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PubMed1994

Total synthesis of a frog poison, (+/-)-epibatidine, a potent non-opioid analgesic.

A non-opioid analgesic, epibatidine (1), isolated from Ecuadoran poison frogs was synthesized in the racemic form starting from a readily available compound 2. A partial Curtius rearrangement product 5 of 2 was converted into 12c by way of the ketone 3 and its condensation product with the pyridine moiety 9c, and catalytic hydrogenation of 12c was specifically conducted in hydrochloric acid-containing 2-propanol for the preferential formation of an exo-product 15b. Conversion of the substituent from 15b to 15a in a single operation using the Vilsmeier reagent, followed by deprotection of the p-toluenesulfonyl group with hydrobromic acid completed an eight-step synthesis of (+/-)-1 from 2.

Analgesics↗
PubMed1988

An improved method for 14C-labelling of farnesylacetic acid and its geranyl ester.

Farnesylacetic acid was efficiently labelled with 14C at the 5-position and gefarnate, a potent ulcer inhibitor, was prepared from it in radioactive form for use in metabolic studies. Condensation of [carbonyl-14C]acetyl chloride (5) with t-butyl 2-ethoxymagnesiomalonate (6) followed by acid-catalyzed deprotection and decarboxylation gave ethyl 3-oxo[3-14C]butanoate (8). Alkylation of the keto ester (8) with geranyl bromide (9) afforded the unsaturated keto ester (10), which was hydrolyzed and decarboxylated to give geranyl[2-14C]acetone (11). Grignard reaction of 11 with cyclopropylmagnesium bromide followed by treatment with hydrobromic acid yielded [4-14C]homofarnesyl bromide (13). Cyanation of 13 with potassium cyanide and subsequent hydrolysis gave [5-14C]farnesylacetic acid (1) in 6.1% yield from barium [14C]carbonate (3). Chlorination of 1 followed by esterification with geraniol afforded [5-14C]gefarnate (2) in 88% yield.

Carbon Radioisotopes↗
PubMed1999

Fullerene Derivatives Bearing a Phosphite Ylide, Phosphonate, Phosphine Oxide, and Phosphonic Acid: Synthesis and Reactivities.

Treatment of phosphites (P(OR)(3)) and MeO(2)CCCCO(2)Me with C(60) affords the corresponding fullerene derivatives (1, R = Me; 2, R = Et; 3, R = n-Bu) consisting of a phosphite ylide group and a cyclopropane ring on the fullerene moiety in high yields. NMR data indicate that all phosphite ylides 1-3 exist as mixtures of E and Z isomers. Under similar reaction conditions, the reaction of phosphinite PPh(2)(OMe) and MeO(2)CCCCO(2)Me with C(60) gives ylide 4. Ylides 1-3 readily undergo hydrolysis with HBr to give corresponding phosphonates 5-7 in excellent yields, while ylide 4 reacts with hydrobromic acid to afford phosphine oxide 8. A mechanism is proposed to account for the formation of these phosphonate derivatives. Further treatment of phosphonate derivative 5 with trimethylsilyl iodide followed by water gave phosphonic acid derivative 9 in 83% yield.

Journal Article↗
PubMed2002

Synthesis of 2-[18F]fluoro-L-tyrosine via regiospecific fluoro-de-stannylation.

