Synthesis, spectral studies and in vitro assessment for antiamoebic activity of new cyclooctadiene ruthenium(II) complexes with 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones

We report here the synthesis, characterization and in vitro antiamoebic activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones (TSC), 1–5, and their bidentate complexes [Ru(η⁴-C₈H₁₂)(TSC)Cl₂] 1a–5a. The biological studies of these compounds were investigated against HK-9 strain of Entamoeba histolytica and the concentration causing 50% cell growth inhibition (IC₅₀) was calculated in the micromolar range. The ligands exhibited antiamoebic activity in the range (2.05–5.29 μM). Screening results indicated that the potencies of the compounds increased by the incorporation of ruthenium(II) in the thiosemicarbazones. The complexes 1a–5a showed antiamoebic activity with an IC₅₀ of 0.61–1.43 μM and were better inhibitors of growth of E. histolytica, based on IC₅₀ values. The most promising among them is Ru(II) complex 2a having 1,2,3,4-tetrahydroquinoline as N⁴ substitution.     

Inhibition of antennal esterases of the egyptian armyworm Spodoptera littoralis by trifluoromethyl ketones

A series of aliphatic and aromatic trifluoromethyl ketones has been tested as inhibitors of the antennal esterases of the Egyptian armyworm Spodoptera littoralis, by evaluation of the extent of hydrolysis of [1-³H]-(Z,E)-9, 11-tetradecadienyl acetate (1), a tritiated analog of the major component of the sex pheromone. The most active compounds with a long chain aliphatic structure were 3-octylthio-1,1,1-trifluoropropan-2-one (2) (IC₅₀ 0.55 μM) and 1,1,1-trifluorotetradecan-2-one (4) (IC₅₀ 1.16 μM). The aromatic compounds were generally less potent inhbitors than the coressponding aromatic ones, although β-naphthyltrifuloromethyl ketone (10) exhibited a remarkable inhibitory activity (IC₅₀ 7.9 μM). Compounds 2, 4 and 10 exhibit a competitive inhibition with K_i values of 2.51×10⁻⁵ M, 2.98×10⁻⁵ M and 2.49×10⁻⁴ M, respectively. Some of the trifluoromethyl ketones tested were slow-binding inhibitors and compounds 2 and 10 are described as inhibitors of the antennal esterases of a moth for the first time.     

Synthesis of derivatives of (1S,2R)-1-phenyl-2-[(S)-1-aminopropyl]-N,N-diethylcyclopropanecarboxamide (PPDC) modified at the 1-aromatic moiety as novel NMDA receptor antagonists: the aromatic group is essential for the activity

(1S,2R)-1-Phenyl-2-[(S)-1-aminopropyl]-N,N-diethylcyclopropanecarboxamide (PPDC, 4a), which is a conformationally restricted analogue of antidepressant milnacipran [(±)-1], is a new class of potent noncompetitive NMDA receptor antagonists. A series of PPDC analogues modified at the 1-phenyl moiety, that is, the analogue 6 lacking 1-phenyl group, the 1-(fluorophenyl) analogues 4b,c,d, the 1-(methylphenyl) analogues 4e–g and the 1-(naphthyl) analogues 4h,i were synthesized. Analogue 6, lacking the 1-phenyl group, was completely inactive showing that the aromatic moiety is essential for the NMDA receptor binding. Among the analogues synthesized, the 1-o-fluorophenyl and 1-m-fluorophenyl analogues 4b and 4c showed potent affinities for the NMDA receptor [IC₅₀=0.16±0.001 μM (4b), 0.15±0.02 μM (4c)], which were improved to some extent compared to those of the parent compound PPDC (IC₅₀=0.20±0.02 μM). On the other hand, compounds 4b and 4c showed none of the 5-HT-uptake inhibitory effect, while PPDC turned out to be a weak 5-HT-uptake inhibitor.     

