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PubMed2004

Synthesis and complete NMR spectral assignment of thiophene-substituted sulfinyl monomers.

This paper describes the synthesis of thiophene-substituted sulfinyl monomers. It comprises a four-step reaction by which the thiophene unit is built in via Suzuki coupling. These monomers could be used as building blocks for the preparation of conducting polymers via a new concept: the sulfinyl precursor route i.e. via thiophene substituted poly(p-phenylenevinylene) precursors. Furthermore, the complete 1H and 13C NMR signal assignment is presented. In addition to being essential for the characterization of the polymers concerned, it offers useful input information for further improvement of chemical shift prediction software. Furthermore, the T1C relaxation decay times are demonstrated to have the potential of being a fast and robust criterion for the spectral assignment of analogous monomers.

Journal Article↗
PubMed1984

Metabolic hydroxylation of the thiophene ring: isolation of 5-hydroxy-tienilic acid as the major urinary metabolite of tienilic acid in man and rat.

The metabolism of tienilic acid, a drug containing a thiophene ring, was reinvestigated in man, rat and dog. The major urinary metabolite in man and rat was isolated and completely characterized by comparison with a synthetic compound. This metabolite derives from the hydroxylation of the thiophene ring of tienilic acid in position 5. Its isomers, 3- and 4-hydroxy-tienilic acids, were synthetized but could be detected neither in man nor in rat urine. Because of its particular behaviour toward electrophiles, 5-hydroxy-tienilic acid was found to react with diazomethane with the formation of a complex mixture of methylated products. This made difficult its measurement by a previously described GLC technique, after acidic extraction and methylation by diazomethane. A new very simple assay using HPLC and direct injection of urine is described in this paper. This assay led to a very precise and reproductible determination of tienilic acid and its hydroxylated metabolite in urine. Up to 50% of tienilic acid is excreted in man or rat urine as 5-hydroxy-tienilic acid whereas this metabolite does not appear in dog urine. These data describe the first example of metabolic hydroxylation of the thiophene ring.

Adult↗
PubMed2004

The sonoelectrooxidation of thiophene S-oxides.

Thiophene-S-oxides (thiophene monoxides) are relatively new compounds, less stable than the better-known thiophene-S-dioxides. They are useful as synthons for a range of applications, including in the production of pharmaceuticals. They have interesting photochemical properties, but in this presentation we contrast the electro-oxidative voltammetry of differently substituted derivatives. We also compare carbocyclic compounds such as tetracyclone, the electro-oxidation of which at relatively high potentials has never been reported in silent or insonated conditions.

Journal Article↗
PubMed2001

New 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants.

A series of new 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives were synthesized in an attempt to find a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. Title compounds were evaluated for in vitro activity on 5-HT1A receptor and 5-HT transporter. They show high nanomolar affinity for both activities, and in particular, compounds 1-(5-chlorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (7) and 1-(5-fluorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (8) show values (nM) of K(i)=30 and 2.3 for 5-HT1A receptors and K(i)=30 and 12 for serotonin transporters, respectively. In GTPgammaS binding assays, compound 8 revealed antagonist properties to 5-HT1A receptors. Such a pharmacological profile could lead to potent antidepressant agents with new dual mechanism of action.

Animals↗
PubMed2003

Synthesis, spectral studies and screening for amoebicidal activity of new palladium(II) complexes derived from thiophene-2-carboxaldehyde thiosemicarbazones.

In view of the antiamoebic properties observed for many thiophene-2-carboxaldehyde thiosemicarbazones, a series of N(4)-substituted thiosemicarbazones metal complexes derived from thiophene-2-carboxaldehyde was prepared for evaluation against Entamoeba histolytica. Reaction of thiophene-2-carboxaldehyde with cycloalkylaminothiocarbonylhydrazines having different amines gave the corresponding thiosemicarbazones. Reaction of latter with [Pd(DMSO)(2)Cl(2)] gave requisite palladium thiosemicarbazone complexes of the type [Pd(TSC)Cl(2)] (where TSC=thiosemicarbazones). Screening of antiamoebic activity of these compounds was assayed in vitro against (HM-1:1MSS) strain of E. histolytica. Enhancement of antiamoebic resulted from introducing palladium metal in the thiosemicarbazone moiety. Among the studied compounds, [Pd(2-TCA-1,2,3,4-THQTSC)Cl(2)] (2a) showed better activity.

