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PubMed2002

Intramolecular Diels-Alder reactions of brominated masked o-benzoquinones. A detour method to synthesize highly functionalized oxatricyclic [m.3.1.0] ring systems from 2-methoxyphenols.

Intramolecular Diels-Alder (IMDA) reactions of masked o-benzoquinones (MOBs) 5a-d to 7a-d and 17a-d to 19a-d generated in situ from 2-methoxyphenols 2-4 and 14-16, respectively, in the presence of alkenols 1a-d, resulting in highly functionalized oxatricyclic [m.3.1.0] ring systems are described. The MOBs 5a-d to 7a-d underwent the IMDA reactions to furnish the adducts 8a-d, 10a-d, and 12a-d (direct method) in poor yields with the concomitant formation of considerable amounts of unexpected byproducts 9a-d, 11a-d, and 13a-d, respectively. To avoid the formation of byproducts and to improve the yields of the desired cycloadducts, a detour method comprising sequential bromination of 2-methoxyphenols 2-4, tandem oxidative acetalization-Diels-Alder reaction, and debromination has been developed. The oxidation of bromophenols 14-16 in the presence of alkenols 1a-d produced the corresponding MOBs 17a-d to 19a-d, which underwent cycloaddition to afford the cycloadducts 20a-d to 22a-d, respectively, as sole products in good to high yields in a highly regio- and stereoselective manner. Treatment of the bromoadducts 20a-d to 22a-d with tributylammonium formate-palladium reagent produced the corresponding debrominated products 8a-d, 10a-d, and 12a-d in high to excellent yields. In general, the latter oxatricycles were obtained in higher overall yields via the detour method than those via the direct method.

Alkaloids↗
PubMed2001

2-Azabicyclo[2.1.1]hexanes. 2. Substitutent effects on the bromine-mediated rearrangement of 2-azabicyclo[2.2.0]hex-5-enes.

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 have been prepared by photoirradiation of appropriately substituted 1,2-dihydropyridines. Torquoselectivity is observed in the synthesis of the 3-endo-methyl- and 3-endo-phenyl-2-azabicyclo[2.2.0]hexenes 6c-e from 2-methyl- and 2-phenyl-1,2-dihydropyridines 5c-e. Products formed upon addition of bromine to 3-endo-, 4-, and 5-methyl- and 3-endo-phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6a-f were substituent dependent. For 6a,b, which lack substituents at C(3) or C(5), mixtures of unrearranged dibromides 8a,b and rearranged dibromides 9a,b were obtained. With the 3-endo-substituents in 6c-e, only rearranged dibromides 9c-e were formed; 5-methyl substitution afforded mainly unrearranged dibromide 8f and some allylic bromide 10. Both unrearranged 5-endo,6-exo-dibromo-2-azabicyclo[2.2.0]hexanes 8 and rearranged 5-anti-6-anti-dibromo-2-azabicyclo[2.1.1]hexanes 9 are formed stereoselectively. The dibromoazabicyclo[2.1.1]hexanes 9 have been reductively debrominated to afford the first reported 2-azabicyclo[2.1.1]hexanes 11 with alkyl or aryl substituents at C-3.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed2000

Synthesis of 4-substituted phenyl 2,5-anhydro-1,6-dithio-alpha-D-gluco- and -alpha-L-guloseptanosides possessing antithrombotic activity.