Structure—activity studies leading to potent chloride channel blockers: 5e-tert-butyl-2-[4-(substituted-ethynyl)phenyl]-1,3-dithianes

5e-tert-Butyl-2e-[4-(substituted-ethynyl)phenyl]-1,3-dithianes with selected functional groups (R) on the ethynyl moiety are potent blockers of the GABA-gated chloride channel measured as inhibitor concentration (IC₅₀) for 4-n-[³H]propyl-1-(4-ethynylphenyl)-2, 6,7-trioxabicyclo[2.2.2]octanebinding to bovine brain membranes. The terminal R substituents were introduced by coupling 5e-tert-butyl-2e-(4-iodophenyl)-1,3-dithiane with HC ≡ CR or 5e-tert-butyl-2e-(4-ethynylphenyl)-1,3-dithiane with XR. The potency of the parent compound (R=H) with an IC₅₀ of 21 μM is equaled or exceeded by up to 7-fold (i.e. IC₅₀ = 3–21 μM) by several carboxylic acids [R = (CH₂)_nCO₂H (n = 0–3), (CH_2nOCH₂CO₂H (n = 1–3) and CH₂SCH₂ CO₂H] and their esters and two phosphonic acids (CH₂CH₂PO₃H₂ and CH₂OCH₂PO₃H₂) but not their esters. These carboxyl and phosphonic acids (and their salts) include the most potent water-soluble chloride channel blockers known. Conversion to the monosulfones increases activity of the R = H and CH₂OH analogs by 1.2- to 3-fold but decreases that of the R = CH₂CH₂CO₂R′ (R′ = H or CH₃) derivatives by 3- to 13-fold. Quantitative structure-activity analyses for 44 2-[4-(substituted-ethynyl)phenyl]-dithianes suggests that the principal feature of the R substituent for high activity is its polarizable volume modeled as molecular refractivity, i.e. this substituent is not a well-defined pharmacophore and undergoes a structurally non-specific interaction with the receptor. These observations lay the background for preparing candidate affinity probes.     

Synthesis and cell growth inhibitory properties of substituted (E)-1-phenylbut-1-en-3-ones

A series of (E)-1-phenylbut-1-en-3-ones, based on the naturally occurring (E)-1-(4′-hydroxyphenyl)but-1-en-3-one [IC₅₀ (K562) 60 μM], was synthesised and screened for cytotoxic activity against the K562 human leukaemia cell line. (E)-1-(Pentafluorophenyl)but-1-en-3-one [IC₅₀ (K562) 1.8 μM] was found to be over 30-fold more active than 1.     

Anti-proliferative lichen compounds with inhibitory activity on 12(S)-HETE production in human platelets

Several lichen compounds, i.e. lobaric acid (1), a β-orcinol depsidone from Stereocaulon alpinum L., (+)-protolichesterinic acid (2), an aliphatic -methylene-γ-lactone from Cetraria islandica Laur. (Parmeliaceae), (+)-usnic acid (3), a dibenzofuran from Cladonia arbuscula (Wallr.) Rabenh. (Cladoniaceae), parietin (4), an anthraquinone from Xanthoria elegans (Link) Th. Fr. (Calaplacaceae) and baeomycesic acid (5), a β-orcinol depside isolated from Thamnolia vermicularis (Sw.) Schaer. var. subuliformis (Ehrh.) Schaer. were tested for inhibitory activity on platelet-type 12(S)-lipoxygenase using a cell-based in vitro system in human platelets. Lobaric acid (1) and (+)-protolichesterinic acid (2) proved to be pronounced inhibitors of platelet-type 12(S)-lipoxygenase, whereas baeomycesic acid (5) showed only weak activity (inhibitory activity at a concentration of 100 μg/ml: 1 93.4±6.62%, 2 98,5±1.19%, 5 14.7±2.76%). Usnic acid (3) and parietin (4) were not active at this concentration. 1 and 2 showed a clear dose–response relationship in the range of 3.33–100 μg/ml. According to the calculated IC₅₀ values the highest inhibitory activity was observed for the depsidone 1 (IC₅₀=28.5 μM) followed by 2 (IC₅₀=77.0 μM). The activity of 1 was comparable to that of the flavone baicalein, which is known as a selective 12(S)-lipoxygenase inhibitor (IC₅₀=24.6 μM).     

Probing the opioid receptor complex with (+)-trans-SUPERFIT. II. Evidence that mu ligands are noncompetitive inhibitors of the delta cx opioid peptide binding site.

