Isothiocyanate Group Research Articles

Site specificity of metal ions in heterodinuclear complexes derived from an "end-off" compartmental ligand.

A phenol-based "end-off" compartmental ligand, 2-[N-[2-(dimethylamino)ethyl]iminomethyl]-6-[N,N-di(2-pyridylmethyl)aminomethyl]-4-methylphenol (HL), having a bidentate arm and a tridentate arm attached to the 2 and 6 positions of the phenolic ring, has afforded the following heterodinuclear M(a)(II)M(b)(II) complexes: [CuM(L)(AcO)(2)]ClO(4) (M = Mn (1), Fe (2), Co (3), Ni (4), Zn (5)), [ZnM(L)(AcO)(2)]ClO(4) (M = Co (6), Ni (7)), and [CuNi(L)(AcO)(NCS)(2)] (8). 1.MeOH (1'), 2.MeOH (2'), 3.MeOH (3'), 4.MeOH (4'), 5.MeOH (5'), and 7.MeOH (7') are isostructural and have a heterodinuclear core bridged by the phenolic oxygen atom of L(-) and two acetate groups. In 1'-5' the Cu(II) is bound to the bidentate arm and has a square-pyramidal geometry with one acetate oxygen at the apical site. The M(II) is bound to the tridentate arm and has a six-coordinate geometry together with two acetate oxygen atoms. In the case of 7' the Zn is bound to the bidentate arm and the Ni is bound to the tridentate arm. 8.2-PrOH (8') has a dinuclear core bridged by the phenolic oxygen atom of L(-) and one acetate group. The Cu bound to the bidentate arm has a square-pyramidal geometry with an isothiocyanate group at the apical site. The Ni bound to the tridentate arm has a six-coordinate geometry with further coordination of an isothiocyanate group. The site specificity of the metal ions is discussed together with the crystal structure of [Cu(4)(L)(2)(AcO)(3)](ClO(4))(3).H(2)O (9) prepared in this work.

ChemInform Abstract: Vinyl Ethers with Isothiocyanate Group. Part 18. Reaction with Dicarboxylic Acids, an Easy Way to Bisacylals with Isothiocyanate Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Analysis of functionalized polyisobutylenes by capillary SFC, SEC, HPLC, and CGC-MS after fraction collection

An analytical strategy has been developed for analysis of polyisobutylenes partially functionalized with isothiocyanate groups ( $$\bar M_n< 2000g mol^{ - 1} $$ ) by capillary supercritical-fluid chromatography (CSFC), size- exclusion chromatography (SEC), and reversed-phase liquid chromatography (RPLC). Fractions collected from semi-preparative RPLC and SEC were further characterized by capillary GC-MS (gas chromatography coupled with mass spectrometry). Complete characterization of the polymer was achieved by comparing the results obtained from the different techniques. The degree of polymerization and the relative quantity of the different series of macromolecular chains of polyisobutylene were estimated.

The Cruciferous Nitrile Crambene Has Bioactivity Similar to Sulforaphane When Administered to Fischer 344 Rats but Is Far Less Potent in Cell Culture

The anticarcinogenic properties of broccoli are believed to be due to modification of detoxification enzymes by a group of isothiocyanates, hydrolysis products of glucosinolates, particularly sulforaphane. We previously showed that the nitrile crambene (1-cyano-2-hydroxy-3-butene), present in most Brassica vegetables, induces hepatic quinone reductase activity when administered to rats. In this study, we compared the effects of seven daily oral doses of crambene (50 mg/kg rat/day) and sulforaphane (50 mg/kg rat/day) on induction of hepatic quinone reductase activity in Fischer 344 rats. The two treatments produced similar effects, with crambene and sulforaphane producing 1.5- and 1.7-fold induction in hepatic quinone reductase activity, respectively. Additionally, we evaluated the effect of crambene on quinone reductase activity in Hepa 1c1c7 cells, because this system had been shown to possess high sensitivity to sulforaphane and is commonly used for screening anticarcinogenic compounds. Crambene (5 mM) induced quinone reductase activity and caused cell cycle arrest in the Gsub2;/M phase in mouse Hepa 1c1c7 cells, rat H4IIEC3 cells, and human Hep G2 cells (>95% viability). Doses of crambene needed for induction of quinone reductase in cell culture were ~100-fold greater than effective doses of sulforaphane. These findings indicate that hepatoma cell lines may not accurately reflect relative potency of anticarcinogens in Fischer 344 rats.