Two independent approaches were investigated for the synthesis of 3,4-di-O-acetyl-1,6:2,5-dianhydro-1-thio-D-glucitol (18), a key intermediate in the synthesis of 1,3,4-tri-O-acetyl-2,5-anhydro-6-thio-alpha-D-glucoseptanose (13), needed as glycosyl donor. In the first approach 1,6-dibromo-1,6-dideoxy-D-mannitol was used as starting material and was converted via 2,5-anhydro-1,6-dibromo-1,6-dideoxy-4-O-methanesulfonyl-3-O-tetrahydropy ranyl-D-glucitol into 18. The second approach started from 1,2:5,6-di-O-isopropylidene-D-mannitol and the allyl, 4-methoxybenzyl as well as the methoxyethoxymethyl groups were used, respectively, for the protection of the 3,4-OH groups. The resulting intermediates were converted via their 1,2:5,6-dianhydro derivatives into the corresponding 3,4-O-protected 2,5-anhydro-6-bromo-6-deoxy-D-glucitol derivatives. The 1,6-thioanhydro bridge was introduced into these compounds by exchanging the bromine with thioacetate, activating OH-1 by mesylation and treating these esters with sodium methoxide. Among these approaches, the 4-methoxybenzyl protection proved to be the most suitable for a large scale preparation of 18. Pummerer rearrangement of the sulfoxide, obtained via oxidation of 18 gave a 1:9 mixture of 1,3,4-tri-O-acetyl-2,5-anhydro-6-thio-alpha-L-gulo- (12) and -D-glucoseptanose 13. When 12 or 13 were used as donors and trimethylsilyl triflate as promoter for the glycosylation of 4-cyanobenzenethiol, a mixture of 4-cyanophenyl 3,4-di-O-acetyl-2,5-anhydro-1,6-dithio-alpha-L-gulo- (58) and -alpha-D-glucoseptanoside (61) was formed suggesting an isomerisation of the heteroallylic system of the intermediate. A similar mixture of 58 and 61 resulted when 18 was treated with N-chloro succinimide and the mixture of chlorides was used in the presence of zinc oxide for the condensation with 4-cyanobenzenethiol. When 4-nitrobenzenethiol was applied as aglycon and boron trifluoride etherate as promoter, a mixture of 4-nitrophenyl 3,4-di-O-acetyl-2,5-anhydro-1,6-dithio-alpha-L-gulo- (60) and -alpha-D-glucoseptanoside (62) was obtained. Deacetylation of 58, 61 and 62 according to Zemplen afforded 4-cyanophenyl 2,5-anhydro-1,6-dithio-alpha-L-glucoseptanoside (59), 4-cyanophenyl 2,5-anhydro-1,6-dithio-alpha-D-glucoseptanoside (63) and 4-nitrophenyl 2,5-anhydro-1,6-dithio-alpha-D-glucoseptanoside (66), respectively. The 4-cyano group of 63 was transformed into the 4-aminothiocarbonyl, and the 4-(methylthio)(imino)methyl derivative and the 4-nitro group of 66 into the acetamido derivative. All of these thioglycosides displayed a stronger oral antithrombotic effect in rats compared with beciparcil, used as reference.

Administration, Oral↗
PubMed1998

Prospecting for potentially new pharmaceuticals from natural sources.

Many new natural product-derived pharmaceutically active compounds and compositions, each effective in treating an array of diseases and maladies including various tumors and HIV, have been reportedly isolated from different sources of vegetation, including the bark of yew trees, needles, leaves, fungi, and cell culture of many different species; vegetables such as West African yams; and Chinese and Indian herbs. Other sources include vegetation from South American rainforests. Many of the sources of such natural products are historical in nature and/or are known from folklore. Recent studies have provided potentially new biodiverse pharmaceutical compounds such as paclitaxel, which is obtainable from several species, including various portions of T. brevifolia, the Western yew tree, and other yew species such as T. baccata, T. cuspidata, T. wallichiana, T. media, T. canadensis, T. chinensis and T. yunnanensis as well as from T. wardii, T. capitata, T. brownii, T. gem, T. globosa, T. floridana, T. hicksii, T. densiformis, and T. darkgreen spreader, in addition to cultured plant cells and fungi. The novel compounds and their semisynthetic brominated and chlorinated analogs prepared from T. yunnanensis extract show strong activity against several types of tumors.

Animals↗
PubMed2005

Incompatibility of metam sodium with halogenated fumigants.

Metam sodium (metam) is a widely used soil fumigant. Combined application of metam and other available fumigants is intended to produce synergic pesticidal effects for a broad spectrum of pest control in soil fumigation. This study aimed to test the compatibility of metam with the halogenated fumigants 1,3-dichloropropene (1,3-D), chloropicrin, methyl bromide, methyl iodide and propargyl bromide. Halogenated fumigants and metam were spiked simultaneously into organic solvents, water and moist soils, and metam-induced degradation of these halogenated chemicals was evaluated. In all three media, the halogenated fumigants were incompatible with metam and degraded via rapid chemical reactions. The degradation rate varied with halogenated fumigant species and increased as the amount of metam present was increased. In moist soil, 15-95% of the halogenated fumigants were decomposed within 72 h by metam at a 1:1 molar ratio. Combined application of Telone C-35 (62.5% 1,3-D + 35% chloropicrin) at 265 mg kg(-1) and Vapam (42% metam) at 567 mg kg(-1) in soil resulted in complete disappearance of the applied chloropicrin and 20-38% of the 1,3-D within 8 h. The results suggest that simultaneous application of halogenated fumigants and metam at the same soil depth will not maximize pest control. In practice, sequential treatment of soil or application at different soil depths is recommended when these two types of fumigants are used in combination.