Previous studies delineated two classes of δ binding sites; a δ binding site not associated with the opioid receptor complex, termed the δ_ncx site, and a δ site associated with the opioid receptor complex, termed the δ_cx site. The δ_ncx site has high affinity for [ -Pen², -Pen⁵]enkephalin, and is synonymous with what is now identified as the δ₁ binding site. Pretreatment of membranes with the δ-selective acylating agents FIT, or (+)-trans-SUPERFIT, deplete membranes of the δ_ncx binding site, which permits the selective labeling of the δ_cx binding site with [³H][ -Ala²,Leu⁵]enkephalin. The present study compared the properties of the δ_cx binding site present in brain membranes pretreated with (+)-trans-SUPERFIT with the properties of the δ_cx site present in untreated membranes. The major findings are: 1) pretreatment of membranes with (+)-trans-SUPERFIT decreased the IC₅₀ values of δ-preferring drugs, and increased the IC₅₀ values of μ-preferring drugs, for the δ_cx binding site; 2) the degree of δ selectivity was highly correlated with the magnitude of the (+)-trans-SUPERFIT-induced shift in the IC₅₀ values; 3) the ligand-selectivity patterns of the μ and δ_cx sites present in (+)-trans-SUPERFIT-pretreated membranes were poorly correlated; 4) whereas μ-preferring drugs were noncompetitive inhibitors of [³H][ -Ala²,Leu⁵]enkephalin binding to the δ_cx site, δ-preferring drugs were competitive inhibitors. Viewed collectively, these data support the hypothesis that the μ and δ_cx binding sites are distinct, provide additional evidence for δ receptor heterogeneity, and suggest that ( (+)-trans-SUPERFIT-pretreated membranes will provide a useful preparation for studying the δ_cx binding site.     

Natural products isolated from Mexican medicinal plants: Novel inhibitors of sulfotransferases, SULT1A1 and SULT2A1

Calophyllum brasiliense, Lonchocarpus oaxacensis, and Lonchocarpus guatemalensis are used in Latin American folk medicine. Four natural xanthones, an acetylated derivative, and two coumarins were obtained from C. brasiliense. Two flavanones were extracted from L. oaxacensis and one chalcone from L. guatemalensis. These compounds were tested as substrates and inhibitors for two recombinant sulfotransferases (SULTs) involved in the metabolism of many endogenous compounds and foreign chemicals. Assays were performed using recombinant phenol-sulfotransferase (SULT1A1) and hydroxysteroidsulfotransferase (SULT2A1). Three of the five xanthones, one of the flavonoids and the coumarins tested were substrates for SULT1A1. None of the xanthones or the flavonoids were sulfonated by SULT2A1, whereas the coumarin mammea A/BA was a substrate for this enzyme. The natural xanthones reversibly inhibited SULT1A1 with IC₅₀ values ranging from 1.6 to 7 μM whereas much higher amounts of these compounds were required to inhibit SULT2A1 (IC₅₀ values of 26-204 μM). The flavonoids inhibited SULT1A1 with IC₅₀ values ranging from 9.5 to 101 μM, which compared with amounts needed to inhibit SULT2A1 (IC₅₀ values of 11 to 101 μM). Both coumarins inhibited SULT1A1 with IC₅₀ values of 47 and 185 μM, and SULT2A1 with IC₅₀ values of 16 and 31 μM. The acetylated xanthone did not inhibit either SULT1A1 or SULT2A1 activity. Rotenone from a commercial source had potency comparable to that of the flavonoids isolated from Lonchocarpus for inhibiting both SULTs. The potency of this inhibition depends on the position and number of hydroxyls. The results indicate that SULT1A1, but not SULT2A1, is highly sensitive to inhibition by xanthones. Conversely, SULT2A1 is 3-6 times more sensitive to coumarins than SULT1A1. The flavonoids are non-specific inhibitors of the two SULTs.

Collectively, the results suggest that these types of natural products have the potential for important pharmacological and toxicological interactions at the level of phase-II metabolism via sulfotransferases.     

Modification at the C9 position of the marine natural product isoaaptamine and the impact on HIV-1, mycobacterial, and tumor cell activity

As part of an investigation to generate optimized drug leads from marine natural pharmacophores for the treatment of neoplastic and infectious diseases, a series of novel isoaaptamine analogs were prepared by coupling acyl halides to the C9 position of isoaaptamine (2) isolated from the Aaptos sponge. This library of new semisynthetic products was evaluated for biological activity against HIV-1, Mtb, AIDS-OI, tropical parasitic diseases, and cancer. Compound 4 showed potent activity against HIV-1 (EC₅₀ 0.47 μg/mL), compound 19 proved to possess remarkable activity against Mycobacterium intracellulare with an IC₅₀ and MIC value of 0.15 and 0.31 μg/mL, while compounds 4 and 17 possessed anti-leishmanial activity with IC₅₀ values of 0.1 and 0.4 μg/mL, respectively. Compounds 16 and 17 showed antimalarial activity with EC₅₀ values of 230 and 240 ng/mL, respectively, and compound 14 exhibited an EC₅₀ of 0.05 μM against the Leukemia cell line K-562.     

