CMC in triethanolamine adjusted to pH 7.4 was 400 μM for 1(21) and 3900 μM for 3(16). The promising antifungal activity, low activity against L. plantarum, relatively high CMCs, and modest epithelial cytotoxicity in addition to their anti-Neisseria properties warrant further design studies with dendritic amphiphiles to improve their safety indices to produce suitable candidates for antimicrobial vaginal products.     

Two new anti-HBV lignans from Herpetospermum caudigerum

Two new lignans, named (+)-(7′S, 7″S, 8′R, 8″R)-4, 4′, 4″-trihydroxy-3, 5′, 3″-trimethoxy-7-oxo-8-ene [8-3′, 7′-O-9″, 8′-8″, 9′-O-7″] lignoid (1) and (1S)-4-Hydroxy-3-[2-(4-hydroxy-3-methoxy-phenyl)-1-hydroxymethyl-2-oxo-ethyl]-5-methoxy-benzaldehyde (2), along with five known (3–7) ones, have been isolated from the 95% ethanol extract of the seeds of Herpetospermum caudigerum Wall. The structures of the new compounds, including the absolute configurations, were elucidated by spectroscopic and CD analysis. Compounds 1, 2, and 7 displayed inhibitory activities on HBsAg secretion with IC₅₀ values of 20.5, 0.34, and 4.89 μM, while 1, 2, and 7 displayed inhibitory activities on HBeAg secretion with IC₅₀ values of 3.54, 4.83 × 10⁻⁴, and 8.02 μM, and cytotoxicity on HepG 2.2.15 cells with CC₅₀ values of 12.7, 2.96 × 10⁵, and 11.4 μM, respectively.     

Expanding the 4,4′-bipyridine ligand: Structural variation in {M(pytpy)2}2+ complexes (pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine,M = Fe,Ni, Ru) and assembly of the hydrogen-bonded,one-dimensional polymer {[Ru(pytpy)(Hpytpy)]}n3n+

The solid state structures of [Ni(1)₂][NO₃]₂ · 2MeOH · 2H₂O, [Fe(1)₂][ClO₄]₂ · 2MeOH · 0.5H₂O, [Ru(1)₂][PF₆]₂ and [Ru(1)₂][PF₆][NO₃] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)₂}²⁺ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)₂]²⁺ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}_n]³ⁿ⁺ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)₆} · 1.25H₂O]_n.     

Synthesis and pharmacological evaluation of optically pure,novel carbonyl guanidine derivatives as dual 5-HT2B and 5-HT7 receptor antagonists

A series of 9-disubstituted N-(9H-fluorene-2-carbonyl)guanidine derivatives have been discovered as potent and orally active dual 5-HT_2B and 5-HT₇ receptor antagonists. Upon screening several compounds, N-(diaminomethylene)-4′,5′-dihydro-3′H-spiro[fluorene-9,2′-furan]-2-carboxamide (17) exhibited potent affinity for both 5-HT_2B (K_i = 5.1 nM) and 5-HT₇ (K_i = 1.7 nM) receptors with high selectivity over 5-HT_2A, 5-HT_2C, α₁, D₂ and M₁ receptors. Optical resolution of the intermediate carboxylic acid 16 via the formation of diastereomeric salts using chiral alkaloids gave the optically pure compounds (R)-17 and (S)-17. Both enantiomers suppressed 5-HT-induced dural protein extravasation in guinea pigs in a dose-dependent manner and the amount of leaked protein was suppressed to near normal levels when orally administrated at 10 mg/kg. (R)-17 and (S)-17 were therefore selected as candidates for human clinical trials.     

