Synthesis of Coumarin Derivatives as Inhibitors of Platelet Aggregation

In a search for the inhibitors of platelet aggregation, certain coumarin derivatives were synthesized and evaluated for antiplatelet activity against thrombin(Thr)-, arachidonic acid(AA)-, collagen(Col)-, and platelet-activating-factor(PAF)-induced aggregation in washed rabbit platelets. These compounds were synthesized from 4-hydroxycoumarin ( 1 ) or naphthalen-1-ol via alkylation and Reformatsky-type condensation (Schemes 1–3). Among them, 4-[(2,3,4,5-tetrahydro-4-methylidene-5-oxo-2-phenylfuran-2-yl)methoxy]-2H-1-benzopyran-2-one ( 6b ) showed potent antiplatelet effects on AA- and PAF-induced aggregation with IC₅₀ values of 8.21 and 103.67 m?M , respectively (see Tables 1 and 2). The antiplatelet potency of 6b against PAF-induced aggregation could be further improved by introducing a proper substituent at the 2-phenyl group of the lactone ring.     

Synthesis and urease inhibition studies of some new quinazolinones

In this study, novel quinazolinones were designed, synthesized, characterized by FT-IR, ¹H-NMR, ¹³C-NMR spectral data, and LC–MS. New compounds inhibitory activities on urease were assessed. All of the compounds exhibited potent urease inhibitory activities. Especially in the synthesized compounds, 2-benzyl-3-({5-[(4-nitrophenyl)amino]-1,3,4-thiadiazol2-yl}methyl)quinazolin-4(3H)-one has the best inhibitory effect against Jack bean urease with IC₅₀ = 3.30 ± 0.09 μg/mL. And also, N-(4-nitrophenyl)-2-[(4-oxoquinazolin-3(4H)-yl)acetyl] hydrazinecarbothioamide, N-(4-fluorophenyl)-2-[(4-oxoquinazolin-3(4H)-yl)acetyl] hydrazinecarbothioamide, and 2-benzyl-3-({5-[(4-fluorophenyl)amino]-1,3,4-thiadiazol-2yl} methyl)quinazolin-4(3H)-one have best activities among the synthesized compounds.     

Synthesis of new functionally substituted hetarylcarbamates from methyl {4-[(2<Emphasis Type="Italic">E</Emphasis>)-3-(4-methoxyphenyl)-prop-2-enoyl]phenyl}carbamate

Three-component condensation of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}- carbamate with ninhydrin and L-proline in methanol–water (10: 1) afforded methyl {4-[1,3-dioxo-1′- (4-methoxyphenyl)-1,1′,2′,3,5′,6′,7′,7a′-octahydrospiro[indene-2,3′-pyrrolizin]-2′-ylcarbonyl]phenyl}carbamate. Heating of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}carbamate with isatin and benzylamine in methanol gave methyl {4-[4′-(4-methoxyphenyl)-2-oxo-5′-phenyl-1,2-dihydrospiro[indole-3,2′-pyrrolidin]-3′-ylcarbonyl]phenyl}carbamate. The condensation of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2- enoyl]phenyl}carbamate with sarcosine and 11H-indeno[1,2-b]quinoxalin-11-one generated in situ from ninhydrin and o-phenylenediamine in boiling ethanol led to the formation of methyl {4-[4′-(4-methoxyphenyl)-1′-methyl-11,11a-dihydro-5aH-spiro[benzo[b]phenazine-6,2′-pyrrolidin]-3′-ylcarbonyl]phenyl}carbamate.     

Synthesis and biological evaluation of peptidyl organotrifluoroborates and their corresponding boron analogs

Six peptidyl organotrifluoroborates and their corresponding boronate esters and/or boronic acid analogs were designed and synthesized. Their anti-proliferative activity against hepatocellular carcinoma cells (HepG2) and human metastatic breast cancer cells (MDA-MB231) were evaluated by use of an MTT assay. Potassium {4-[(3S,6S,9S)-3,6-dibenzyl-9-isopropyl-4,7,10-trioxo-11-oxa-2,5,8-triazadodecyl]phenyl}trifluoroborate (B6) was potent (IC₅₀ = 29.9 μM) against MDA-MB231, and {4-[(3S,6S,9S)-6-benzyl-3-((benzyloxy)methyl)-9-isopropyl-4,7,10-trioxo-11-oxa-2,5,8-triazadodecyl]phenyl}boronic acid (B9) and Potassium {4-[(3S,6S,9S)-6-benzyl-3-((benzyloxy)methyl)-9-isopropyl-4,7,10-trioxo-11-oxa-2,5,8-triazadodecyl]phenyl}trifluoroborate (B10) had broad anti-proliferative activity against HepG2 (IC₅₀ = 24.7 and 21.8 μM, respectively) and MDA-MB231 (IC₅₀ = 24.5 and 18.9 μM, respectively).     

