A Ring Contraction Strategy toward a Diastereoselective Total Synthesis of (+)-Bakkenolide A

A diastereoselective route to (+)-bakkenolide A is presented from the readily available optically active Wieland-Miescher ketone. This novel synthesis of this sesquiterpene lactone features the following as key stereoselective transformations: (i) the ring contraction reaction of a octalone mediated by thallium(III) nitrate (TTN); (ii) a hydrogenation to create the cis-fused junction; and (iii) the formation of the C7 quaternary center through an enolate intermediate. Furthermore, during this work, the absolute configuration of a trinorsesquiterpene isolated from Senecio Humillimus was assigned.

The soft nucleophilicity of organotellurolates driving the S(N)2-type lactone ring-opening reaction

Lithium and magnesium organotellurolates were reacted with lactones producing the corresponding tellurocarboxylic acids. Treatment of the reaction mixture with lithium aluminum hydride allowed the isolation of the corresponding hydroxytellurides in a one-pot operation. (C) 2009 Published by Elsevier Ltd

Practical synthesis of chiral beta-telluro amines by ring-opening reaction of aziridines

A set of chiral beta-tellurium amines and their selenium and sulfur-containing derivatives have been efficiently synthesized in good to excellent yields via the ring-opening reaction of chiral aziridines by chalcogen nucleophilic species. (C) 2008 Elsevier B.V. All rights reserved.

Iodine(III)-promoted ring expansion of 1-vinylcycloalkanol derivatives: A metal-free approach toward seven-membered rings

A versatile and metal-free approach for the synthesis of molecules bearing seven- and eight-membered rings is described. The strategy is based on the ring expansion of 1-vinylcycloalkanols (or the corresponding silyl or methyl ether) mediated by the hypervalent iodine reagent HTIB (Phl(OH)OTs). The reaction condition can be easily adjusted to give seven-membered rings bearing different functional groups. A route to medium-ring lactones was also developed.

Ring Contraction of 1,2-Dihydronaphthalenes Promoted by Thallium(III) in Acetonitrile: A Diastereoselective Approach to Indanes

trans-1,3-Disubstituted indanes are conveniently accessed by a stereoselective ring contraction of 1,2-dihydronaphthalenes upon treatment with thallium(III) nitrate (TTN) in acetonitrile. Under these conditions, the oxidative rearrangement of either di- or trisubstituted double bonds is possible.

A Diastereoselective Total Synthesis of trans-Trikentrin A: A Ring Contraction Approach

A new route to obtain the polyalkylated indole (+/-)-trans-trikentrin A was developed. The synthesis of this natural alkaloid features a thallium(III)mediated ring contraction reaction to obtain the trans-1,3-disubstituted five-membered ring in a diastereoselective manner. Thallium(III) is chemoselective in this rearrangement, reacting with the olefin without oxidation of the indole moiety. Other key transformations are the Bartoli`s reaction to construct the heterocyclic ring and a Heck coupling to add the carbons atom that will originate the nonaromatic cycle.

Mild and efficient one-pot synthesis of chiral beta-chalcogen amides via 2-oxazoline ring-opening reaction mediated by indium metal

A simple and efficient procedure for the synthesis of beta-seleno and beta-thio amides via the ring-opening reaction of chiral 2-oxazolines in the presence of indium metal has been developed. Features of this method include the following: (i) easily and accessible starting materials; (ii) indium metal is more stable and less expensive then its respective salts; (iii) useful to excellent yields of beta-chalcogen amides derivatives. (C) 2008 Elsevier B. V. All rights reserved.

An epoxide ring-opening approach for a short and stereoselective synthesis of icetexane diterpenoids

A new approach for the synthesis of the core skeleton of icetexane diterpenoids is presented and deals with an epoxide ring-opening reaction by metallated aromatic compounds. Employing this strategy, a short synthesis of an icetexane analogue of brussonol was achieved in just four steps from 2-allyl-cyclohexanone. (C) 2009 Elsevier Ltd. All rights reserved.

An insight into the beginning stage of the aqueous ring opening metathesis polymerization of exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid with Ru(III) compounds: the consumption of Ru(III) species in the presence of carboxylic acids monitored by ESR spectroscopy

The presence of paramagnetic species in the aqueous ring opening metathesis polymerizations of the exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid monomer with RuCl(3) and K(2)[RuCl(5)H(2)O] compounds was studied using ESR techniques. It was observed that the intensities of the Ru(III) signals in the ESR spectra decrease on the time scale of the induction period so that the ROMP can take place. The intensity of the Ru(III) signal almost disappeared 50 min after reacting with K(2)[RuCl(5)H(2)O] and after 100 mm in the case of RuCl(3). Reactions of the cis-[Ru(NH(3))(4)(H(2)O)(2)](tfms)(3) and [Ru(NH(3))(5)H(2)O](tfms)(3) complexes with the monomer and different organic compounds representing the organic functions in the monomer (furan, norbornene, but-2-ene-1,4-diol and formic, acetic, oxalic and maleic acids) were also monitored by ESR and UV/vis spectra. It was deduced that the organic acids provide the disappearance of the Ru(III) signal. The proton NMR relaxation times of the residual water in D(2)O for reactions with oxalic acid suggested that the presence of paramagnetic ions in the solution decreases along with