Amebicides↗
PubMed1999

N'-[2-(2-thiophene)ethyl]-N'-[2-(5-bromopyridyl)] thiourea as a potent inhibitor of NNI-resistant and multidrug-resistant human immunodeficiency virus-1.

The thiophene-ethyl thiourea (TET) compound N'-[2-(2-thiophene)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea (compound HI-443) was five times more potent than trovirdine, 1250 times more potent than nevirapine, 100 times more potent than delavirdine, 75 times more potent than MKC-442, and 50 times more potent than AZT against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation. HI-443 was almost as potent against the NNI-resistant HIV-1 strain A17 with a Y181C mutation as it was against HTLV(IIIB). The activity of HI-443 against A17 was ten times more potent than that of trovirdine, 2083 times more potent than that of nevirapine, and 1042 times more potent than that of delavirdine. HI-443 inhibited the replication of the NNI-resistant HIV-1 strain A17 variant with Y181C plus K103N mutations in RT with an IC50 value of 3.3 microM, whereas the IC50 values of trovirdine, nevirapine, and delavirdine were all >100 microM. These findings establish the novel thiophene containing thiourea compound HI-443 as a novel NNI with potent antiviral activity against NNI-sensitive, NNI-resistant and multidrug-resistant strains of HIV-1.

Anti-HIV Agents↗
PubMed2002

Unusual sulfur chemistry in the thermal reaction of sultene and thiophene endoperoxide sulfur donors with cyclic alkynes: reversible formation of a persistent thiirenium ion and trapping of a thiirene by [4 + 2] cycloaddition.

The highly reactive cyclooctyne 2b serves as sulfur acceptor for both sulfur donors, namely the sultene 1A and thiophene endoperoxide 1B to afford sulfur-transfer products. With the acid-activated sultene 1A, the persistent thiirenium ion 3Ab is formed, which has allowed the direct observation of the initial sulfur-transfer adduct. On treatment with base, the thiirenium ion 3Ab reverts quantitatively to the cyclooctyne and sultene, whereas in neutral media it rearranges to the diene 6Ab. The rearrangement to the diene 6Ab, as well as the formation of spirocyclic adduct 6Ac in the reaction with dithiocyclononyne 2c, is proposed to proceed through a carbene mechanism. In the reaction of the cyclooctyne 2b with thiophene endoperoxide 1B, a thiirene is formed through sulfur transfer by an intermediary oxathiirane derived from the thiophene endoperoxide; as final product, the episulfide (R*,R*,R*)-3Bb is produced diastereoselectively by immediate [4 + 2] cycloaddition of the thiirene with the heterodiene 4B.

Journal Article↗
PubMed2003

Easily processable phenylene-thiophene-based organic field-effect transistors and solution-fabricated nonvolatile transistor memory elements.

The synthesis of a new series of mixed phenylene-thiophene oligomers is reported; 2,5-bis(4-n-hexylphenyl)thiophene (dH-PTP, 1), 5,5'-bis(4-n-hexylphenyl)-2,2'-bithiophene (dH-PTTP, 2), 5,5' '-bis(4-n-hexylphenyl)-2,2':5',2' '-terthiophene (dH-PT(3)P, 3), 5,5' "-bis(4-n-hexylphenyl)-2,2':5',2' ':5' ',2' "-quaterthiophene (dH-PT(4)P, 4), 1,4-bis[5-(4-n-hexylphenyl)-2-thienyl]benzene (dH-PTPTP, 5), and 2,5-bis[4(4'-n-hexylphenyl)phenyl]thiophene (dH-PPTPP, 6) were characterized by (1)H NMR, elemental analysis, UV-visible spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Vacuum-evaporated and solution-cast films were characterized by X-ray diffraction and scanning electron microscopy. All compounds display high p-type carrier mobilities as evaporated (up to 0.09 cm(2)/Vs) and as solution-cast (up to 0.03 cm(2)/Vs) films on both Si/SiO(2) and ITO/GR (glass resin) substrates. The straightforwardly synthesized dH-PTTP (2) displays an unprecedented combination of mobility, on/off ratio, stability, and processability. Both dH-PTTP (2) and dH-PPTPP (6) display a reversible, tunable, and stable memory effect even as solution-cast devices, with turn-on characteristics shifting from accumulation mode to zero or depletion mode after a writing voltage V(w) is applied. The charge storage is distributed over the gate dielectric structure and is concentrated near the dielectric-semiconductor interface, as evidenced by the response of "floating gate" configuration devices. Simple nonvolatile elements have been fabricated by solution-only techniques on ITO substrates using spin-coated glass resin, solution-cast oligomeric semiconductors, and painted graphite paste electrodes.

