Thiourea Groups Research Articles

Cholic acid-based high sensitivity fluorescent sensor for α,ω-dicarboxylate: an intramolecular excimer emission quenched by complexation

Fluorescent receptors ( 1 and 2) bearing two binding units on C3 and C24 and two signal display units on C7 and C12 of cholic acid, respectively, were designed and synthesized. Both 1 and 2 emit a much weaker fluorescence than that of the control compound 3 lacking of the binding units reflecting that a PET process originated from the C-3 thiourea group to the plural pyrenyl pendant groups is operative. Addition of terminal dicarboxylate anions to the CH 3CN solution of 1 or 2 enhances the PET process, which leads to a significant and highly sensitive fluorescence response, resulting in an almost complete quenching of the excimer emission of the signal units. To maximize the interaction of the host and the guest, carboxylates of more than five carbon chains could penetrate through the space between the two pyrenyl pendants of the host, triggering a considerable conformational change of the fluorophores. As a result, an enhancement of the monomer emission at the expense of the excimer emission will take place. The binding properties and mechanism of 1 and 2 to dicarboxylates in CH 3CN were manifested by the combined fluorescence, UV–vis, and 1H NMR spectroscopic method.

Design, Synthesis, and Evaluation of Enhanced DNA Binding New Lipopolythioureas

Nonviral gene delivery is limited to a large extent by the cationic nature of most of the chemical vector. We have shown that lipopolythioureas interact with DNA. However, lipopolythioureas were not very efficient at transfecting cells, probably due to reduced interaction between the noncationic synthetic lipid and the cell membrane. Here, we report that liposomes made from a new thiourea lipid, DPPC, and a lipid bearing an RGD ligand allowed very efficient entry of the lipopolythioureas into integrin alpha(v)beta(3) expressing cells. In addition, we show that a stable interaction between DNA and lipopolythiourea could be obtain with two thiourea groups. Moreover, the addition of a hydrophilic terminus improves the formulation of these new DNA binding agents.

Carboxyester functionalised dye–zeolite L host–guest materials

A procedure for the selective modification of zeolite L channel ends with carboxyl terminated groups is reported. The material was prepared by first grafting organic molecules with a terminal amino group to the channel openings. These were afterwards reacted with the thiourea group of methyl-3-isothiocyanatopropionate. The success of the reaction was tested by means of vibrational spectroscopy, optical microscopy and energy transfer experiments after binding strongly luminescent dyes to the carboxyl groups. The reaction was successfully carried out on 5000 nm and 30 nm sized crystals.

Toward the control of Leptosphaeria maculans: Design, syntheses, biological activity, and metabolism of potential detoxification inhibitors of the crucifer phytoalexin brassinin

Brassinin ( 1), a crucial plant defense produced by crucifers, is detoxified by the phytopathogenic fungus Leptosphaeria maculans ( Phoma lingam) to indole-3-carboxaldehyde using a putative brassinin oxidase. Potential inhibitors of brassinin detoxification were designed by replacement of its dithiocarbamate group (toxophore) with carbamate, dithiocarbonate, urea, thiourea, sulfamide, sulfonamide, dithiocarbazate, amide, and ester functional groups. In addition, the indolyl moiety was substituted for naphthalenyl and phenyl. The syntheses and chemical characterization of these potential detoxification inhibitors, along with their antifungal and cytotoxic activity, as well as screening using cultures of L. maculans are reported. Overall, three types of interaction were observed in cultures of L. maculans co-incubated with the potential inhibitors and brassinin: (1) a decrease on the rate of brassinin detoxification due to the strong inhibitory activity of the compound on fungal growth, (2) a decrease on the rate of brassinin detoxification due to the inhibitory activity of the compound on the putative brassinin oxidase, and (3) a low to no detectable effect on the rate of brassinin detoxification. A noticeable decrease in the rate of brassinin detoxification was observed in the presence of N′-methylbrassinin, methyl N-methyl- N-(naphthalen-2-ylmethyl) dithiocarbamate, tryptophol dithiocarbonate, and methyl 3-phenyldithiocarbazate. Tryptophol dithiocarbonate appeared to be the best inhibitor among the designed compounds, representing the first inhibitor of brassinin detoxification and potentially the first selective protecting agent of oilseed crucifers against L. maculans infestation.

The Synthesis and Structure of Linear and Dendritic Thiourea‐Linked Glycooligomers.