Porphyrin, chlorin, and bacteriochlorin isothiocyanates: useful reagents for the synthesis of photoactive bioconjugates.

A novel method for conjugating porphyrins and related molecules to proteins has been developed. The method, which involves synthesizing porphyrins, chlorins, and bacteriochlorins bearing a single amine-reactive isothiocyanate group represents a facile system for protein labeling with these photoactive species. Problems associated with the noncovalent binding of porphyrins to proteins are highlighted, and a method for purifying conjugates to yield exclusively covalently bound porphyrin protein species is demonstrated. Biological activity of porphyrin-bovine serum albumin conjugates formed and purified by these methods is demonstrated using laser scanning confocal microscopy.

Detection of charge movements in ion pumps by a family of styryl dyes.

A family of fluorescent styryl dyes was synthesized to apply them as probes that monitor the ion-translocating activity of the Na,K-ATPase and the SR Ca-ATPase, similar to the widely used dye RH421. All dyes had the same chromophore but they differed in the length of the spacer between chromophore and polar head, an isothiocyanate group, and in the lengths of the two identical acyl chains, which form the tail of the dye molecules. A number of substrate-dependent partial reactions of both P-type ATPases affected the fluorescence intensity, and the magnitude of the fluorescence changes was used to characterize the usefulness of the dyes for further application. The experimental results indicate that electrochromy is the major mechanism of these dyes. While in the case of the Na,K-ATPase a single dye, 5QITC, showed larger fluorescence changes than all others, in the case of the SR Ca-ATPase all dyes tested were almost equal in their fluorescence responses. This prominent difference is interpreted as a hint that the position of the ion binding sites in both ion pumps may differ significantly despite their otherwise closely related structural features. Quench experiments with spin-labeled lipids in various positions of their fatty acids were used to gain information on the depth of the chromophore of the different dyes within the membrane dielectric, however, the spatial resolution was so poor that only qualitative information on the position of the chromophore in the lipid phase could be obtained.

Vinyl Ethers with Isothiocyanate Group: XIX. Reaction with Dicarboxylic Acids: a Simple Route to N,N'-Bis[(2-vinyloxy)ethyl]amides

Reactions of 2-(vinyloxy)ethyl isothiocyanate with dicarboxylic acids (malonic, succinic, glutaric, adipic, pimelic, sebacic acids) under nucleophilic conditions (10-15 wt% of Et3N, 55-80°C, 5-50 min) yield quantitatively N,N`-bis[(2-vinyloxy)ethyl]amides.

Cyclocondensation of 1-Tosyl-2,2-dichloroethenyl Isothiocyanate with O-, S-, N-, and C-Nucleophiles

Treatment of 1-tosyl-2,2-dichloroethenyl isothiocyanate with alcohols, thiols, primary and secondary amines, hydrazine and its derivatives, and phosphonium ylides results in addition of the O-, S-, N-, or C-nucleophilic center to the isothiocyanate group, followed by cyclocondensation with elimination of hydrogen chloride and formation of the corresponding 2-functionally substituted 4-tosyl-5-chloro-1,3-thiazoles. Further transformations of these compounds were studied, and a series of previously unknown types of 3-functionally substituted 1,3-thiazole derivatives were prepared.

First Examples of Luminescent Cyclometalated Iridium(III) Complexes as Labeling Reagents for Biological Substrates

The syntheses, and photophysical and electrochemical properties of the three luminescent cyclometalated iridium(III) complexes [Ir(ppy)2(phen-NCS)](PF6) (1), [Ir(ppy)2(phen-NHCOCH2I)](PF6) (2), and [Ir(ppy)2(phen-NH2)](PF6) (3) (ppy- = 2-phenylpyridinate anion, phen-NCS = 5-isothiocyanato-1,10-phenanthroline, phen-NHCOCH2I = 5-(iodoacetamido)-1,10-phenanthroline, phen-NH2 = 5-amino-1,10-phenanthroline) are reported. Since the isothiocyanate and iodoacetamide groups can react with the primary amine and sulfhydryl groups of biomolecules, respectively, complexes 1 and 2 have been used to label amine- or sulfhydryl-modified oligonucleotides, and human serum albumin, to give luminescent bioconjugates.

