984 resultados para 3-R-Konzept


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A convenient asymmetric total synthesis of the potent HIF-1 inhibitory antitumor natural product, (−)- or (+)-(8R)-mycothiazole (1), is described. Not only does our synthesis confirm the 2006 structural reassignment made by Crews (Crews, P., et al. J. Nat. Prod. 2006, 69, 145), it revises the [α]D data previously reported for this molecule in MeOH from −13.7° to +42.3°. The newly developed route to (8R)-1 sets the C(8)–OH stereocenter via Sharpless AE/2,3-epoxy alcohol reductive ring opening and utilizes two Baldwin–Lee CsF/cat. CuI Stille cross-coupling reactions with vinylstannanes 8 and 3 to efficiently elaborate the C(1)–C(4) and C(14)–C(18) sectors.

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Dissertação para obtenção do Grau de Mestre em Auditoria

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Dissertação apresentada ao Instituto Superior de Contabilidade para a obtenção do Grau de Mestre em Auditoria Orientador: Mestre Agostinho Sousa Pinto

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Brown sediment with clasts ranging from small to large. The grain shape ranges from angular to sub-rounded. Rotation structures are abundant in this sample, along with necking structures. Some lineations and comet structures can also be seen. Crushed grains and grain stacks are present in minor amounts.

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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

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SAP R/3 és un software estàndard de gestió empresarial que engloba tots els processos i activitats d’una companyia i permet el disseny de l’aplicació a les necessitats de l’empresa. Diferents avantatges, com ara disposar d’una base de dades única, han fet escollir aquest sistema a una empresa del sector metal·lúrgic com a eina de gestió: Aquest projecte té com a objecte la implantació de dos dels mòduls que inclou el sistema SAP R/3, concretament el mòdul SD (Sales and Distribution), amb el qual es controlen les vendes de l’empresa, i el mòdul MM (Material Management), mòdul amb el qual es controla tot el que fa referència als materials, la gestió d’estocs i tota la gestió de compres de l’empresa

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Two novel, monomeric heteroleptic tin(II) derivatives, [Sn{2-[(Me3Si)2C]C5H4N}R] [R = C6H2Pri3-2,4,6 1 or CH(PPh2)2 2], have been prepared, characterised by multinuclear NMR spectroscopies and their molecular structures determined by single crystal X-ray diffraction. Both compounds were prepared from the corresponding heteroleptic tin(II) chloro-analogue, [Sn{2-[(Me3Si)2C]C5H4N}Cl], and thus demonstrate the utility of this compound as a precursor to further examples of heteroleptic tin(II) derivatives: such compounds are often unstable with respect to ligand redistribution. In each case, the central tin(II) is three-co-ordinate. Crystals of trimeric [{Sn(C6H2Pri3-2,4,6)2}3] 3 were found to undergo a solid state phase transition, which may be ascribed to ordering of the ligand isopropyl groups. At 220 K the unit cell is orthorhombic, space group Pna21, compared with monoclinic, space group P21/c, for the same crystals at 298 K, in which there is an effective tripling of the now b (originally c) axis. This result illustrates the extreme crowding generated by this bulky aryl ligand.

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Peculiar reduction pathways of the complexes fac-[Re(imH)(CO)3(phen)]+ and fac-[Re(imCH3)(CO)3(phen)]+ (imH = imidazole, imCH3 = N-methylimidazole and phen = 1,10-phenanthroline) have been unravelled by performing combined cyclic voltammetric and in situ IR spectroelectrochemical experiments. In the temperature range of 293–233 K, the initial reduction of the phen ligand in [Re(imH)(CO)3(phen)]+ results in irreversible conversion of the imidazole ligand to 3-imidazolate by a rapid phen•−→ imH intramolecular electron transfer coupled with N H bond cleavage. This process is followed by second phen-localized 1e− reduction producing [ReI(3-im−)(CO)3(phen•−)]−, similar to the analogous 2,2'-bipyridine complex. In contrast to the bpy analogue, the stability of the phen•−-containing complexes is significantly affected by lowering the temperature. At 233 K, a secondary reaction occurs in both [Re(3-im−)(CO)3(phen•−)]− and [Re(imCH3)(CO)3(phen•−)]. The resulting products exhibit v(CO) wavenumbers indistinguishable from those of the parent phen•− complexes; however, their oxidation occurs at a considerably more positive electrode potential. It is proposed that these species are produced by a new C C bond formation between the C(2) site of 3-im− or imCH3 and the C(2) site of the phen•−ligand.

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The Plant–Craig stochastic convection parameterization (version 2.0) is implemented in the Met Office Regional Ensemble Prediction System (MOGREPS-R) and is assessed in comparison with the standard convection scheme with a simple stochastic scheme only, from random parameter variation. A set of 34 ensemble forecasts, each with 24 members, is considered, over the month of July 2009. Deterministic and probabilistic measures of the precipitation forecasts are assessed. The Plant–Craig parameterization is found to improve probabilistic forecast measures, particularly the results for lower precipitation thresholds. The impact on deterministic forecasts at the grid scale is neutral, although the Plant–Craig scheme does deliver improvements when forecasts are made over larger areas. The improvements found are greater in conditions of relatively weak synoptic forcing, for which convective precipitation is likely to be less predictable.

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Let f : U subset of R(2) -> R(3) be a representative of a finitely determined map germ f : (R(2), 0) -> (R(3), 0). Consider the curve obtained as the intersection of the image of the mapping f with a sufficiently small sphere s(epsilon)(2) centered at the origin in R(3), call this curve the associated doodle of the map germ f. For a large class of map germs the associated doodle has many transversal self-intersections. The topological classification of such map germs is considered from the point of view of the associated doodles. (C) 2009 Elsevier Inc. All rights reserved.