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Synthesis and Biological Activity of Novel (E,E)-vic-dioximes

A novel vic-dioxime ligand containing the thiourea group, (4E,5E)-1,3-bis{4-[(4-methylphenylamino)methyl] phenyl}- 2-thiooxaimidazoline-4,5-dione dioxime, (4) mmdH2 has been prepared from N,N′-bis{4-[(4-methylphenylamino)methyl]phenyl}thiourea, (3) mft and cyanogen di-N-oxide. Mononuclear [M(mmdH)2], where M = NiII, CoII and CuII complexes of the (4) mmdH2 bidentate ligand have been obtained with a 1:2 metal:ligand ratio, as do most the vic-dioximes. The complexes are formed by coordination of N, N atoms of the ligand. The vic-dioxime ligand and its some transition metal complexes have been characterized by elemental analyses, molar conductance data, magnetic susceptibility, i.r., 1H-n.m.r and u.v.–vis. spectroscopy. Conductivity measurements have shown that mononuclear complexes are non-electrolytes. In addition, the ligands and metal complexes were screened for antibacterial and antifungal activities by agar well diffusion techniques using DMF as solvent.

Two Multi‐armed Neutral Receptors for α,ω‐Dicarboxylate Anions

AbstractTwo new multi‐armed neutral receptors 1 and 2 containing thiourea and amide groups were synthesized by simple steps in good yields. Receptors 1 and 2 have a better selectivity and higher association constants for malonate anion than other anions examined by the present work. In particular, distinct color changes were observed upon addition of dicarboxylate anions to the solution of 1 in DMSO. The UV‐Vis and fluorescence spectra data indicate that a 1:2 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of shorter carbon chain, and a 1:1 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of longer carbon chain through hydrogen bonding interactions.

UV–vis and fluorescence spectroscopic detection of anions by the conformational restriction of 2,2′-binaphthalene derivatives bearing thiourea groups through a methylene spacer

Novel fluorescence receptors, 2 and 3 based on 2,2′-binaphthalene possessing thiourea moieties via a methylene spacer have been synthesized. Hydrogen bonds of NH groups of thiourea moieties with acetate anion were confirmed by 1H NMR study in MeCN- d 3. These receptors showed characteristic UV–vis spectral changes through isosbestic points on complexation with anions inspite of lacking conjugation between the chromophore and the binding sites in polar organic solvent such as acetonitrile. The UV–vis spectral changes arise from the conformational restriction of the 2,2′-binaphthyl skeleton on the complexation. The receptors exhibit high selectivities for AcO − and F −. The fluorescence intensity of the receptors decreases with the increasing amount of the AcO −, however, addition of F − induces a different change in its fluorescence spectrum, in which shorter emission of the receptors decreases with the increase in F − concentration, while the longer emission of the receptors increases through an isoemissive point in MeCN. The results suggest that favorable dual-wavelength ratiometric fluorescence measurement can be conducted by the receptors for F −.

Anthracene derivatives bearing thiourea group as fluoride selective fluorescent and colorimetric chemosensors

New anthracene derivatives bearing thiourea group have been synthesized and characterized including X-ray crystallography. These chemosensors display selective ratiometric changes in their fluorescence spectra upon the addition of fluoride ion.

Preparation of molecularly imprinted polymers with thiourea group for phosphate

Molecularly imprinted polymers selective for phosphate were prepared with the two types of functional monomers, 1-allyl-2-thiourea and N-methyl- N′-(4-vinylphenyl)-thiourea, and the binding abilities of the polymers were evaluated. Phenylphosphonic acid or diphenyl phosphate were used as the template molecules and the imprinted polymers prepared with 1-allyl-2-thiourea as functional monomer showed high binding ability to phosphate in aqueous media and nearly 90% of phosphate could be recovered. Also, the imprinted polymer prepared with N-methyl- N′-(4-vinylphenyl)-thiourea as functional monomer had a high binding ability and specific interaction with phosphate in acetonitrile solution and over 90% of phosphate-derivatives could be recovered selectively.