ChemInform Abstract: Vinyl Ethers Containing Isothiocyanate Group. Part 16. Synthesis of 2‐(Vinyloxy)ethyl‐ and Allylthioamides and Thioimidates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Arylisothiocyanate-Containing esters of caffeic acid designed as affinity ligands for HIV-1 integrase

Integrase is an enzyme found in human immunodeficiency virus, which is required for the viral life cycle, yet has no human cellular homologue. For this reason, HIV integrase (IN) has become an important target for the development of new AIDS therapeutics. Irreversible affinity ligands have proven to be valuable tools for studying a number of enzyme and protein systems, yet to date there have been no reports of such affinity ligands for the study of IN. As an initial approach toward irreversible ligand design directed against IN, we appended isothiocyanate functionality onto caffeic acid phenethyl ester (CAPE), a known HIV integrase inhibitor. The choice of isothiocyanate as the reactive functionality, was based on its demonstrated utility in the preparation of affinity ligands directed against a number of other protein targets. Several isomeric CAPE isothiocyanates were prepared to explore the enzyme topography for reactive nitrogen and sulfur nucleophiles vicinal to the enzyme-bound CAPE. The preparation of these CAPE isothiocyanates, required development of new synthetic methodology which employed phenyl thiocarbamates as latent isothiocyanates which could be unmasked near the end of the synthetic sequence. When it was observed that β-mercaptoethanol (β-ME), which is required to maintain the catalytic activity of soluble IN (a F185KC280S mutant), reacted with CAPE isothiocyanate functionality to form the corresponding hydroxyethylthiocarbamate, a variety of mutant IN were examined which did not require the presence of β-ME for catalytic activity. Although in these latter enzymes, CAPE isothiocyanate functionality was presumed to be present and available for acylation by IN nucleophiles, they were equally effective against Cys to Ser mutants. One conclusion of these studies, is that upon binding of CAPE to the integrase, nitrogen or sulfur nucleophiles may not be properly situated in the vicinity of the phenethyl aryl ring to allow reaction with and covalent modification of reactive functionality, such as isothiocyanate groups. The fact that introduction of the isothiocyanate group onto various positions of the phenethyl ring or replacement of the phenyl ring with naphthyl rings, failed to significantly affect inhibitory potency, indicates a degree of insensitivity of this region of the molecule toward structural modification. These findings may be useful in future studies concerned with the development and use of HIV-1 integrase affinity ligands.

Advanced precursors in marine biosynthetic study. Part 2: The biosynthesis of isocyanides and isothiocyanates in the tropical marine sponge Axinyssa n.sp.

The biosynthetic origins of the isocyanide and isothiocyanate groups in 9-isocyanopupukeanane ( 2 ) and 9-isothiocyanatopupukeanane ( 3 ) are investigated by incorporation of [ 14C]-labelled advanced precursors into the sponge Axinyssa n.sp.

Trifunctional biotinylation reagents which contain a radiometal binding chelate and an isothiocy anate group for conjugation with biomolecules

Trifunctional biotinylation reagents which contain a radiometal binding chelate and an isothiocy anate group for conjugation with biomolecules

R(−)‐4‐(3‐Isothiocyanatopyrrolidin‐1‐yl)‐7‐(N,N‐dimethylaminosulfonyl)‐2,1,3‐benzoxadiazole, a fluorescent chiral tagging reagent: sensitive resolution of chiral amines and amino acids by reversed‐phase liquid chromatography

The usefulness of R(-)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole [R(-)-DBD-PyNCS], a fluorescent chiral tagging reagent, for the determination of racemic amines and amino acids, was studied. The reagent reacted with beta-blockers selected as representative secondary amines to produce corresponding fluorescent diastereomers (excitation at 460 nm and emission at 550 nm). The yields of the derivatization reaction were dependent on the stereostructure arround the NH group in beta-blockers. The resulting diastereomers were completely separated with single chromatographic run using linear gradient elutions by reversed-phase chromatography. R(-)-DBD-PyNCS was also applied to the determination of DL-amino acid, considered to be one of the primary amines, in human urine and foodstuffs. DL-amino acids tested equally reacted with the reagent, and the thiocarbamoyl derivatives were separated with an ODS column. The epimerization during the derivatization reaction was negligible judging from the resolution of opposite diastereomers on the chromatogram. The occurence of D-amino acids (D-Ala, D-Ser, D-Asp and/or D-Glu) was identified in the samples tested. The structures and the purities were elucidated with on-line HPLC-MS. The chiral reagent possessing an isothiocyanate group (-NCS) in the structure seems to be applicable to continuous sequential analysis of peptides containing D-amino acids. The thiocarbamoyl derivatives obtained from the reaction with DL-amino acids were converted to thiohydantoins via thiazolinones in acidic medium. The thiohydantoins produced from acidic, basic, neutral, hydroxyl and aromatic amino acids were completely separated with isocratic elutions using acidic mobile phase containing 0.1% TFA. The separations were sufficient for the identification of DL-amino acid in peptide sequences. Although the epimerization during the conversion reaction to thiohydantoins was not avoidable, the descrimination of D- and L-configuration was demonstrated with some commercially available peptides such as beta-lipotropin and [D-Ala2]-deltorphin II. The Edman degaradation method using R(-)-DBD-PyNCS was also adopted to autoanlaysis by gas-phase sequencer. The separation and the detection (UV 254 nm) conditions of the derivatives were used without any change from those for the Edman degradation method using PITC as the tagging reagent. The three DL-amino acid residues (Tyr, Ala and Gly) in [L-Ala2]-leucine-enkephalin and [D-Ala2]-leucine-enkephalin were perfectly identidied with the autoanalysis.

