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At least 163 records · Page 9Linked to original sources
PubMed1997

2-Carbomethoxy-3-aryl-8-oxabicyclo[3.2.1]octanes: potent non-nitrogen inhibitors of monoamine transporters.

Cocaine is a potent stimulant of the mammalian central nervous system. Its reinforcing and stimulant properties have been associated with its propensity to bind to monoamine transporter systems. It has generally been assumed that the amino function on monoamines is a requirement for binding to monoamine transporters. In particular, the 8-amino function on the tropane skeleton of cocaine and cocaine analogs has been assumed to provide an ionic bond to the aspartic acid residue on the dopamine transporter (DAT). We have prepared the first 8-oxa analogs of the 3-aryltropanes (WIN compounds) and have found that the 3 beta-(3,4-dichlorophenyl) (6g) and 3 alpha-(3,4-dichlorophenyl) (7g) analogs are particularly potent (IC50 = 3.27 and 2.34 nM, respectively) inhibitors of the dopamine transporter. We now describe the synthesis and biology of the family of 2-carbomethoxy-3-aryl-8-oxabicyclo[3.2.1]octanes and demonstrate that an amino nitrogen is not required for binding to the DAT.

Animals↗
PubMed2002

Rearrangement of a mesylate tropane intermediate in nucleophilic substitution reactions. Synthesis of aza-bicyclo[3.2.1]octane and aza-bicyclo[3.2.2]nonane ethers, imides, and amines.

Nucleophilic substitution of 2beta-mesyloxymethyl-N-methyl-3beta-p-tolyl-tropane intermediate with alkoxides, metal imides, or amines was found to lead not only to the expected bicyclo[3.2.1]octane (tropane) ether, imide, and amine derivatives but also to unexpected bicyclo[3.2.2]nonane derivatives. When alkoxides were used as nucleophile, only the rearranged bicyclo[3.2.2]nonane structure was obtained, whereas the use of amines or imides as nucleophile afforded a mixture of the two structures. The bicyclo[3.2.2]nonane structure was assigned by NMR analysis.

Alkanes↗
PubMed2003

Intramolecular hydrogen abstraction reaction promoted by N-radicals in carbohydrates. Synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane ring systems.

The reaction of phenyl and benzyl amidophosphates and alkyl and benzyl carbamate derivatives of aminoalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane ring systems under neutral conditions. This reaction can be considered to be an intramolecular N-glycosidation that goes through an intramolecular 1,5-hydrogen abstraction promoted by an N-amido radical followed by oxidation of the transient C-radical intermediate to an oxycarbenium ion. This methodology proved to be useful not only as a suitable strategy for the preparation of these bicyclic arrays but also for the selective oxidation of specific carbons of the carbohydrate skeleton, constituting a good procedure for the synthesis of protected N,O-uloses.

Carbohydrates↗
PubMed2006

Single site electronic spectroscopy of magnesium isobacteriochlorin in n-octane matrixes at 7 K.

The high resolution, single site emission and absorption spectra of magnesium isobacteriochlorin (MgiBC) in n-octane matrixes at 7 K are reported. Its emission and Q and Soret band absorption regions have been investigated. The vibrational frequencies of the ground and the lowest energy pipi* singlet excited states were determined from luminescence and excitation spectra, respectively. The emission from MgiBC at 7 K seems to be entirely fluorescence. The luminescence and Q(y) region spectra of the complex are similar, having intense, narrow origin bands followed by relatively weak, but orderly vibrational structure. The Q(x) region does not have a clear origin and exhibits complex vibrational structure that increases in intensity going to higher energy. In the Soret region the individual pipi* origins are clearly identifiable and some vibrational structure was also observed.

Absorption↗
PubMed2005

Pressure-induced protein unfolding in the ternary system AOT-octane-water is different from that in bulk water.