2-[18F]Fluoro-L-tyrosine is a fluorine labelled amino acid, known to be incorporated into newly synthesised proteins, rendering it a potentially suitable tracer to image protein metabolism in vivo using positron emission tomography. For the electrophilic preparation of 2-[18F]fluoro-L-tyrosine three protected 2-trialkylstannyl tyrosine derivatives have been synthesised for the first time as precursors. While O,N-di-Boc-2-triethylstannyl-L-tyrosine ethylester has proved to be suitable as precursor for radiosynthesis, imidazolidinon-derivatives of 2-triaklylstannyl tyrosine have not because of difficult fast hydrolysis of a phenolic O-methyl protective group. The di-Boc-tin derivative of tyrosine ethylester readily reacted with [18F]F2, which was prepared via the 18O(p,n)18F nuclear reaction. 2-[18F]Fluoro-L-tyrosine was isolated after full deprotection with aqueous hydrobromic acid and HPLC purification with activities of 1.41 +/- 0.32GBq. The isomeric and enantiomeric purity is high (both >99%). The preparation procedure is facile and easy to automate. The chemical yields of this fluoro-de-stannylation reaction as well as of the synthesis of 6-[18F]fluoro-L-dopa, determined with an analogous precursor and non-radioactive fluorine under identical conditions, amounted to 42.7 +/- 1.6% and 60.2 +/- 2.8%, respectively.

Journal Article↗
PubMed1993

Synthesis and evaluation of 4-amino-substituted 7-methoxy (and 7-hydroxy)- 11-methyl (and 5,11-dimethyl)-10H-pyrido [2,3-b] carbazoles and 4-amino- substituted 11-methyl (and 5,11-dimethyl)-10H-pyrido[3',4':4,5] pyrrolo [3,2-g] quinolines, two new series related to antitumor ellipticine derivatives.

2-Acetyl-4-chloro-3-lithiopyridine ethylene glycol ketal (6b) was reacted with 3-formyl-5-methoxy-1-methyl-indole (9) and 3-formyl-1-methyl-1H-pyrrolo [3,2-c] pyridine (12), giving the corresponding expected alcohols. Reduction of these intermediates with triethylsilane trifluoroacetic acid and subsequent cyclodehydration then led to 4-chloro-7-methoxy-10,11-dimethyl-10H-pyrido [2,3-b] carbazole (8a) and the corresponding 7-aza-analog (8b). The synthesis of 4-chloro-11-methyl (and 5,11-dimethyl)-10-unsubstituted derivatives of these two series was performed through an independent pathway, involving condensation of conveniently substituted 2-amino carbazoles (17) and 7-amino-5H-pyrido [4,3-b] indoles (18) with 5-(ethoxymethylene)-2,2-dimethyl-1,3-dioxane-4,6-dione, thermal cyclization of the resulting compounds with concomitant decarboxylation to the corresponding tetracyclic fused-4-quinolone systems and final chlorination with phosphorus oxychloride. Nucleophilic substitution of various 4-chloro derivatives was then easily performed in an excess of the required dialkylamino alkylamines at reflux and 4-amino substituted-7-hydroxy-10H- pyrido [2,3-b] carbazoles (25d-e) were obtained from 7-methoxy precursors (25a-b), by demethylation with boron tribromide in methylene chloride at -65 degrees C or with boiling 47% hydrobromic acid. Cytotoxicity determination of all new aminosubstituted derivatives and in vivo antitumor evaluation of the most active compounds clearly show that these two series of ellipticine analogs closely related to highly active products are devoid of antitumor properties in two experimental models shown to be sensitive to ellipticines. The place of the pyridinic nitrogen atom in these series has thus been demonstrated to play a crucial role in antitumor activity.

Animals↗
PubMed1975

Facile preparation of 6-chloro-9-amino-2-hydroxyacridine, a urinary metabolite of quinacrine and quinacrine mustard.

6-Chloro-9-amino-2-hydroxyacridine was found to be a metabolite of both quinacrine and the antimalarial alkylating agent quinacrine mustard. Its structure was confirmed by a one-step reaction of quinacrine with 48 percent hydrobromic acid. The presence of this compound as a metabolite of quinacrine mustard suggests a possible in vivo activation mechanism for its antitumor activity and a pharmacological basis for its toxicity to the liver. In vitro experiments showed that this new compound does react with chromosomes and, therefore, can be both a useful chromosome stain and an intercalating agent.

Acridines↗
PubMed1996

Selective determination of volatile N-nitrosamines by derivatization with diethyl chlorothiophosphate and gas chromatography with flame photometric detection.