In vitro antiplasmodial activity of extract and constituents from Esenbeckia febrifuga, a plant traditionally used to treat malaria in the Brazilian Amazon

Esenbeckia febrifuga (Rutaceae) is a plant traditionally used to treat malaria in the Brazilian Amazon region. Ethanol extract of stems displayed a good antiplasmodial activity against Plasmodium falciparum strains W-2 (IC₅₀ 15.5±0.71 μg/ml) and 3 D7 (IC₅₀ 21.0±1.4 μg/ml). Two coumarins (bergaptene 1 and isopimpinellin 2), five alkaloids (flindersiamine 3, kokusaginine 4, skimmiamine 5, γ-fagarine 6 and 1-hydroxy-3-methoxy-N-methylacridone, 7), besides a limonoid (rutaevine 8), have been isolated for the first time from this species. Antiplasmodial activity of compounds 3, 5–8 has been evaluated in vitro against P. falciparum strains (W-2 and 3D7) and the furoquinolines 5 and 6 were the most potent displaying IC₅₀ values <50 μg/ml; flindersiamine (3) showed a weak activity while alkaloid 7 and rutaevine (8) were inactive (IC₅₀>100 μg/ml).     

Crystallographic and NMR studies of antiinfective tricyclic guanidine alkaloids from the sponge Monanchora unguifera

Three tricyclic guanidine alkaloids, including 1,8a;8b,3a-didehydro-8β-hydroxyptilocaulin (1), 1,8a;8b,3a-didehydro-8-hydroxyptilocaulin (2) and mirabilin B (3), were identified from the marine sponge Monanchora unguifera. 1,8a;8b,3a-Didehydro-8-hydroxyptilocaulin (2) is a new stereoisomer of 1, the structure of which was elucidated by spectroscopic analysis, comparison of its spectral data with those of 1, and confirmed by X-ray analysis. Compounds 1 and 2 co-crystallized in an unusual perfect order and packed around an approximate inversion center. A mixture of 1 and 2 is active against the malaria parasite Plasmodium falciparum with an IC₅₀ value of 3.8 μg/mL while mirabilin B (3) exhibited antifungal activity against Cryptococcus neoformans with an IC₅₀ value of 7.0 μg/mL and antiprotozoal activity against Leishmania donovani with an IC₅₀ value of 17 μg/mL.     

Inhibition of the HIV-1 and HIV-2 proteases by curcumin and curcumin boron complexes

Curcumin, a relatively non-toxic natural product isolated from Curcuma longa, is a modest inhibitor of the HIV-1 (1050 = 100 μM) and HIV-2 (IC₅₀ = 250 μM) proteases. Simple modifications of the curcumin structure raise the IC₅₀ value but complexes of the central dihydroxy groups of curcumin with boron lower the IC₅₀ to a value as low as 6 μM. The boron complexes are also time-dependent inactivators of the HIV proteases. The increased affinity of the boron complexes may reflect binding of the orthogonal domains of the inhibitor in intersecting sites within the substrate-binding cavity of the enzyme, while activation of the ,β-unsaturated carbonyl group of curcumin by chelation to boron probably accounts for time-dependent inhibition of the enzyme.     

1,5-Disubstituted 1,2,3-triazoles as cis-restricted analogues of combretastatin A-4: Synthesis, molecular modeling and evaluation as cytotoxic agents and inhibitors of tubulin

A series of cis-restricted 1,5-disubstituted 1,2,3-triazole analogues of combretastatin A-4 (1) have been prepared. The triazole 12f, 2-methoxy-5-(1-(3,4,5-trimethoxyphenyl)-1H-1,2,3-triazol-5-yl)aniline, displayed potent cytotoxic activity against several cancer cell lines with IC₅₀ values in the nanomolar range. The ability of triazoles to inhibit tubulin polymerization has been evaluated, and 12f inhibited tubulin polymerization with IC₅₀ = 4.8 μM. Molecular modeling experiments involving 12f and the colchicine binding site of ,β-tubulin showed that the triazole moiety interacts with β-tubulin via hydrogen bonding with several amino acids.     