Allyl Compounds↗
PubMed1999

Spatial distribution of extractable organohalogens in northern pink shrimp in the north Atlantic.

Extractable organohalogens (EOX) are organic compounds that contain chlorine, bromine and/or iodine, which can be separated from the matrix by liquid/liquid or liquid/solid extraction. A combination of instrumental neutron activation analysis (INAA) and solvent extraction methods has been developed for the determination of EOX from the shrimp Pandalus borealis. Levels of EOX were evaluated for spatial trends for shrimp caught in several areas off the Labrador coast, off the coast of Nova Scotia, and off the coast of Maine. Muscle contained 1.09-6.05 micrograms EOCl/g tissue and 105-498 micrograms extractable organochlorine (EOCl)/g lipid; 0.0607-0.288 microgram extractable organobromine (EOB)r/g tissue and 4.74-10.5 micrograms EOBr/g lipid; and 0.014-0.048 microgram extractable organoiodine (EOI)/g tissue and 1.03-1.76 micrograms EOI/g lipid, respectively. The levels of EOCl in roe were 1.60-12.34 micrograms/g tissue and 39.0-146 micrograms/g lipid. In roe, the EOBr levels were 0.707-1.03 micrograms/g tissue and 6.96-13.5 micrograms/g lipid; and EOI levels were 0.123-0.349 microgram/g tissue and 1.42-4.11 micrograms/g lipid. The EOCl, EOBr, and EOI levels in roe increased noticeably from north to south along the coast of Labrador. Samples taken from the coast of Maine and from Canso Hole were typically higher in EOCl levels than those taken from Labrador. The results for EOBr and EOI were in the same range as those from Labrador.

Animals↗
PubMed1994

1,N2-cyclic deoxyguanosine adducts and guanine adducts of 2-haloacroleins. Isolation, characterization, isomerization and stability.

The reaction of the mutagenic 2-haloacroleins, 2-fluoroacrolein, -2-chloroacrolein and 2-bromoacrolein, with nucleosides and 5'-mononucleotides was studied. We found two different regioisomers of 1,N2-cyclic deoxyguanosine adducts of 2-chloroacrolein and 2-bromoacrolein: type A, the 6-hydroxy, 7-haloadduct in which the OH-substituent is vicinal to the N2-atom of the guanine moiety and type B, the 8-hydroxy, 7-haloadduct in which the OH-group is adjacent to the N1-atom of the guanine moiety. The major adducts were the trans pairs of diastereomers of type A and type B in which the 6,7-substituents as well as the 7,8-substituents are in the energetically favoured diaxial position of the newly formed tetrahydropyrimidine ring. In the case of the type A regioisomers, the cis pairs of diastereomers (traces with chloroacrolein and about 4% with bromoacrolein) were also found in which the halosubstituent probably takes the equatorial position. Due to the anomeric effect, the OH-group takes the axial position in both regioisomers. No cis isomers of the type B regioisomers could be isolated. Acid hydrolysis of the deoxyguanosine adducts released deoxyribose, and the respective guanine adducts were isolated and characterized. Besides the vicinal halo, hydroxy adducts, trace amounts of the corresponding dihydroxy adducts were formed by hydrolysis of the chlorine or bromine substituents. The dihydroxy compounds possess the same structures and conformations in the newly formed tetrahydropyrimidine ring as do the halo, hydroxy adducts. Under our conditions no adducts other than those with deoxyguanosine and guanine could be identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrolein↗
PubMed2006

Ab initio and DFT study on the electrophilic addition reaction of bromine to tetracyclo[5.3.0.0(2,6).0 (3,10)]deca-4,8-diene.