A selective and sensitive method was developed for the determination of volatile N-nitrosamines by gas chromatography (GC). After denitrosation of N-nitrosamines with hydrobromic acid, the resulting secondary amines were converted into their N-diethylthiophosphoryl derivatives and then measured by GC using a DB-1701 capillary column with flame photometric detection. The calibration graphs for N-nitrosamines in the range 0.05-1 nmol were linear and sufficiently reproducible for quantitative determination. This method was successfully applied to cigarette smoke samples without prior clean-up. N-Nitrosamines and secondary amines were completely separated by extraction with diethyl ether containing 25% 2-propanol. Overall recoveries of N-nitrosamines added to cigarette smoke samples were 83-110%. By using this method, N-nitrosamines in these samples could be determined without any interference from coexisting substances. Analytical results for the contents of N-nitrosamines and secondary amines in mainstream and sidestream smokes of several cigarettes are presented.

Amines↗
PubMed2005

Towards a label-free optical porous silicon DNA sensor.

We report on the fabrication of an optical silicon-based label-free DNA sensor. n-Type crystalline silicon wafers have been electrochemically etched to form porous silicon layers and characterized in terms of porosity, pore distribution, surface composition and photoluminescence. Samples (0.25 cm(2)) have been cut and properly derivatized using trimethoxy-3-bromoacetamidopropylsilane in order to link single strand DNA (ss-DNA). Such a molecule is not commercially available and has been ad-hoc prepared by reacting hydrobromic acid and 3-aminopropyltrimethoxysilane in presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide as coupling agent. Trimethoxy-3-bromoacetamidopropylsilane acts as a bridge anchored to the porous silicon surface through the silane group while immobilizing ss-DNA by means of the bromoacetamido moiety. We have found that derivatized samples exhibit a photoluminescence that is stable in time and is not modified after exposure to non-complementary DNA strand. On the other hand, a sensible enhancement of the light emission has been observed when the derivatized samples react with the complementary strand, showing that the specific ss-DNA/complementary DNA (c-DNA) interaction can be optically sensed without using further labeling steps. This strongly strengthens the possible role of silicon as a material for biosensors.

Biosensing Techniques↗
PubMed2005

Solid phase extraction and determination of sub-ppb levels of hazardous Hg2+ ions.

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions from aqueous samples for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CV-AAS). The Hg(2+) ions were adsorbed selectively and quantitatively during the passage of aqueous samples through octadecyl silica membrane disks modified by isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE). The retained Hg(2+) ions were then stripped from the disk with minimal amounts of 0.5 M hydrobromic acid (two 8 ml portions) as eluent, and determined by CV-AAS. The break-through volume of the method is greater than 3000 ml, which results in enrichment factors >150. Maximum capacity of the membrane disks modified with 10mg of the ligand was found to be 350+/-30 microg of mercury(II), and the limit of detection is 0.005 ng ml(-1). The effect of various cationic interferences on the recovery of mercury in binary mixtures was studied. The method was applied to the recovery of Hg(2+) ions from different synthetic and tap water samples, as well as the determination of mercury in human hair samples.

Environmental Monitoring↗
PubMed2002

Low-temperature, high yield synthesis, and convenient isolation of the high-electron-density cluster compound Ta6Br14.8H2O for use in biomacromolecular crystallographic phase determination.

Reduction of TaBr(5) with Ga in the presence of KBr in a sealed borosilicate ampule at 400 degrees, followed by aqueous Soxhlet extraction and addition of stannous bromide and hydrobromic acid to the extract, yielded Ta(6)Br(14).8H(2)O in 80-84% yield. The new procedure provides a convenient, low temperature, high yield route to the synthesis of the title compound from inexpensive precursors.

Crystallography, X-Ray↗
PubMed2003

Bioreactors for removing methyl bromide following contained fumigations.