-cyano-substituted analogoues of decarboxylated S-adenosylmethionine as enzyme activated, irreversible inhibitors of S-adenosylmethionine decarboxylase

A pair of -cyano analogues of decarboxylated S-adenosylmethionine (2a and 2b) were synthesized as potential enzyme activated, irreversible inhibitors of the[pyruvoyl enzyme S-adenosylmethionine decarboxylase (AdoMet-DC). Each of these analogues acts as an irreversible inactivator for ADoMet-DC from Escherichia coli (IC₅₀ values of 9 and 50 μM, respectively). These analogues also inactivate human AdoMet-DC, with K_I values of 246.6 and 7.2 μM, and k_inact values of 0.29 and 0.03 min⁻¹, respectively.     

Polynuclear copper(II) complexes with μ2-1,1-azide bridges. Structural and magnetic properties

Two novel, weakly antiferromagnetically coupled, tetranuclear copper(II) complexes [Cu₄(PAP)₂(μ₂-1,1-N₃)₂(μ₂-1,3-N₃)₂(μ₂-CH₃OH)₂(N₃)₄ (1) (PAP = 1,4-bis-(2′-pyridylamino)phthalazine) and [Cu₄(PAP3Me)₂ (μ₂-1,1-N₃)₂(μ₂-1,3-N₃)₂(H₂O)₂(NO₂)₂]- (NO₃)₂ (2) (PAP3Me = 1,4-bis-(3′-methyl-2′-pyridyl)aminophthalazine) contain a unique structural with two μ₂-1,1-azide intramolecular bridges, and two μ₂-1,3-azide intermolecular bridges linking pairs of copper(II) centers. Four terminal azide groups complete the five-coordinate structures in 1, while two terminal waters and two nitrates complete the coordination spheres in 2. The dinuclear complexes [Cu₂(PPD)(μ₂-1,1-N₃)(N₃)₂(CF₃SO₃)]CH₃OH) (3) and [Cu₂(PPD)(μ₂-1,1-N₃)(N₃)₂(H₂O)(ClO₄)] (4) (PPD = 3,6-bis-(1′-pyrazolyl)pyridazine) contain pairs of copper centers with intramolecular μ₂-1,1-azid and pyridazine bridges, and exhibit strong antiferromagnetic coupling. A one-dimensional chain structure in 3 occurs through intermolecular μ₂-1,1-azide bridging interactions. Intramolecular Cu-N₃-Cu bridge angles in 1 and 2 are small (107.9 and 109.4°, respectively), but very large in 3 and 4 (122.5 and 123.2°, respectively), in keeping with the magnetic properties. 2 crystallizes in the monoclinic system, space group C2/c with a = 26.71(1), b = 13.51(3), c = 16.84(1) Å, β = 117.35(3)° and R = 0.070, R_w = 0.050. 3 crystallizes in the monoclinic system, space group P2₁/c with a = 8.42(1), b = 20.808(9), c = 12.615(4) Å, β = 102.95(5)° and R = 0.045, R_w = 0.039. 4crystallizes in the triclinic system, space group P1, with a = 10.253(3), b = 12.338(5), c = 8.072(4) Å, = 100.65(4), β = 101.93(3), γ = 87.82(3)° and R = 0.038, R_w = 0.036 . The magnetic properties of 1 and 2 indicate the presence of weak net antiferromagnetic exchange, as indicated by the presence of a low temperature maximum in χ_m (80 K (1), 65 K (2)), but the data do not fit the Bleaney-Bowers equation unless the exchange integral is treated as a temperature dependent term. A similar situation has been observed for other related compounds, and various approaches to the problem will be discussed. Magnetically 3 and 4 are well described by the Bleaney-Bowers equation, exhibiting very strong antiferromagnetic exchange (− 2J = 768(24) cm⁻¹ (3); − 2J = 829(11) cm⁻¹ (4)).     