The electronic and geometric structures of tetracyclo[5.3.0.0(2,6).0(3,10)]deca-4,8-diene (hypostrophene) have been investigated by ab initio and DFT/B3LYP methods using the 6-31G* and 6-311G* basis sets. The double bonds of hypostrophene are endo-pyramidalized. The cationic intermediates and products formed in the addition reaction have been investigated using the HF/6-311G*, HF/6-311G**, and B3LYP/6-311G* methods. The bridged bromonium cation was more stable than the U-type cation. Considering that the bridged cation does not isomerize to the less stable U-type cation, it is not possible for the U-type product to be obtained in the reaction. The bridged bromonium cation transformed into the more stable N-type cation and the N-type product was obtained via this cation. The thermodynamic stability of the exo, exo and exo, endo isomers of the N-type dibromide molecule were almost identical. The N-type product was 16.6 kcal mol(-1) more stable than the U-type product.

Bromine↗
PubMed1983

omega-haloalkyl esters of 5'-adenosine monophosphate as potential active-site-directed reagents for dehydrogenases.

A series of esters of adenosine 5'-monophosphate with ethyl, propyl, or hexyl moieties substituted at the omega-position with chlorine or bromine were prepared. The compounds were competitive inhibitors of horse liver alcohol dehydrogenase with respect to coenzyme, NAD+, and had inhibition (dissociation) constants in the range of 40 to 260 microM at pH 8.0, 25 degrees C. The bromoalkyl esters were designed to be active-site-directed inactivators and were chemically reactive as tested with the model compound 4-(p-nitrobenzyl)pyridine. Yeast alcohol dehydrogenase was inactivated by the bromohexyl analog by an active-site-directed mechanism, with a Ki = 1.5 mM and a pseudo-bimolecular rate constant of 0.03 M-1 S-1, which is 150 times larger than the bimolecular rate constant for inactivation by 2-bromoethanol. However, the rates of inactivation of other dehydrogenases treated with 10 mM concentrations of these compounds were generally slower than with the simpler reagent, 2-bromoethanol. Thus, the reactive functional group attached to the AMP moiety may not be properly oriented for affinity labeling of these dehydrogenases. The bromoalkyl esters may be useful for inactivating other enzymes.

Adenosine Monophosphate↗
PubMed1993

Formation of alpha-(1-->6), alpha-(1-->3), and alpha-(1-->2) glycosidic linkages by dextransucrase from Streptococcus sanguis in acceptor-dependent reactions.

Dextransucrase from Streptococcus sanguis 10558 was found to synthesize alpha-(1-->6), alpha-(1-->3), and alpha-(1-->2) linkages during an acceptor-dependent glucosyl transfer reaction. Normally, new glucosyl residues are added at C-6 of monosaccharide acceptors. However, sugars blocked at C-6 also can serve as good acceptors. The disaccharide and trisaccharide products formed when methyl 6-bromo-6-deoxy-alpha-D-glucopyranoside was used as acceptor were isolated and characterized. Both were found to contain only alpha-(1-->3) glycosidic bonds. This supports the hypothesis that when C-6 is blocked the acceptor binds to the enzyme in a flipped orientation, resulting in an approximate exchange in space of the C-3 and C-6, thereby putting C-3 adjacent to the active site. The second alpha-(1-->3) links in the trisaccharide are formed by a single-chain mechanism without release of the intermediate disaccharide. With maltose as acceptor, new glucosyl residues are added at C-6'. However, if that position is blocked with a bromine atom, the resulting compound, 6'-bromo-6'-deoxy-maltose, can still serve as an acceptor. The product in this case was isolated and characterized. The new glycosidic link was found to be alpha-(1-->2).

Carbohydrate Conformation↗
PubMed1986

Selective mutagenic activity of 2-bromo-propanamides on Salmonella typhimurium. A structure-activity study.

Nineteen 2-halogeno-acetamides, -propanamides, and -iso-butyramides and four related epoxyamides were tested as mutagens for Salmonella typhimurium TA100. Mutagenic activity was observed in strictly selected 2-halogenoamides and in all epoxyamides. The effectiveness of 2-halogenoamides depends upon: the character of the carbon carrying the halogen (1 degree, 2 degrees, 3 degrees); the nature of the halogen (Br, Cl); the substitution at nitrogen. Some considerations concerning the selectivity observed are presented.