Use of methyl bromide (MeBr) as a quarantine, commodity, or structural fumigant is under scrutiny because its release to the atmosphere contributes to the depletion of stratospheric ozone. A closed-system bioreactor consisting of 0.5 L of a growing culture of a previously described bacterium, strain IMB-1, removed MeBr (> 110 micromol L(-1)) from recirculating air. Strain IMB-1 grew slowly to high cell densities in the bioreactor using MeBr as its sole carbon and energy source. Bacterial oxidation of MeBr produced CO2 and hydrobromic acid (HBr), which required continuous neutralization with NaOH for the system to operate effectively. Strain IMB-1 was capable of sustained oxidation of large amounts of MeBr (170 mmol in 46 d). In an open-system bioreactor (10-L fermenter), strain IMB-1 oxidized a continuous supply of MeBr (220 /micromol L(-1) in air). Growth was continuous, and 0.5 mol of MeBr was removed from the air supply in 14 d. The specific rate of MeBr oxidation was 7 x 10(-16) mol cell(-1) h(-1). Bioreactors such as these can therefore be used to remove large quantities of contaminant MeBr, which opens the possibility of biodegradation as a practical means for its disposal.

Air Pollution↗
PubMed1998

Analytical and Sensory Characterization of gamma- and delta-Thiolactones.

gamma-Thiolactones [5-alkyldihydro-2(3H)-thiophenones] and delta-thiolactones (6-alkyltetrahydro-2H-thiopyran-2-ones) were synthesized via isothiouronium salts by reaction of the corresponding oxygen-containing lactones with thiourea and hydrobromic acid. The identity of the compounds was confirmed by means of IR, MS, and (1)H and (13)C NMR. Separation of the enantiomers of the thiolactones was achieved by capillary GC using heptakis(2,3-di-O-methyl-6-O-TBDMS)-beta-cyclodextrin as stationary phase. The substitution of oxygen by sulfur induces tropical fruit notes, which are more pronounced for the delta-thiolactones. Odor thresholds are dependent on ring size and chain length.

Journal Article↗
PubMed1985

New antihistaminic N-heterocyclic 4-piperidinamines. 1. Synthesis and antihistaminic activity of N-(4-piperidinyl)-1H-benzimidazol-2-amines.

The synthesis of a series N-(4-piperidinyl)-1H-benzimidazol-2-amines and the preliminary evaluation of their in vitro and in vivo antihistaminic activity are described. Cyclodesulfurization of (2-aminophenyl)thioureas with mercury(II) oxide resulted in 2-aminobenzimidazole intermediates, which were monoalkylated on the endo-nitrogen atom. After deprotection of the piperidine nitrogen atom with 48% aqueous hydrobromic acid solution, the title compounds were obtained by three different methods, viz. alkylation, reductive amination, or oxirane ring-opening reactions. The in vivo antihistaminic activity was evaluated by the compound 48/80 induced lethality test in rats and histamine-induced lethality test in guinea pigs after oral and/or subcutaneous administration. The duration of action, for a selected number of compounds, was studied in the guinea pig. The phenylethyl derivatives showed the most potent antihistamine properties after oral administration in both animal species.

Administration, Oral↗
PubMed1990

Synthesis and antitumor activity of 1-[[(dialkylamino)alkyl]amino]-4-methyl-5H-pyrido[4,3-b]benzo[e]- and -benzo[g])indoles. A new class of antineoplastic agents.

The thermal Fischer indolization of hydrazones resulting from 4-hydrazino-5-methyl-1H-pyridin-2-one and various beta- and alpha-tetralones led to 4-methyl-6,7-dihydro-2H,5H-pyrido[4,3- b]benzo[e]indol-1-ones and 4-methyl-11-dihydro-2H,5H-pyrido[4,3- b]benzo[g]indol-1-ones, respectively. After aromatization, these compounds were transformed by phosphorus oxychloride, giving 1-chloro-4-methyl-5H-pyrido[4,3- b]benzo[e]- and -benzo[g]indoles which were substituted by [(dialkylamino)alkyl]amines. The resulting 1-[[(dialkylamino)alkyl]amino]-4-methyl-5H-pyrido- [4,3-b]benzo[e]- and -benzo[g]indoles, as well as hydroxy derivatives obtained by demethylation of methoxylated compounds with hydrobromic acid, were tested for antitumor activity in vitro (leukemic and solid tumor cells) and in vivo on various experimental tumor models using the standard NCI protocols. 1-[[3-(Dialkylamino)propyl]-amino]-4-methyl-9-hydroxy-5H-pyrido[4,3- b]benzo[e]indoles appeared as a promising new class of antineoplastic agents.