In a cellular environment, the presence of macromolecular cosolutes and membrane interfaces can influence the folding-unfolding behavior of proteins. Here we report on the pressure stability of alpha-chymotrypsin in the ternary system bis(2-ethylhexyl)sodium sulfosuccinate-octane-water using FTIR spectroscopy. The ternary system forms anionic reverse micelles which mimic cellular conditions. We find that inclusion of a single protein molecule in a reverse micelle does not alter its conformation. When pressurized in bulk water, alpha-chymotrypsin unfolds at 750 MPa into a partially unfolded structure. In contrast, in the ternary system, the same pressure increase induces a random coil-like unfolded state, which collapses into an amorphous aggregate during the decompression phase. It is suggested that the unfolding pathway is different in a cell-mimicking environment due to the combined effect of multiple factors, including confinement. A phase transition of the reverse micellar to the lamellar phase is thought to be essential to provide the conditions required for unfolding and aggregation, though the unfolding is not a direct result of the phase transition. Our observations therefore suggest that membranes may cause the formation of alternative conformations that are more susceptible to aggregation.

Animals↗
PubMed2004

Extraction of zirconium nitrate by TBP in n-octane: influence of cation type on third phase formation according to the "sticky spheres" model.

Small-angle neutron scattering (SANS) data for the tri-n-butyl phosphate (TBP)-n-octane, HNO(3)-Zr(NO(3))(4) solvent extraction system, obtained under a variety of experimental conditions, have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in scattering intensity in the low Q range observed when increasing amounts of Zr(NO(3))(4) were extracted into the organic phase was interpreted as arising from interactions between small reverse micelle-like particles containing two to three TBP molecules. Upon extraction of Zr(NO(3))(4), the particles interact through attractive forces between their polar cores with a potential energy that exceeds 2 k(B)T. The interparticle attraction, under suitable conditions, leads to third phase formation. A linear relationship exists between the derivative of the potential energy of attraction with respect to the concentration of nitrate ions in the organic phase and the ionization potential or the hydration enthalpy of the extracted metal cations.

Cations↗
PubMed1999

Desymmetrization by ring-closing metathesis leading to 6,8-dioxabicyclo[3.2.1]octanes: a new route for the synthesis of (+)-exo- and endo-brevicomin.

[formula: see text] The 6,8-dioxabicyclo[3.2.1]octane skeleton is a common structural subunit in natural products. A conceptionally new strategy affording these structures is described for the syntheses of (+)-exo-brevicomin and rac-endo- and enantiomerically enriched (+)-endo-brevicomin, employing desymmetrization of trienes derived from diols with C2 and meso symmetry via ring-closing metathesis.

Animals↗
PubMedDate not supplied

[The lipase/lipoxygenase bienzyme system in AOT reversed micelles in octane].

In this work it is shown that the bienzyme lipase/lipoxygenase system can function in reversed micelles of bis(2-ethyl)hexyl sulfosuccinate (AOT) in octane. As a lipase substrate, a fish fat preparation (fat of sea mammals) with a high content of polyunsaturated fatty acids was used. It was demonstrated that the bienzyme reaction proceeded in a stationary mode and had a rate-limiting step catalyzed by lipase. Under optimal conditions, the efficacy of functioning of the bienzyme system was by an order of magnitude higher than that in water. The lipase/lipoxygenase bienzyme system can be used as a new method of spectrophotometric determination of lipase activity. The English version of the paper.

Animals↗
PubMed2003

A solid-phase approach towards the development of 3-aza-6,8-dioxabicyclo[3.2.1]octane scaffolds.

The development of new strategies for solid-phase synthesis of 3-aza-6,8-dioxabicyclo[3.2.1]octane scaffolds, named BTKa, is described. The preparation was made possible by the combination of three components: amines, alpha-halo-acetophenones, and sugar or tartaric acid derivatives. By anchoring each of the three components it was possible to synthesize BTKa compounds either as amino alcohols or amido esters. The compatibility of the protocols with different classes of amines and substituted alpha-halo-acetophenones was demonstrated.

Acetophenones↗
PubMed1991

Bioconversion of n-octane to octanoic acid by a recombinant Escherichia coli cultured in a two-liquid phase bioreactor.