Identification of Potent and Selective Inhibitors of PDGF Receptor Autophosphorylation

We report the structure-activity relationship of quinoline and quinazoline derivatives, which include urea, thiourea, urethane, and acylthiourea groups, as inhibitors of the platelet-derived growth factor (PDGF) receptor autophosphorylation. Our previous studies showed that the quinoline and quinazoline derivatives including urea, thiourea, and carbamate groups were highly potent compounds as the PDGF receptor autophosphorylation inhibitor, but these compounds did not exhibit receptor selectivity between the PDGF receptor and the c-kit receptor. As a result of further synthesis and biological evaluation, we have found that the quinoline and quinazoline-acylthiourea derivatives showed not only good inhibitory activity for the PDGF receptor but also receptor selectivity between the PDGF receptor and the c-kit receptor. Furthermore N-{4-[(6,7-dimethoxy-4-quinolyl)oxy]phenyl}-N'-(2-methylbenzoyl)thiourea exhibited potent oral efficacy in in vivo assay using the rat carotid balloon injury model. Therefore, the quinoline and quinazoline-acylthiourea derivatives may be expected to have potential as therapeutic agents for the treatment of restenosis.

Quantum-Chemical Design of Cryptand-like Ditopic Salt Binders.

Hartree-Fock, density functional, and MP2 methods are applied to the problem of designing neutral, bicyclic C3-symmetric cages incorporating interacting anion- and cation-binding sites which strongly bind NaCl as an ion contact pair. A large number of trial ligands L and their complexes L:NaCl are tested, with the focus on maximizing binding by (i) optimizing the cavity size and shape and (ii) varying the nature of the anion- and cation-binding functionalities. The corresponding complexes L:Cl(-) and L:Na(+) are also studied in some detail. An analysis of their structures and charge distributions helps to build a consistent picture of the requirements for a successful NaCl binding. The 'best' candidate ligand utilizes a tripodal triether-substituted amine N(CH2CH2OR-)3 to bind the sodium cation; three thiourea groups in a tripodal arrangement with a 1,3,5-trisubstituted benzyl spacer group {C6H3(CH2NHC [Formula: see text] XNH-)3 X=O,S} to bind chloride; and a -CH2CH2- spacer linking the two binding sites. A simple Quantitative Structure-Property analysis suggests that the binding cavity shape and size is near to the optimal one for this system.

Non‐racemic atropisomeric (thio)ureas as neutral enantioselective anion receptors for amino‐acid derivatives: Origin of smaller Kass with thiourea than urea derivatives

The synthesis of a limited series of non-racemic atropisomeric 1-(2-(4-methyl-2-thioxothiazol-3(2H)-yl)phenyl)-3-(hetero)aryl-(thio)ureas is described. Using NMR titration experiments monitoring the shift of the two NH of the (thio)urea and the C-5 hydrogen of the heterocycle, the binding constants for some optically pure (thio)-ureas with the enantiomers of N-protected amino acid tetrabutylammonium salts were determined in CD3CN. The obtained enantioselectivities were modest. Contrary to what was expected on the basis of the NH acidity in thiourea versus urea group, the association constants were smaller with the thiourea than with the corresponding urea. X-ray data, DFT calculations, and NMR provided the explanation of that unexpected behavior: the urea presents a pre-organized (Z,Z) conformation suitable for a double hydrogen bond with the carboxylate anion, the thiourea presents a (Z,E) conformation, which must be reorganized in a constrained (Z,Z) conformation in the complex. An intramolecular hydrogen bond between one NH and the thiocarbonyl group of the heterocycle, which is present in the thiourea and absent in the urea, might also contribute to the smaller K(ass) for the thiourea. The possible implication of these observations in the field of bifunctional organocatalysis is briefly discussed.

Synthesis of colorimetric receptors for dicarboxylate anions: a unique color change for malonate

Three new chromogenic receptors ( 1 , 2 , and 3 ) containing p-nitrophenyl or p-nitronaphthyl or methyl groups appended to the thiourea groups were synthesized and characterized. Upon addition of a series of dicarboxylate anions to receptor 1 in DMSO, only the appearance of the solution of receptor 1 with malonate showed a color change from blue to yellow which can be detected by the naked eye at parts per million. With the addition of the series of dicarboxylate anions to receptor 2 , the solutions showed an indistinct intense dark-red color. Whereas the addition of the same dicarboxylate anions to receptor 3 , the solutions did not induce any color change. Thus, for the unique color change, the receptor 1 can act as an optical chemosensor for the malonate anion even in the presence of other dicarboxylate anions.