Animals↗
PubMed1988

Synthesis and antitumor activity of analogues of ifosfamide modified in the N-(2-chloroethyl) group.

A series of 3-(2-chloroethyl)-N-(2-X-ethyl)tetrahydro-2H-1,3,2-oxazaphosphorin -2-amine 2-oxides with various X substituents have been prepared by cyclization of racemic ifosfamide or its enantiomers with sodium hydride and subsequent treatment of intermediary products with hydrobromic acid, diethyl hydrogen phosphate, dibenzyl hydrogen phosphate, p-toluenesulfonic acid, and acetic acid. All of these compounds were tested in vivo against L 1210 lymphoid leukemia in mice. Only bromo analogue 13 and its enantiomers were effective, exceeding the activity of racemic ifosfamide and cyclophosphamide. The therapeutic index of the racemic 13 and its levorotatory enantiomer was about 1.7 times higher than that for ifosfamide and about 2.7 times higher than that for cyclophosphamide.

Animals↗
PubMed2002

Preparation of 7-alkylamino-2-methylquinoline-5,8-diones.

Several novel 7-alkylamino-2-methylquinoline-5,8-diones (2) were synthesized from 2,5-dimethoxyaniline in five steps via the Skraup reaction followed by demethylations, oxidative bromination, amination, and debromination. We have achieved an unusual hydrobromic acid catalyzed debromination reactions of several 6-bromo-7-alkylamino-2-methylquinoline-5,8-diones, giving 7-alkylamino-2-methylquinoline-5,8-diones in good yields.

Journal Article↗
PubMed2004

Antineoplastic agents 491. Synthetic conversion of aaptamine to isoaaptamine, 9-demethylaaptamine, and 4-methylaaptamine.

Aaptamine (1) was used as starting material for synthetic transformation to isoaaptamine (2), 9-demethylaaptamine (5), and 4-methylaaptamine (6). A general method for the selective O-demethylation of such 1H-benzo[de][1,6]-naphthyridine (1) marine sponge constituents at position C-9 has been developed. Selective O-demethylation of aaptamine (1) and 1-methylaaptamine (11) with 48% hydrobromic acid led to 9-demethylaaptamine (5) and isoaaptamine (2), respectively. A selection of other aaptamine derivatives were synthesized, and their structures were unambiguously determined by X-ray methods. In addition, their cancer cell growth inhibitory properties were evaluated against the murine P388 lymphocytic cell line and a minipanel of human cancer cell lines. Evaluation as inhibitors of the PKC signal transduction pathway and against a selection of microorganisms was also undertaken. Aaptamine derivatives 3 and 5 had broad-spectrum antimicrobial activities.

Animals↗
PubMed2005

Metal-mediated entry to functionalized 3-substituted 3-hydroxyindolin-2-ones via regiocontrolled carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions of isatins in aqueous media.

Reactions of 2,3-indolinediones (isatins) with stabilized organometallic reagents were investigated in aqueous media. Isatins and a variety of stabilized organic halides undergo coupling under Barbier-type conditions in the presence of different metals (indium, tin, zinc) and additives (ammonium chloride, hydrobromic acid, bismuth(III) chloride, hafnium(IV) chloride). The regiochemistry of the processes (carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions) were generally excellent. On this basis, simple and fast protocols for the synthesis of the potentially bioactive 3-substituted 3-hydroxyoxindole moiety were developed.

Allyl Compounds↗