Alkylating Agents↗
PubMed1994

Insecticidal and cytotoxic effects of natural and hemisynthetic destruxins.

The insecticidal and cytotoxic effects of 13 natural and hemisynthetic destruxins have been studied. DE shows insecticidal effects similar to those of DA, while DE and DA are more active than all the other natural compounds and analogues tested. Brominated destruxin is a relatively active analogue displaying particular modalities of cytotoxic effects which reflect a certain originality of its mode of action. The linear molecule resulting from the opening of the DA cycle is not toxic. The most hydrophilic destruxins showing e.g. charged radicals (COO-) appear the least toxic probably because they do not penetrate easily the cellular membranes.

Administration, Oral↗
PubMed2002

Brominated metabolites from an Okinawan Laurencia intricata.

Two halogenated C(15) acetogenins, itomanallenes A and B, with a terminal bromoallene moiety along with a halogenated sesquiterpene, itomanol, have been isolated from the red alga Laurencia intricata collected in Okinawan waters. Their structures were deduced from 1D and 2D NMR experiments including (1)H-(1)H COSY, HSQC, HMBC, and NOESY methods. The alcohol corresponding to itomanallene B seems to be a plausible precursor of itomanallene A, which has an unusual 2,10-dioxabicyclo[7.3.0]dodecene skeleton. Itomanol was found to be a selinane-type bromosesquiterpenoid, and is the first example of a selinane to be isolated from Japanese Laurencia species.

Bromine↗
PubMed2002

AM1 CI and ZINDO/S study of quaternary salts of diazaphenanthrenes with haloalkanes.

For quaternary salts of diazaphenanthrenes 1-3 with methyl iodide 4-6, diiodomethane 7-9 and 1,2-dibromoethane 10-12 UV spectral values have been calculated by AM1 CI, and in the case of 4-6 also with ZINDO/S method. Correlations of experimental and calculated wavenumber values of considered compounds show good compatibility. For geometry optimisation of 4-9 the AM1 CI method has been used.

Alkanes↗
PubMed2004

Development of a solid-phase microextraction gas chromatography/tandem mass spectrometry method for polybrominated diphenyl ethers and polybrominated biphenyls in water samples.

Solid-phase microextraction has been applied for the first time to the determination of trace concentrations of some brominated flame-retardant compounds (BFRs) in water samples. For the development of the method, six polybrominated diphenyl ethers and two polybrominated biphenyls were considered as target analytes. The factors expected to influence the extraction process are fully discussed. Quantification has been performed by gas chromatography/tandem mass spectrometry using an ion trap mass analyzer. This is also the first time that tandem mass spectrometry is applied with these analytes. Unlike conventional methods for BFR analysis, which involve solvent extraction and several cleanup steps before gas chromatography, the proposed method uses headspace extraction and hard contamination of the chromatographic system is prevented. In addition, tandem mass spectrometry provides selectivity and sensitivity in the detection process. The method performs well achieving good linearity (R(2) > 0.997), precision, and detection limits (S/N = 3) ranging from 7.5 to 190 pg/L. The method has been applied to a variety of water samples.

Journal Article↗
PubMed2000

Development of an immunochemical technique for the analysis of trichlorophenols using theoretical models.

An immunoassay has been developed for trichlorophenol analysis on the basis of theoretical chemistry modeling studies. These data have allowed us to choose the optimum chemical structure of the immunizing hapten according to realistic similarities with the target analyte. The synthesis of this hapten and the subsequent application of an appropriate immunization protocol have lead to the production of polyclonal antibodies against the target analyte. A homologous direct competitive ELISA has been developed that can be carried out in about 1 h. It has a limit of detection of 0.2 +/- 0.06 microg/L (1.01 +/- 0.3 nM) and it has been proven to tolerate a wide range of ionic strengths and pH values. Thus, the assay has acceptable features in samples with ionic strength between 4 and 56 mS/cm and pH values between 5.5 and 9.5. Studies on the selectivity of this immunoassay have demonstrated a high recognition of the corresponding brominated analogues. Other phenolic compounds do not interfere significantly in the analysis of 2,4,6-trichorophenol using this immunochemical technique. The accuracy of the assay has been evaluated using certified and spiked samples.

Animals↗