Ionic iridium-gold and rhodium-gold perfluorobenzenethiolato binuclear complexes: syntheses and solution behavior

By reacting [(C₅Me₅)M(SR_F)₂] (forM = Ir, Rf = C₆F₅ (1a) or C₆F₄H-p (1b); for M = Rh, Rf = C₆F₅ (2a) or C₆F₄H-p (2a)) in toluene with Na[AuCl₄], ionic binuclear compounds with the general formula [(C₅Me₅)M(μ-SR_F)₂AuCl₂]Cl for M = Ir, R = C₆F₅ (3a) or C₆F₄H-p (3a); for M = Rh, R_F = C₆F₅ (4a) or C₆F₄H-p (4b) can be obtained, together with small amounts of [(C₅Me₅)₂Rh₂(μ-SR_F)(μ-Cl)₂]Cl (R_F = C₆F₅ (5a) or C₆F₄H-p (5b)) as by-products when 2a and 2b were used.     

Anti-allergic substances from the rhizomes of Dioscorea membranacea

Extracts of five species of Thai medicinal plants, locally known as Hua-Khao-Yen, were screened for anti-allergic activities using RBL-2H3 cells. Of the five species studied, the ethanolic extract of Dioscorea membranacea exhibited potent inhibitory activity against β-hexosaminidase release as a marker of degranulation in RBL-2H3 cells, with an IC₅₀ value of 37.5 μg/mL. Eight compounds were isolated from this crude ethanolic extract, [two naphthofuranoxepins (1, 2), one phenanthraquinone (3), three steroids (4–6), and two steroidal saponins (7, 8)], and tested for their anti-allergic activities. The results showed that dioscorealide B (2) possessed the highest activity with an IC₅₀ value of 5.7 μM, followed by dioscoreanone (3, IC₅₀ = 7.7 μM), dioscorealide A (1, IC₅₀ = 27.9 μM), and diosgenin (9, IC₅₀ = 29.9 μM). Structure–activity relationship studies of naphthofuranoxepins on anti-allergic activity revealed that the hydroxylation at position 8 conferred higher activity than methoxylation. For diosgenin derivatives, the aglycone was found to possess higher activity than the diglucosylated molecule; whereas substitution with rhamnoglucosides apparently results in loss of activity. Furthermore, effects of dioscorealide A, dioscorealide B, and dioscoreanone on antigen-induced release of TNF- and IL-4 in the late phase reaction were also examined.     

Beta(3)-adrenoceptor agonists for the treatment of frequent urination and urinary incontinence: 2-[4-(2-[[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino]ethyl)phenoxy]-2-methylpropionic acid.

In a search for novel analogues of β₃-adrenoceptor (AR) agonists relaxing the bladder for treatment of urinary dysfunction, 2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)phenoxy]-2-methylpropionic acids (1a–e), into which a fibrate-like structure had been incorporated, were synthesised. Compound 1a was found to be a selective β₃-AR agonist in functional assays using the ferret detrusor (β₃-AR), rat uterus (β₂-AR), and rat atrium (β₁-AR); β₃: EC₅₀=7.8 nM, β₂: IC₅₀=7,300 nM, β₁: EC₂₀=23,000 nM. The introduction of a chlorine atom or methyl substituent at the ortho-position on the phenyl ring of 1a further improved β₃-AR selectivity. In an in vivo study, 1a lowered intrabladder pressure (ED₅₀=31 μg/kg) in rats, without increasing heart rate, in keeping with the in vitro results. Consequently, it is proposed that 1a and its analogues (1b–e), possess β₃-AR agonistic activity in the absence of undesirable β₁- or β₂-AR mediated actions, and may be useful for clinical treatment and pharmacological studies.     

The synthesis of three 4-substitutedbenzo[b]thiophene-2-carboxamidines as potent and selective inhibitors of urokinase

Efficient syntheses of structurally novel 4-substituted benzo[b]thiophene-2-carboxamidmes 1–3, which selectively inhibit urokinase-type plasminogen activator (uPA) with IC₅₀ values of 70–320 nM, are described. The key intermediate, methyl 4-iodobenzo[b]thiophene-2-carboxylate (7), is prepared from 3-fluoroiodobenzene in two steps in 70% overall yield via fluorine-directed metalation/formylation and subsequent thiophene annulation. Amidination of ester 7 gives the 320 nM inhibitor 1. Palladium-catalyzed arylacetylene and vinyl stannane couplings with ester 7 or 4-iodobenzo[b]thiophene-2-carbonitrile (16, derived from 7), respectively, followed by amidination leads to the more potent inhibitors 2 (IC₅₀ = 133 nM) and 3 (IC₅₀ = 70 nM). These compounds represent an important new class of synthetic uPA inhibitors, with carboxamidine 3 being the most potent selective inhibitor currently described in the literature.