The alk genes from the catabolic OCT plasmid of Pseudomonas oleovorans, which encode the enzymes involved in the oxidation of n-alkanes to carboxylic acids, were introduced into E. coli W3110. The resulting recombinant converts n-octane in a two-liquid phase medium into the corresponding alkanoate and excretes this compound into the aqueous phase. The rate of octanoic acid production by the recombinant E. coli is equal to or better than the alkane oxidation rate of P. oleovorans, suggesting that two-liquid phase fermentations with E. coli might have future industrial applications.

Caprylates↗
PubMed1997

Formation of homo- and heterooligomeric supramolecular structures by D-glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase in reversed micelles of aerosol OT in octane.

The supramolecular structure of oligomeric enzymes can be specifically regulated by changing the size of an inner cavity of Aerosol OT reversed micelles in octane. Both D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and lactate dehydrogenase (LDH) reveal an ability to exist and function in monomeric, dimeric and tetrameric forms (homooligomers). Various heterooligomeric complexes, in particular, GAPDH monomer--LDH monomer, GAPDH dimer--LDH tetramer were detected in reversed micelles.

Animals↗
PubMed1999

Sedimentation analysis of muscle glycogen phosphorylase b entrapped in hydrated reversed micelles of aerosol OT in octane.

The oligomeric state and formation of supramolecular structures of glycogen phosphorylase b from rabbit skeletal muscles have been studied in the system of hydrated reversed micelles of aerosol OT (AOT) in octane. Sedimentation studies show that the oligomeric state of the enzyme is controlled by the degree of hydration of micelles. Monomeric, dimeric, trimeric, tetrameric, hexameric, or octameric forms of the enzyme were observed depending on the degree of micelle hydration.

Animals↗
PubMed1999

General collection efficiency in liquid iso-octane and tetramethylsilane used as sensitive media in a thimble ionization chamber.

The general collection efficiency in the dielectric liquids iso-octane (CaH18; 2-2-4 trimethylpentane) and tetramethylsilane (Si(CH3)4), used as sensitive media in a thimble liquid ionization chamber (LIC) with a liquid layer thickness of 1 mm, has been studied. Measurements were made for continuous radiation at varying dose rates using 140 keV photons from the decay of 99mTc for chamber polarizing voltages of 50, 100 and 500 V. The maximum dose rate in each measurement session was about 150 mGy min(-1). The experimental results were compared with theoretical general collection efficiencies calculated by the equation for the general collection efficiency in gases. The results show that the general collection efficiency in a thimble LIC for continuous radiation can be calculated with the equation for the general collection efficiency in gas ionization chambers, using the same chamber geometry correction factors and analogous characteristic ion recombination parameters for the dielectric liquids.

Equipment Design↗
PubMed2003

(Z)-2-(3-hydroxy-4-methoxybenzylidene)-1-azabicyclo[2.2.2]octan-3-one.

Crystals of the title compound, C(15)H(17)NO(3), were obtained from a condensation reaction of 3-hydroxy-4-methoxybenzaldehyde with 1-azabicyclo[2.2.2]octan-3-one and subsequent crystallization of the product from methanol. The title compound, containing a double bond that connects the azabicyclic ring system to the 3-hydroxy-4-methoxybenzylidene group, was obtained with Z geometry.

Crystallography, X-Ray↗
PubMed2003

Synthetic study of optically active 3-azabicyclo[3.3.0]octane-2,6,8-tricarboxylic acid.

Synthesis of (1R,2S,5S,6R,8S)-3-azabicyclo[3.3.0]octane-2,6,8-tricarboxylic acid (2) from trans-4-hydroxy-L-proline (5) was attempted. A Diels-Alder reaction of 3,4-dehydroproline derivative 9 and cyclopentadiene afforded a single stereoisomer 11. The Diels-Alder adduct was smoothly converted to the hydrochloride of 2 (24) via RuO(4) oxidation. Although some racemization of the material or product was observed during the synthetic processes, the amino acid 24 proved to be optically pure.

Octanes↗