Journal Article↗
PubMed2002

Design and synthesis of push-pull chromophores for second-order nonlinear optics derived from rigidified thiophene-based pi-conjugating spacers.

Two series of push-pull chromophores built around thiophene-based pi-conjugating spacers rigidified either by covalent bonds or by noncovalent intramolecular interactions have been synthesized and characterized by UV-vis spectroscopy, electric field induced second harmonic generation (EFISH) and differential scanning calorimetry. Comparison of the linear and second-order nonlinear optical properties of chromophores based on a covalently bridged dithienylethylene (DTE) spacer with those of their analogues based on open chain DTE shows that the rigidification of the spacer produces a considerable bathochromic shift of the absorption maximum together with a dramatic enhancement of the molecular quadratic hyperpolarizability (mu beta) which reaches values among the highest reported so far. A second series of NLO-phores has been derived from a 2,2'-bi(3,4-ethylenedioxythiophene) (BEDOT) pi-conjugating spacer. As indicated by X-ray and UV-vis data, rigidification of the spacer originates in that case, from noncovalent intramolecular interactions between sulfur and oxygen atoms. Again, comparison with the parent compounds based on an unsubstituted bithiophene spacer reveals a marked red shift of the absorption maximum and a large enhancement of mu beta. In an attempt to distinguish the contribution of the electronic and geometrical effects of the ethylenedioxy group, a third series of NLO-phores based on 3,4-ethylenedioxythiophene (EDOT) and 3,4-dihexyloxythiophene spacers has been synthesized. Comparison with compounds based on unsubstituted thiophene shows that, despite a red shift of lambda(max), introduction of alkoxy groups leads to a decrease of mu beta. Theoretical calculations indicate that this effect results from a decrease of the dipole moment (mu) caused by the auxiliary electron-donor alkoxy groups on the thiophene ring. In contrast, replacement of BT by BEDOT produces an increase of mu, which associated with the noncovalent rigidification of the BT system accounts for the observed enhancement of mu beta.

Journal Article↗
PubMed2002

Sulfur-rich heterocycles from 2-metalated benzo[b]thiophene and benzo[b]furan: synthesis and structure.

The reaction of 2-lithiated benzo[b]thiophene with 8 equiv of elemental sulfur was found to give pentathiepino[6,7-b]benzo[d]thiophene. In contrast, treatment of 2-lithiated benzo[b]furan with sulfur under similar conditions produced the interesting ring system bis(benzo[4,5]furo)[2,3-e:3',2'-g][1,2,3,4]tetrathiocine. Both of these new cyclic polysulfides were studied by X-ray crystallography. Two polymorphic forms of pentathiepino[6,7-b]benzo[d]thiophene were found, displaying similar conformations but different packing schemes, which was also evident from powder diffraction data.

Journal Article↗
PubMed2006

Intramolecular thia-anti-Michael addition of a sulfur anion to enones: a regiospecific approach to multisubstituted thiophene derivatives.

The intramolecular thia-anti-Michael addition starting from readily available alpha-alkenoyl-alpha'-carbamoyl ketene-(S,S)-acetals 1 containing a 1,3-dithiolane moiety was developed. In particular, in the presence of aliphatic primary amines, a series of tetrasubstituted thiophene derivatives, 2-(alkylamino)-5-alkyl-4-hydroxythiophene-3-carboxamides 2, were synthesized via tandem fragmentation, substitution, and intramolecular thia-anti-Michael addition reactions of 1, where amine played the dual roles of a base and a nucleophile. The intramolecular thia-anti-Michael addition, as the key step, proceeded in a regiospecific manner and showed a general scope to the beta-substituents of enones 1. A possible mechanism for the formation of the multisubstituted thiophenes was proposed. By this research, a new and efficient route to various tetrasubstituted thiophene derivatives was created.

Journal Article↗
PubMed1998

Characterization and Synthesis of a 6-Substituted Benzo[b]thiophene.