Synthesis and Antiplatelet‐Activity Evaluation of α‐Methylidene‐γ‐butyrolactones Bearing 3,4‐Dihydroquinolin‐2(1H)‐one Moieties

In continuation of our search for potent antiplatelet agents, we have synthesized and evaluated several α‐methylidene‐γ‐butyrolactones bearing 3,4‐dihydroquinolin‐2(1H)‐one moieties. O‐Alkylation of 3,4‐dihydro‐8‐hydroxyquinolin‐2(1H)‐one ( 1 ) with chloroacetone under basic conditions afforded 3,4‐dihydro‐8‐(2‐oxopropoxy)quinolin‐2(1H)‐one ( 2a ) and tricyclic 2,3,6,7‐tetrahydro‐3‐hydroxy‐3‐methyl‐5H‐pyrido[1,2,3‐de][1,4]benzoxazin‐5‐one ( 3a ) in a ratio of 1 : 2.84. Their Reformatsky‐type condensation with ethyl 2‐(bromomethyl)prop‐2‐enoate furnished 3,4‐dihydro‐8‐[(2,3,4,5‐tetrahydro‐2‐methyl‐4‐methylidene‐5‐oxofuran‐2‐yl)methoxy]quinolin‐2(1H)‐one ( 4a ), which shows antiplatelet activity, in 70% yield. Its 2′‐Ph derivatives, and 6‐ and 7‐substituted analogs were also obtained from the corresponding 3,4‐dihydroquinolin‐2(1H)‐ones via alkylation and the Reformatsky‐type condensation. Of these compounds, 3,4‐dihydro‐7‐[(2,3,4,5‐tetrahydro‐4‐methylidene‐5‐oxo‐2‐phenylfuran‐2‐yl)methoxy]quinolin‐2(1H)‐one ( 10b ) was the most active against arachidonic acid (AA) induced platelet aggregation with an IC₅₀ of 0.23 μM . For the inhibition of platelet‐activating factor (PAF) induced aggregation, 6‐{[2‐(4‐fluorophenyl)‐2,3,4,5‐tetrahydro‐4‐methylidene‐5‐oxofuran‐2‐yl]methoxy}‐3,4‐dihydroquinolin‐2(1H)‐one ( 9c ) was the most potent with an IC₅₀ value of 1.83 μM .     

<Emphasis Type="Italic">cis</Emphasis>-Tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes: Synthesis and mesomorphic properties

Hydrolytic condensation of organotrialkoxysilanes RSi(OR′)₃ (R = Me, Et, Pr, CH=CH₂; R′ = OMe, OEt) in the presence of sodium and/or potassium hydroxide gave new alkali organosiloxanolates {(M⁺)₄[RSi(O)O⁻]₄}·nL (R = Me, Et, Pr, CH=CH₂; M = Na, K; L = R′OH, H₂O) in which the main structural fragment is the cyclotetrasiloxanolate fragment cis-[RSi(O)O⁻]₄. Based on these organosiloxanolates, a series of cis-tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes was synthesized. For new cyclotetrasiloxanes, the thermotropic transitions and mesomorphic orderings were determined by differential scanning calorimetry, X-ray diffraction analysis, and polarization microscopy. In addition, new mesomorphic compounds were revealed. The character of thermotropic and time evolution of the phase state was found for a mixture of cis-tetra[ethyl(trimethylsiloxy)]-and cis-tetra[phenyl(trimethylsiloxy)]cyclotetrasiloxanes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 80–86, January, 2007.     

Synthesis and structure of alkyl 2-arylsulfanyl-3-nitroacrylates

Alkyl 2-arylsulfanyl-3-nitroacrylates were synthesized by the conjugate Michael addition of thiophenols to alkyl 3-bromo-3-nitroacrylates followed by elimination of HBr on treatment with Et₃N. When treated with 4-chlorothiophenol in the presence of Et₃N, alkyl 2-[(4-chlorophenyl) sulfanyl]-3-nitroacrylates can be transformed into alkyl 2,3-bis[(4-chlorophenyl)sulfanyl]- acrylates. The structures of the synthesized compounds were characterized by IR, UV, ¹H and ¹³C{¹H} NMR spectroscopy using ¹H–¹³C HMQC, ¹H–¹³C, and ¹H–¹⁵N HMBC techniques. Methyl 2-[(4-methylphenyl)sulfanyl]-3-nitroacrylate exists as the Z-isomer, as confirmed by X-ray diffraction.     