Dihydrochalcone glucosides and antioxidant activity from the roots of Anneslea fragrans var. lanceolata

Bioassay-guided fractionation of the roots of Anneslea fragrans var. lanceolata led to the isolation of four dihydrochalcone glucosides, davidigenin-2′-O-(6″-O-4″′-hydroxybenzoyl)-β-glucoside (1), davidigenin-2′-O-(2″-O-4″′-hydroxybenzoyl)-β-glucoside (2), davidigenin-2′-O-(3″-O-4″′-hydroxybenzoyl)-β-glucoside (3), and davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), and 13 known compounds. The structures were identified by means of spectroscopic analysis. Davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), 1-O-3,4-dimethoxy-5-hydroxyphenyl-6-O-(3,5-di-O-methylgalloyl)-β-glucopyranoside (5), lyoniresinol (10), and syringic acid (13) showed ABTS [2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] cation radical scavenging activity, with SC₅₀ values of 52.6 ± 5.5, 26.0 ± 0.7, 6.0 ± 0.2, and 27.5 ± 0.6 μg/mL in 20 min, respectively. Lyoniresinol (10), isofraxidin (12), and syringic acid (13) also showed DPPH [1,1-diphenyl-2-picrylhydrazyl] radical scavenging activity, with SC₅₀ values of 8.4 ± 1.8, 51.6 ± 2.2, and 4.3 ± 0.7 μg/mL in 30 min, respectively.     

Constituents of Nelumbo nucifera leaves and their antimalarial and antifungal activity

From the leaves of Nelumbo nucifera (an aquatic plant), one new compound, 24(R)-ethylcholest-6-ene-5α-ol-3-O-β-d-glucopyranoside (1), along with 11 known metabolites (2–12), were isolated and identified by spectroscopic methods including 1D- and 2D NMR. Antifungal activity for (R)-roemerine (3) (IC₅₀/MIC = 4.5/10 μg/mL against Candida albicans) and antimalarial activity for (R)-roemerine (3) and N-methylasimilobine (5) (IC₅₀ = 0.2 and 4.8 μg/mL for the D6 clone, respectively, and 0.4 and 4.8 μg/mL for the W2 clone, respectively) was observed. None of the compounds were cytotoxic to Vero cells up to a concentration of 23.8 μg/mL. NMR data for 10-eicosanol (7) and 7,11,15-trimethyl-2-hexadecanone (10) are presented for the first time. An analysis of the structure–activity relationship shows that the substituents in position C-1 and C-2 of aporphine alkaloids are crucial for the antimalarial activity.     

Redefining the structure–activity relationships of 2,6-methano-3-benzazocines. Part 8. High affinity ligands for opioid receptors in the picomolar Ki range: Oxygenated N-(2-[1,1′-biphenyl]-4-ylethyl) analogues of 8-CAC

N-[2-(4′-methoxy[1,1′-biphenyl]-4-yl)ethyl]-8-CAC (1) is a high affinity (K_i = 0.084 nM) ligand for the μ opioid receptor and served as the lead compound for this study. Analogues of 1 were made in hopes of identifying an SAR within a series of oxygenated (distal) phenyl derivatives. A number of new analogues were made having single-digit pM affinity for the μ receptor. The most potent was the 3′,4′-methylenedioxy analogue 18 (K_i = 1.6 pM).     

Photophysical studies of hetero-bischelated complexes of rhodium(III) containing 2,2′-dipyridylamine

Four mixed-ligand complexes, cis-Rh[(bipy)(HDPA)Cl₂]Cl (1), cis-[Rh(phen)(HDPA)Cl₂]Cl (2), cis-[Rh(bipy)(DPA)Cl₂] (3), and cis-[Rh(phen)(DPA)Cl₂] (4) (where bipy = 2,2′-bipyridine, phen = 1,10-phenantroline, HDPA = 2,2′-dipyridylamine, and DPA = the deprotonated form of 2,2′-dipyridylamine) have been synthesized and characterized. In slightly acidic solution and at low temperature (77 K), both complexes 1 and 2 show a broad, symmetric and structureless red emission with microsecond lifetime identified as dd* phosphorescence. In slightly basic solution, the deprotonated complexes (3 and 4) exhibit a broad and asymmetric blue emission, showing no vibrational structure with a lifetime in the order of microseconds. Emission of complex 3 reveals a blue shift of 0.81 μm⁻¹ compared to the emission of complex 1 and that of complex 4 shows a blue shift of 0.77 μm⁻¹ with respect to complex 2. Electrochemical data have also been obtained for the four complexes in CH₃CN. There are two reduction peaks observed for both complexes 1 and 2. Each peak is followed by a one-electron reduction at the metal, with an elimination of chloride during each reduction step, which is in consistent with the dd* phosphorescence assignment for the two complexes. For complexes 3 and 4, only a one-electron reduction process occurs at the metal with an elimination of chloride. Based on the luminescence and electrochemical data, the emission of complexes 3 and 4 are assigned as πd* phosphorescence. Results from density functional theory (DFT) calculations provide theoretical evidence in support of this πd* assignments.     