An impurity observed during the synthesis of zileuton (Zyflo) has been isolated and characterized as a benzo[b]thiophene derivative that has undergone electrophilic substitution in the 6 position (4). A nine-step synthesis confirms the structural assignment. Key steps in the synthesis include a regioselective Friedel-Crafts coupling between 2-hydroxythioanisole, 8, and 1-(benzo[b]thien-2-yl)ethanol, 1, and formation of a benzo[b]thiophene from an o-methylthiobenzaldehyde, 14, and chloroacetone. The synthesis provides a potentially general route to substituted benzo[b]thiophenes.

Journal Article↗
PubMed2006

Thiophene adsorption and activation on MoP(001), gamma-Mo2N(100), and Ni2P(001): density functional theory studies.

The adsorption and dissociation of thiophene on the MoP(001), gamma-Mo(2)N(100), and Ni(2)P(001) surfaces have been computed by using the density functional theory method. It is found that thiophene adsorbs dissociatively on MoP(001), while nondissociatively on gamma-Mo(2)N(100) and Ni(2)P(001). On MoP(001), the dissociation of the C-S bonds is favored both thermodynamically and kinetically, while the break of the first C-S bond on gamma-Mo(2)N(100) has an energy barrier of 1.58 eV and is endothermic by 0.73 eV. On Ni(2)P(001) there are Ni(3)P(2)- and Ni(3)P-terminated surfaces. On the Ni(3)P(2)-terminated surface, the dissociation of the C-S bonds of adsorbed thiophene is endothermic, while it is exothermic on the Ni(3)P-terminated surface.

Journal Article↗
PubMed1995

Isolation and Characterization of Mutants of Thiophene Synthesis in Tagetes erecta.

Two mutants of Tagetes erecta displaying aberrant thiophene composition were identified by screening more than 300 plants from a mutagenized M2 population using high-performance liquid chromatography analysis of root extracts. Both mutants, which may have originated from the same mutational event, contained high amounts of the C13 monothiophene 2-(but-3-en-1-ynyl)-5-(penta-1,3-diynyl)-thiophene that was previously not found in T. erecta and also high amounts of two C13 bithienyls that were absent or present at low concentrations in the wild type. The mutant phenotype was also expressed in 21 Agrobacterium rhizogenes transformed root clones derived from both mutants. Feeding experiments with root cultures derived from one mutant and from the wild type indicated that the monothiophene accumulating in the mutant is the common precursor for all bithienyl thiophenes in wild-type and mutant Tagetes erecta. These experiments also showed that one mutant is deficient in demethylation of the monothiophene.

Journal Article↗
PubMed1994

Microbially Mediated Formation of Benzonaphthothiophenes from Benzo[b]thiophenes.

Studies of the microbial metabolism of benzo[b]thiophene (molecular weight 134) by three Pseudomonas isolates showed the formation of benzothiophene sulfoxide, benzothiophene sulfone, and a sulfur-containing metabolite with a molecular weight of 234. Desulfurization of the high-molecular-weight product with nickel boride gave 1-phenylnaphthalene, indicating that the metabolite was benzo[b]naphtho[1,2-d]thiophene. Similarly, the isolates were capable of producing the analogous dimethyl-substituted benzonaphthothiophenes from methylbenzothiophenes that had the methyl substitution on the benzene ring. The formation of benzo[b] naphtho[1,2-d]thiophene was also observed when a petroleum-degrading mixed culture was incubated with benzothiophene-supplemented Prudhoe Bay crude oil. Investigations into the mechanism of formation of these high-molecular-weight compounds showed that they resulted from an abiotic, Diels-Alder-type condensation of two molecules of the sulfoxide, which were microbially produced from the respective benzothiophene, with the subsequent loss of two atoms of hydrogen and oxygen and one atom of sulfur. The condensation products also formed from the sulfoxides of benzothiophene and methylbenzothiophenes when the sulfoxides were enzymatically synthesized by oxidation of the benzothiophene with horse heart cytochrome c and H(2)O(2).

Journal Article↗
PubMed1999

Molecular structure of 5-methyl thiophene acryloyl ethyl thiolester: a vibrational spectroscopic and density functional theory study.