Novel 5‐Methyl‐2‐[(un)substituted phenyl]‐4‐{4,5‐dihydro‐ 3‐[(un)substituted phenyl]‐5‐(1,2,3,4‐tetrahydroisoquinoline‐2‐yl)pyrazol‐1‐yl}‐oxazole Derivatives: Synthesis and Anticancer Activity

Eleven novel 5‐methyl‐2‐[(un)substituted phenyl]‐4‐{4,5‐dihydro‐3‐[(un)substituted phenyl]‐5‐(1,2,3,4‐tetrahydroisoquinoline‐2‐yl)pyrazol‐1‐yl}‐oxazole derivatives were synthesized and characterized by elemental analysis, ESI‐MS, ¹H NMR and ¹³C NMR. All of the compounds have been screened for their antiproliferative activities against PC‐3 cell (human prostate cancer) and A431 cell (human epidermoid carcinoma cancer) lines in vitro. The results revealed that compounds 4g , 4j and 4k exhibited the strong inhibitory activities against the PC‐3 cell lines (with IC₅₀ values of 2.8±0.11, 3.1±0.10 and 3.0±0.06 μg/mL, respectively).     

Synthesis and antimicrobial and pharmacological properties of new thiosemicarbazide and 1,2,4‐triazole derivatives

Reaction of 4‐phenyl‐4H‐1,2,4‐triazole‐3‐thione with ethyl bromoacetate has led to the formation of ethyl [(4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)sulfanyl]acetate 1 , the structure of which was confirmed by X‐ray analysis. In the next reaction with 80% hydrazide hydrate, appropriate hydrazide 2 was obtained, which in reaction with isothiocyanates was converted to new acyl derivatives of thiosemicarbazides 2 , 3 , 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h . The cyclization of these compounds in alkaline media has led to formation of new derivatives of 5‐{[(4‐phenyl‐4H‐1,2,4‐triazole‐3‐yl)sulfanyl]methyl}‐4H‐1,2,4‐triazole‐3(2H)‐thiones 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4j . The structure of the compounds was confirmed by elementary analysis and IR, ¹H‐NMR, ¹³C‐NMR, and MS spectra. Compounds 2 , 3 , 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h and 4a , 4b , 4c , 4d , 4e , 4f , 4g were screened for their antimicrobial activities, and the influence of the compounds 4a , 4b , and 4e , 4f , 4g on the central nervous system of mice in behavioral tests was examined. J. Heterocyclic Chem., (2011).     

Formation of an unexpected rearrangement product using Grubbs’ second generation catalyst: 2-allyl-3,4-dihydro-2H-1,4-benzothiazines from diene precursors

Application of sub-stoichiometric amounts of Grubbs’ second generation catalyst to the substrate N-allyl-N-[2-(allylsulfanyl)phenyl]-4-methylbenzenesulfonamide afforded the ring-closed compound 6-[(4-methylphenyl)sulfonyl]-5,6-dihydro-2H-1,6-benzothiazocine, as well as the unexpected 2-allyl-4-[(4-methylphenyl)sulfonyl]-3,4-dihydro-2H-1,4-benzothiazine. Use of similar conditions on an analogous sulfoxide resulted in the expected product, 6-[(4-methylphenyl)sulfonyl]-5,6-dihydro-2H-1,6-benzothiazocine 1-oxide, indicating that the sulfide was playing a key role in this novel transformation. Furthermore, the use of N-allyl-4-methyl-N-{2-[(2-methyl-2-propenyl)sulfanyl]phenyl}-benzenesulfonamide in the same reaction gave 2-(2-methyl-2-propenyl)-3,4-dihydro-2H-1,4-benzothiazine.     