Vinyl Ethers with Isothiocyanate Group: XVIII.2* Reaction with Dicarboxylic Acids, an Easy Way to Bisacylals with Isothiocyanate Groups

Electrophilic reaction between 2-(vinyloxy)ethyl isothiocyanate and aliphatic and aromatic dicarboxylic acids (malonic, succinic, glutaric, sebacic, maleic, and phthalic) affords bisacylals with isothiocyanate groups in quantitative yield. The process is carried out at heating without solvent in the presence of catalytic quantities of trifluoroacetic acid.

Synthesis and Structure of a Tetranuclear Nickel Complex of a 40-Membered Macrocyclic Octaamine-Tetrathiophenolate Ligand

Abstract The syntheses and characterization of tetranuclear Ni complexes [(L2)Ni4][ClO4]4 (3) and [(L2)Ni4(NCS)4] (4) of a 40-membered macrocyclic octaamine-tetrathiophenolate ligand (L2)4- are described. Single-crystal X-ray structure analysis of 4 reveals well-separated molecules of the tetranuclear isothiocyanate complex [(L2) NiII 4(NCS)4]. The four NiII centers are arranged in binuclear [N2Ni(μ2-SR)2NiN2(NCS)2] subunits containing distorted square-planar NiN2S2 and distorted octahedral NiN2S2(NCS)2 sites. The fact that the two isothiocyanate groups at the octahedral Ni site are in trans positions can be ascribed to the large ring size of the macrocycle

Synthesis and evaluation of N,N-dialkyl enkephalin-based affinity labels for delta opioid receptors.

To develop affinity labels for delta opioid receptors based on peptide antagonists, the Phe(4) residues of N,N-dibenzylleucine enkephalin and N,N-diallyl[Aib(2),Aib(3)]leucine enkephalin (ICI-174, 864) were substituted with either Phe(p-NCS) or Phe(p-NHCOCH(2)Br). A general synthetic method was developed for the conversion of small peptide substrates into potential affinity labels. The target peptides were synthesized using Phe(p-NH(2)) and a Boc/Fmoc orthogonal protection strategy which allowed for late functional group conversion of a p-amine group in the peptides to the desired affinity labeling moieties. A key step in the synthesis was the selective deprotection of a Boc group in the presence of a tert-butyl ester using trimethylsilyl trifluoromethanesulfonate (TMS-OTf). The target peptides were evaluated in radioligand binding experiments in Chinese hamster ovary (CHO) cells expressing delta or mu opioid receptors. The delta receptor affinities of the N, N-dibenzylleucine enkephalin analogues were 2.5-10-fold higher than those for the corresponding ICI-174,864 analogues. In general, substitution at the para position of Phe(4) decreased binding affinity at both delta and mu receptors in standard radioligand binding assays; the one exception was N, N-dibenzyl[Phe(p-NCS)(4)]leucine enkephalin (2) which exhibited a 2-fold increase in affinity for delta receptors (IC(50) = 34.9 nM) compared to N,N-dibenzylleucine enkephalin (IC(50) = 78.2 nM). The decreases in mu receptor affinities were greater than in delta receptor affinities so that all of the analogues tested exhibited significantly greater delta receptor selectivity than the unsubstituted parent peptides. Of the target peptides tested, only N, N-dibenzyl[Phe(p-NCS)(4)]leucine enkephalin (2) exhibited wash-resistant inhibition of radioligand binding to delta receptors. To our knowledge, 2 represents the first peptide-based affinity label to utilize an isothiocyanate group as the electrophilic affinity labeling moiety. As a result of this study, enkephalin analogue 2 emerges as a potential affinity label useful for the further study of delta opioid receptors.