Enzyme-substrate intermediates involving the acyl group 5-methyl thiophene acryloyl (5-MTA) bound to the active site of an enzyme via a sulfur or selenium atom have been characterized by Raman spectroscopy (e.g., J. D. Doran and P. R. Carey, Biochemistry 1996, 35, 12495-12502, and M. J. O'Connor et al., J Amer Chem Soc 1996, 118, 239-240). Raman difference spectra reveal the Raman spectrum of the acyl group in the active site and, in turn, these can be used to probe acyl group conformation and active site forces and interactions. In order to improve the understanding of the relationship between conformational states and vibrational spectra of 5-MTA thiolesters, calculations based on a density functional theory analysis are undertaken for 5-methyl thiophene acryloyl ethyl ester. The calculations provide the precise geometries and energies of rotomers of 5-MTA ethyl thiolester involving rotational isomerism about the C--C single bonds flanking the ethylenic linkage and the S--C bond linking the ethyl group to the sulfur atom. The calculations also provide the vibrational spectrum for each conformer and these predictions are compared with the experimental Raman an IR data for the thiolester in carbon tetrachloride. Modes are identified that can act as conformational markers for isomerism about the C--C and S--C2H5 single bonds. These findings are used to identify the two conformational states giving rise to the Raman spectrum of the 5-MTA-S-enzyme formed by the viral cysteine protease HAV-3C.

Acrylates↗
PubMed1985

Inhibition of thromboxane and 12-HPETE formation by dazoxiben and its two thiophenic acid-substituted derivatives.

LG 82-4-00 (5-(2-(1-imidazolyl)-ethoxy)-thiophene-2-carboxylate) and LG 82-4-01 (4-chloro-thiophenic-substituted derivative) were examined for specific inhibition of thromboxane (TX) synthetase. Thromboxane formation was measured by a radioimmunoassay specific for TXB2. In thrombin (0.6 IU/ml)-stimulated, washed human platelet suspensions (WPS) the IC50 (microM) for inhibition of TX formation were 1.1 (LG 82-4-00), 1.3 (LG 82-4-01) and 0.7 (dazoxiben). LG 82-4-00, LG 82-4-01 and dazoxiben also inhibited collagen (0.6-2.5 micrograms/ml)-induced TXB2 formation and platelet aggregation in human platelet-rich plasma. Neither LG 82-4-00 nor LG 82-4-01 had vasoconstrictor, proaggregatory or TX antagonistic activity or affected primary wave ADP aggregation. There was less than 10% inhibition of PGI2 formation from bovine coronary artery slices with concentrations up to 100 microM. At 100 microM, dazoxiben inhibited thrombin-induced 12-HPETE formation in WPS by 81 +/- 10% whereas LG 82-4-00 and LG 82-4-01 were much less active. These data indicate that LG 82-4-00 and LG 82-4-01 are specific inhibitors of thromboxane synthetase in human platelets.

Animals↗
PubMed1995

A behaviorally selective class of thiophene-containing benzodiazepine receptor ligands.

In a continued effort to probe the role of the aromatic rings in classical 1,4-benzodiazepine (BDZ) ligand pharmacology, a series of new thiophene-containing benzodiazepine receptor (BDZR) ligands were synthesized. As a first step in determining the binding profile and selectivity to BDZR functional subtypes, the affinities in two central nervous system (CNS) regions, cerebellum, in which a single 'Type I' BDZR could be labeled; and spinal cord, in which we have previously demonstrated some receptor heterogeneity, were determined. These compounds were also assessed for their compliance with a recently developed three dimensional pharmacophore for recognition and activation of the 'Type I' BDZR, using the techniques of computational chemistry. The computations showed all ligands synthesized fulfilled the minimum requirements for recognition, further validating the current pharmacophore. Using the criteria for activation, the new ligands were all predicted to be agonists at the cerebellar 'Type I' BDZR. Since the compounds showed reasonable affinity, the behavioral profile of one of them at five in vivo endpoints was determined. This compound demonstrated more behavioral selectivity than the typical 1,4-BDZ ligand. While they fulfilled the requirements for agonist activity at the 'Type I' BDZR, these ligands showed significantly greater delocalization in the electron density distribution in the lowest unoccupied molecular orbital (LUMO), so that either aromatic ring could serve as an electron accepting site, not just the one comparable to the more classical BDZR agonist, flunitrazepam. It is possible that the ability of the second ring in the tested compound (5a) to also function as an electron acceptor can affect the recognition and activation of other receptor types leading to the more discriminate behavioral profile of this thiophene analog compared to flunitrazepam.

Animals↗