Synthesis of optically active 4,4,4-trifluoro-3-{4-(4-methoxyphenyl)phenyl}butanoic acid and its application to chiral dopant for nematic liquid crystals

We synthesized an optically active 4,4,4-trifluoro-3-{4-(4-methoxyphenyl)phenyl}butanoic acid (5^*). New chiral dopants for nematic liquid crystals were derived from (R)-(−)-5^*, and their helical twisting power (HTP) values were measured. Their HTP values were largely influenced by the linkage between the asymmetric frame and the core moiety. The chiral dopant, (R)-(+)-4,4,4-trifluoro-1-(4-hexyloxyphenyl)-3-{4-(4-methoxyphenyl)phenyl}-1-butanone ((R)-(+)-7^*) showed the largest HTP value (−21.7 μm⁻¹).     

Synthesis of Novel Disubstituted Pyrazolo[1,5‐a]pyrimidines,Imidazo[1,2‐a]pyrimidines,and Pyrimido[1,2‐a]benzimidazoles Containing Thioether and Aryl Moieties

A series of novel 6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐7‐phenylpyrazolo[1,5‐a]pyrimidines, 5‐phenyl‐6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]imidazo[1,2‐a]pyrimidines, and 2‐phenyl‐3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]pyrimido[1,2‐a]benzimidazoles have been synthesized in four steps starting with 2‐hydroxyacetophenone. The intermediate 3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐4H‐1‐benzopyran‐4‐ones reacted with pyrazol‐3‐amines, 5‐methylpyrazol‐3‐amine, and 1H‐imidazol‐2‐amine, 1H‐benzimidazol‐2‐amine via a cyclocondensation to give the title compounds in the presence of MeONa as base, respectively. The approach affords the target compounds in acceptable‐to‐good yields. The new compounds were characterized by their IR, NMR, and HR mass spectra.     

Synthesis of macrocyclic tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane in carbonic acid solution

The possibility to synthesize stereoregular tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane (tris-cis-tris-trans-[PhSi(O)OH]12) in an inorganic liquid medium – aqueous carbonic acid solution – was shown. The interaction of polyhedral phenylcoppersodiumsiloxane, {[(C₆H₅Si(O)O^?]₁₂(Cu₂⁺)₄(Na⁺)₄}*(L)_m (L?=?Buⁿ OH, H₂O), with carbonic acid can be considered as a new ‘green’ method to obtain functional organosiloxane macrocycles. In contrast to the known methods, no organic solvents were used during the reaction. The identification of the structure of the end compound was performed by means of NMR and Infrared spectroscopy as well as X-ray crystallography.     

Synthesis,antioxidant and antitumor activities of some of new cyclobutane containing triazoles derivatives

Abstract

Thiosemicarbazides (2a–e) were obtained by the interaction of furan-2-carboxylic acid hydrazide (1) with five different isothiocyanate (RNCS) derivatives. By addition of KOH to the reaction medium, ethyl, allyl, phenyl and benzyl, p-tolyl substituted 1,2,4-triazoles (3a–e) were obtained. 3a–e were dissolved in dry acetone containing K₂CO₃ in the presence of 2-chloro-1-(3-methyl-3-mesitylcyclobutyl) ethanone (4) to give 3,4,5-trisubstituted 1,2,4-triazole sulfanyl compounds containing a cyclobutane ring (5a–e). The structures of the final compounds were confirmed by elemental analyses, FT-IR, ¹H-NMR and ¹³C-NMR. The antioxidant and antitumor properties of the synthesized compounds were also investigated. Three of the triazole derivatives with p-tolyl, benzyl and phenyl substituents (5c–e) displayed good antioxidant and antitumor activity in comparison to the standards.     

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)platinum(II)]

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)platinum(II)], [Pt₂(C₁₅H₁₉O₄)₂Cl₂], containing a derivative of the natural compound eugenol as ligand, have been performed. Using five different sets of crystallization conditions resulted in four different complexes which can be further used as starting compounds for the synthesis of Pt complexes with promising anticancer activities. In the case of vapour diffusion with the binary chloroform–diethyl ether or methylene chloride–diethyl ether systems, no change of the molecular structure was observed. Using evaporation from acetonitrile (at room temperature), dimethylformamide (DMF, at 313 K) or dimethyl sulfoxide (DMSO, at 313 K), however, resulted in the displacement of a chloride ligand by the solvent, giving, respectively, the mononuclear complexes (acetonitrile‐κN)(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chloridoplatinum(II) monohydrate, [Pt(C₁₅H₁₉O₄)Cl(CH₃CN)]·H₂O, (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethylformamide‐κO)platinum(II), [Pt(C₁₅H₁₉O₄)Cl(C₂H₇NO)], and (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethyl sulfoxide‐κS)platinum(II), determined as the analogue {η²‐2‐allyl‐4‐methoxy‐5‐[(ethoxycarbonyl)methoxy]phenyl‐κC¹}chlorido(dimethyl sulfoxide‐κS)platinum(II), [Pt(C₁₄H₁₇O₄)Cl(C₂H₆OS)]. The crystal structures confirm that acetonitrile interacts with the Pt^II atom via its N atom, while for DMSO, the S atom is the coordinating atom. For the replacement, the longest of the two Pt—Cl bonds is cleaved, leading to a cis position of the solvent ligand with respect to the allyl group. The crystal packing of the complexes is characterized by dimer formation via C—H…O and C—H…π interactions, but no π–π interactions are observed despite the presence of the aromatic ring.     