Ionic luminescent cyclometalated Ir(III) complexes with polypyridine co-ligands

Two novel ligands containing a functionalized N ∧ N chelating moiety (pbpy-OBut and tpy-COOH, respectively) were treated with [Ir(ppy)₂(μ-Cl)]₂ (ppy = 2-(2-pyridyl)phenyl), leading to the cationic cyclometalated complexes [Ir(ppy)₂(pbpy-OBut)]⁺ (2) (pbpy-OBut = 4-{4′-(4-phenyloxy)-6′-phenyl-2,2′-bipyridyl}butene) and [Ir(ppy)₂(tpy-COOH)]⁺ (3) (tpy-COOH = 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine). Complexes 2 and 3 exhibit intense room temperature luminescence both in solution and as solid films. Assignment of the emissive behavior to a ³LLCT (ppy-to-N ∧ N) excited state is proposed.     

Two new diphenyl ethers from Acanthopanax senticosus (Rupr. & Maxim.) Harms with PTP1B inhibitory activity

Bioassay-guided fractionation of an EtOAc-soluble extract of Acanthopanax senticosus (Rupr. & Maxim.) Harms yielded two new diphenyl ethers, 3-[3′-methoxy-4′-(4″-formyl-2″,6″-dimethoxy-phenoxy)-phenyl]-propenal (1) and 3-[3′,5′-dihydroxy-4′-(4″-hydroxymethyl-3″,5″-dimethoxy-phenoxy)-phenyl]-propenal (2), along with eight other known compounds (3–10). The structures of these new ethers were elucidated with spectroscopic and physico-chemical analyses. All of the isolates were evaluated for their in vitro inhibitory activity against PTP1B, VHR and PP1. The new compounds (1 and 2) inhibited PTP1B with IC₅₀ values ranging from 9.2 ± 1.4 to 12.6 ± 1.2 μM.     

‘3 + 1’ mixed-ligand oxorhenium(V) complexes and their inhibition of the cysteine proteases cathepsin B and cathepsin K

The synthesis of several new oxorhenium(V) complexes containing the ‘3 + 1’ mixed-ligand donor set, ReO(SXS)(SR) (where X = S, O, N(R′); R = alkyl, aryl, heterocylce; R′ = H, alkyl, aryl), is described. The X-ray structure for four of these complexes ReO(SN(Ph)S)(SPh) (6), ReO(SN(CH₂CH₂NMe₂)S)(SPhOMe-p) (10), ReO(SOS)(SPh) (29) and ReO(SOS)(SPhNO₂-p) (30) was determined. The inhibitory activity of all of the oxorhenium(V) complexes reported herein was evaluated against the cysteine proteases cathepsin B and K in vitro. Compound 25, ReO(SSS)(S-4py) · HCl, was the best inhibitor of the series against cathepsin B with an IC₅₀ of 10 nM. Several of the complexes exhibited specificity for cathepsin B over K, suggesting that oxorhenium(V) complexes can be designed to be enzyme specific. The results described in this paper show that the oxorhenium(V) ‘3 + 1’ complexes are potent inhibitors of cathepsin B and K, constituting promising potential for the treatment of cancer and osteoporosis, respectively.     

Two new N-heterocyclic carbene silver(I) complexes with the π–π stacking interactions

The precursors bis[N-(alkyl)benzimidazoliumylmethyl]durene halide (1a: alkyl = C₂H₅, halide = Br^?; 1b: alkyl = n-C₄H₉, halide = Cl^?; durene = 1,2,4,5-tetramethylbenzene) and their two new NHC silver(I) complexes [Durene(CH₂BimyEtAgBr)₂] (2a) and [Durene(CH₂BimyⁿBuAgCl)₂] (2b) (Bimy = benzimidazol-2-ylidene) have been prepared and characterized. In the crystal structures of 2a and 2b the aromatic π–π stacking interactions are observed.