RTI-76, an isothiocyanate derivative of a phenyltropane cocaine analog, as a tool for irreversibly inactivating dopamine transporter function in vitro.

Human dopamine transporters, stably expressed by human embryonic kidney-293 cells, were reacted with 3beta-(3p-chlorophenyl)tropan-2beta-carboxylic acid p-isothiocyanatophenylethyl ester (RTI-76) under varying conditions. Exposure to RTI-76 (1 microM) at 0 degrees C, followed by extensive wash-out, reduced subsequent binding of the cocaine analog [3H]2beta-carbomethoxy-3beta-(4-fluorophenyl) tropane (WIN 35,428), which was caused by an increase in Kd in the absence of a Bmax change. Exposure to RTI-76 (50 nM(-1) microM) at 37 degrees C, however, caused concentration-dependent reductions in binding Bmax; increases in Kd were observed only at high levels of RTI-76 (0.5-1 microM). The reductions in Bmax are consonant with acylation of transporters, the increases in Kd with incomplete wash-out observed also for the amine precursor of RTI-76 which lacks the isothiocyanate group for irreversible binding and which did not lower Bmax at 37 degrees C. Reductions in binding Bmax generated by varying concentrations of RTI-76 up to 300 nM at 37 degrees C correlated with reductions in [3H]dopamine uptake Vmax on a one-to-one basis, with Km values showing a tendency towards a small reduction as a function of transporter inactivation, but the potency of WIN 35,428 in inhibiting uptake not showing a change. The results are discussed in the context of possible oligomeric assemblies of dopamine transporters carrying multiple recognition sites for cocaine analogs and dopamine.

A glutathione S-transferase inducer from papaya: rapid screening, identification and structure-activity relationship of isothiocyanates

We have developed a simple system for rapid detection and measurement of glutathione S-transferase placental form (GSTP1) that detoxify polycyclic aromatic hydrocarbons using the cultured rat normal liver epithelial cell line, (RL34) cells. Survey of fruit extracts for GST inducing ability identified both papaya and avocado as significant sources. Benzyl isothiocyanate (BITC) was isolated from papaya methanol extract as a principal inducer of GST activity. Further, the GST inducing ability of a total of 20 isothiocyanates (ITCs) and their derivatives was investigated. Some ITCs showed significant induction, and BITC was one of the most potent inducers among all compounds tested in the present study. The modification of isothiocyanate group (–NCS) or introduction of substituent group to the α-carbon modifies GST induction. Moreover, a significant correlation ( P<0.01, r=0.913) between the GST activity enrichment and GSTP1 protein induction by ITCs was observed. We also indicated that phenethyl ITC and nitrophenyl ITC, potently inducing GST activity, but not inactive benzyl isocyanate, are potential inducers of intracellular reactive oxygen intermediates (ROIs). Our system of GSTP1 induction is appropriate for the chemical research such as screening and identification of novel type of inducers as well as the structure-activity relationship studies, providing mechanistic insight into essential structural elements for GSTP1 induction.

A solid-phase synthetic strategy for the preparation of peptide-based affinity labels: synthesis of dynorphin A analogs.

Solid-phase synthetic methodology was developed for the preparation of peptide-based affinity labels. The initial peptides synthesized were dynorphin A (Dyn A) analogs [Phe(p-X)4,D-Pro10]Dyn A(1-11)NH2 containing isothiocyanate (X=-N=C=S) and bromoacetamide (X=-NHCOCH2Br) groups. The peptides were assembled on solid supports using Fmoc-protected amino acids, and the side chain amine to be functionalized, Phe(p-NH2), was protected by the Alloc (allyloxycarbonyl) group. Following removal of the Alloc group by palladium(O), the reactive isothiocyanate and bromoacetamide functionalities were successfully introduced while the peptides were still attached to the resin. Synthesis of these peptides was carried out on polystyrene (PS) and polyethylene glycol-polystyrene (PEG-PS) resins containing the PAL [peptide amide linker, 5-(4-Fmoc-aminomethyl-3,5-dimethoxyphenoxy)valeric acid] linker. Both the rate of Alloc deprotection and the purity of the crude affinity-labeled peptides obtained were found to be dependent on the resin used for peptide assembly.