Smärtlindring vid vaginal förlossning och dess samband med avslutad amning vid två månaders ålder

Bakgrund: Smärtlindring under förlossning och amning är två stora kompetensområden inom barnmorskans profession vilket medför att barnmorskan bör ha kunskap om eventuella samband mellan olika smärtlindringsmetoder och amning. Tidigare forskning om smärtlindringsmetoder och dess samband med amning har oftast fokuserat på enstaka smärtlindringsmetoder samt belyst sambandet med amningsinitiering efter förlossningen. Studier saknas således där hela spektrumet av smärtlindringsmetoder och dess samband med amning fram till två månaders ålder studeras. Syfte: Att undersöka förekomst av smärtlindringsmetoder under vaginal förlossning av fullgångna barn, vilka faktorer som är associerade med respektive smärtlindringsmetod samt eventuella samband mellan smärtlindringsmetod och amning vid två månaders ålder. Metod: Populationsbaserad, prospektiv kohort studie där 31 150 moder-barn par i Uppsala och Örebro län ingick. Material inhämtades från Medicinska Födelseregistret, Statistiska Centralbyrån samt Barnhälsovården. Statistiska analyser inkluderade Chi-två test, binär logistisk regressionsanalys samt multivariat logistisk regressionsanalys. Resultat: Inhalation av lustgas var den mest använda smärtlindringsmetoden. Användningen av smärtlindringsmetoder hade flest samband med län, etnicitet, paritet och moderns ålder. Risken för användning av epiduralblockad var nästan sex gånger så hög för förstföderskor. Intramuskulära injektioner med petidin/morfin eller epiduralblockad medförde en risk för avslutad amning innan två månaders ålder, men för TENS ochakupunktur fanns ett samband med fortsatt amning vid två månaders ålder. Slutsats: Det finns ett samband mellan smärtlindringsmetod och amning två månader postpartum. Barnmorskor bör ha kunskap om detta samband för att kunna stödja mödrarnas val av smärtlindringsmetod och amningsutfall.

Amningsduration vid sectio och vaginalförlossning : Breastfeeding duration at cesarean section and vaginal delivery. Apopulationbased register study.

Bakgrund: Amning är av stor betydelse för det nyfödda barnet och mamma, både ur närings- och trygghetsaspekter. Tidigare studier om sambandet mellan förlossningssätt och amning visar motstridiga resultat; vissa studier indikerar att sectio påverkar amningen negativt medan andra studier inte visar på något samband.Syftet: Att undersöka huruvida det finns demografiska och hälsorelaterade skillnader hos mammor gällande förlossningssätt samt om förlossningssätt påverkar amningsdurationen upp till två månaders ålder.Metod: Studien har en populationsbaserad kohortdesign och omfattar n= 35250 mamma-barn par i Örebro- och Uppsala län, där barnet fötts åren 1993-2001. Statistiska analyser har genomförts med Chi-square test, binär logistisk regressionsanalys och multivariat logistik regressionsanalys.Resultat: Visade att mammor som förlösts med sectio ammade i lägre utsträckning vid två månaders ålder i jämförelse med mammor som förlösts vaginalt. Många riskfaktorer identifierades för en ökad risk att förlösas med sectio: län, hälsofaktorer hos mamma och barn, paritet, mammans ålder, rökning samt socioekonomiska faktorer. Resultatet kan hjälpa barnmorskan i hennes profession, genom att kunskap erhålls om dessa samband. Barnmorskan kan därmed identifiera riskfaktorer, arbeta förebyggande och underlätta initieringen av amning.Konklusion: Barnmorskor kan med hjälp av denna studie öka medvetenheten hos vårdpersonal angående sectioförlösta mammors behov av extra stöd vid initiering av amning.

Thomas-Fermi ground state of dipolar fermions in a circular storage ring

Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

Superconducting state in a mesoscopic segment ring

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aharonov-Bohm oscillations in a quantum ring: Eccentricity and electric-field effects

The effects of an in-plane electric field and eccentricity on the electronic spectrum of a GaAs quantum ring in a perpendicular magnetic field are studied. The effective-mass equation is solved by two different methods: an adiabatic approximation and a diagonalization procedure after a conformal mapping. It is shown that the electric field and the eccentricity may suppress the Aharonov-Bohm oscillations of the lower energy levels. Simple expressions for the threshold energy and the number of flat energy bands are found. In the case of a thin and eccentric ring, the intensity of a critical field which compensates the main effects of eccentricity is determined. The energy spectra are found in qualitative agreement with previous experimental and theoretical works on anisotropic rings.