The Synthesis and Structure of Linear and Dendritic Thiourea‐Linked Glycooligomers

AbstractAn efficient strategy to produce unnatural glycooligomers containing thiourea intersaccharide bridges has been developed. The presence of the thiourea groups in these oligomers should promote the association with polyphosphates, including nucleic acids, due to the hydrogen‐bonding capabilities of the thioureas. Moreover, glycooligomers built from thiourea groups should form complex secondary and tertiary structures due to the interplay of hydrogen bonding and rotational restriction at the bonds adjacent to thiocarbonyl groups. Herein, the preparation and conformational properties of both linear and dendritic architectures are described. This synthetic method relies on the coupling of peracetylated azidoglycosyl isothiocyanates and fully unprotected amine‐functionalised growing oligomers. Deacetylation of the hemiacetylated thiourea adduct and reduction of the azido groups allow entry into a new coupling cycle. The procedure is quite general, should be easily extended to molecular diversity‐oriented and solid‐phase approaches and will allow the investigation of intermolecular interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis, Characterization, and Luminescence Properties of a New Series of Eu3+-Containing Macrocycles

The synthesis and structural characterization of a series of neutral Eu(3+)-containing macrocyclic complexes, Eu(4)-Eu(7), are reported. The synthetic pathway herein allows for the size and functionality of the macrocycle to be tailored in one step from a common precursor (N,N' '-bis(p-isothiocyanatobenzylcarbamoylmethyl)diethylenetriamine-N,N'N' '-triacetic acid, (3) in high yield. The macrocyclic ligands 4-7 have within their structure a bis-amide derivative of diethylenetriaminepentaacetic acid (DTPA) functioning as the europium chelate that is bridged through thiourea groups by either a butyl (4), hexyl (5), octyl (6), or m-benzyl (7) linker. The two thiourea groups were designed into the host macrocycle to serve as hydrogen-bond donors to potential guest molecules that may alter the luminescence properties of the parent macrocycle. Characterization of the luminescence of Eu(4)-Eu(7) reveals an antenna effect from the ligand, and the luminescence lifetime data reveals the presence of one coordinated water molecule in aqueous solution.

Guanidine‐Thiourea Bifunctional Organocatalyst for the Asymmetric Henry (Nitroaldol) Reaction

AbstractNovel bifunctional catalysts having guanidine and thiourea functional groups were developed for the asymmetric Henry (nitroaldol) reaction. Various structural developments of the catalyst revealed that the compound having an octadecyl‐substituted guanidine and thiourea groups linked with a chiral spacer derived from phenylalanine, i.e., 1e, efficiently promoted the Henry reaction. This bifunctional organocatalyst 1e also gave high asymmetric inductions with aliphatic cyclic aldehydes and branched aliphatic aldehydes (82–90% ee).

Visible and FTIR Microscopic Observation of Bisthiourea Ionophore Aggregates in Ion-Selective Electrode Membranes

Since conventional response models for ionophore-based ISEs are based on the assumption of a homogeneous membrane phase, they cannot accurately predict the response of membranes containing self-aggregating ionophores. However, meaningful conclusions about the relationship between ionophore structure and potentiometric responses can only be drawn if ionophore aggregation is properly recognized. This study demonstrates that dark field visible microscopy and FTIR microspectroscopy are valuable tools for the observation of such ionophore self-aggregation and, thereby, the development of new ionophore-based ISEs. Sulfate selective electrodes with solvent polymeric membranes containing bisthiourea ionophores that differ only by peripheral nonpolar substituents were shown to exhibit very different interferences from the sample pH. On one hand, optimized electrodes based on an ionophore with a phenyl substituent on each thiourea group (1) do not respond to pH at all and function well as sulfate-selective electrodes. On the other hand, membranes containing a more lipophilic ionophore with two additional hexyl-substituted adamantyl groups (2) exhibit severe pH interference at pH values as low as pH 5. The observation of membranes containing ionophore 2 with dark field visible microscopy and FTIR microspectroscopy shows supramolecular aggregation, and explains the startling difference between the potentiometric responses of the two types of electrodes.

Asymmetric Michael Addition of Arylthiols to α,β‐Unsaturated Carbonyl Compounds Catalyzed by Bifunctional Organocatalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Redefining the structure–activity relationships of 2,6-methano-3-benzazocines. Part 3: 8-Thiocarboxamido and 8-thioformamido derivatives of cyclazocine

8-Position variants of cyclazocine have been made where the phenolic 8-OH was replaced by thioamide, amidine, guanidine, urea and thiourea groups. High affinity for opioid receptors was observed for the 8-CSNH2 and 8-NHCHS analogues indicating that these groups are isosteric with not only the 8-OH but with the previously synthesized 8-CONH2 and 8-NHCHO cyclazocine derivatives.