Synthesis and platelet aggregation inhibitory activity of diphenylazole derivatives. I. Thiazole and imidazole derivatives

Diphenylimidazole and diphenylthiazole derivatives were synthesized and tested as inhibitors of platelet aggregation in in vitro experiments with the rabbit. Diphenylthiazole derivatives (10) were more potent than diphenylimidazole derivatives (4) in inhibiting arachidonic acid-induced platelet aggregation of rabbit platelet-rich plasma. Two diphenylimidazole and eight diphenylthiazole derivatives were evaluated for ex vivo arachidonic acid and collagen-induced platelet aggregation inhibitory activity using guinea pigs. In these compounds, 4,5-bis(4-methoxyphenyl)-2-(1,5-dimethyl-2-pyrrolyl)thiazole (10n) showed strong activity in vitro and ex vivo. The ex vivo activity of 10n was 200 times stronger than that of aspirin. The mechanism of the activity of 10n was the inhibition of cyclo-oxygenase.     

Synthesis and Cytotoxic and Antiplatelet Activities of Dibenzofuran‐ and Carbazole‐Substituted Oximes

The dibenzofuran‐ and carbazole‐substituted oximes or methyloximes 5 – 10 were prepared and evaluated for their cytotoxic and antiplatelet activities. These compounds were synthesized via alkylation of dibenzofuran‐2‐ol or 9H‐carbazol‐2‐ol with α‐halocarbonyl reagents, followed by reaction with NH₂OH or NH₂OMe (Scheme). A preliminary anticancer assay indicated that the oxime‐type dibenzofuran derivatives 5 and 7a – d are active, while the corresponding oxime ethers 9b and 9c are inactive at the same concentration. Therefore, a H‐bond‐donating group seems to be crucial for cytotoxicity. Among the compounds tested, 2‐[(dibenzo[b,d]furan‐2‐yl)oxy]‐1‐(4‐methoxyphenyl)ethan‐1‐one O‐methyloxime ( 9c ) exhibited potent inhibitory activity against platelet aggregation induced by arachidonic acid, with an IC₅₀ value of 14.87 μM , without being cytotoxic at a concentration of 100 μM .     

The first total synthesis of the (±)-17-methyl-trans-4,5-methyleneoctadecanoic acid and related analogs with antileishmanial activity

The first total synthesis of the marine cyclopropane fatty acid (±)-17-methyl-trans-4,5-methyleneoctadecanoic acid was accomplished in eight steps and in 9.1% overall yield starting from 1-bromo-12-methyltridecane. The cis analog (±)-17-methyl-cis-4,5-methyleneoctadecanoic acid was also synthesized but in seven steps and in 16.4% overall yield. With the two isomeric cyclopropane fatty acids at hand it was possible to unequivocally corroborate the trans relative configuration of the naturally occurring fatty acid by gas chromatographic co-elution of the corresponding methyl esters. The cis isomer was cytotoxic to Leishmania donovani promastigotes with an IC₅₀ of 300.2 ± 4.2 μM.     

A new flavane acid from the fruits of Illicium verum

A new compound, illiciumflavane acid (1), along with 13 known compounds (2–14), were isolated from the fruits of Illicium verum Hook. F. Their structures were elucidated through various spectroscopic methods, including 1D NMR (¹H NMR, ¹³C NMR), 2D NMR (HMQC, HMBC and NOESY) and HRMS. The stereochemistry at the chiral centres was determined using CD spectrum as well as analyses of coupling constants and optical rotation data. Cytotoxicity evaluation of four compounds showed that illiciumflavane acid and (E)-1,2-bis(4-methoxyphenyl)ethene exhibited potential against A549 activities with IC₅₀ values of 4.63 μM and 9.17 μM, respectively.