Asymmetric synthesis of arylalanines via asymmetric aza-darzens (ADZ) reaction

(R)-3-Arylalanines may be prepared in high enantiomeric purity from N-dpp imines by a four-step reaction sequence involving asymmetric aza-Darzens reaction, dephosphinylation, hydrogenolysis and hydrolysis. The amino acids thus obtained were of >95% enantiomeric purity.

Sequential ring-closing metathesis and nitrone cycloaddition on glucose-derived substrates: a divergent approach to analogues of spiroannulated carbanucleosides and conformationally locked nucleosides

The carbohydrate-derived substrate 3-C-allyl-1,2: 5,6-di-O-isopropylidene-alpha-D-allofuranose was judiciously manipulated for preparing suitable synthons, which could be converted to a variety of isoxazolidino-spirocycles and -tricycles through the application of ring-closing metathesis (RCM) and intramolecular nitrone cycloaddition (INC) reactions. Cleavage of the isoxazolidine rings of some of these derivatives by tranfer hydrogenolysis followed by coupling of the generated amino functionalities with 5-amino-4,6-dichloropyrimidine furnished the corresponding chloropyrimidine nucleosides, which were elaborated to spiroannulated carbanucleosides and conformationally locked bicyclo[2.2.1] heptane/ oxa-bicyclo[3.2.1]octane nucleosides. However, use of higher temperature for the cyclization of one of the chloropyrimidines led to the dimethylaminopurine analogue as a sole product, formed via nucleophilic displacement of the chloro group by dimethylamine generated from DMF.

Synthesis of oxepane ring containing monocyclic, conformationally restricted bicyclic and spirocyclic nucleosides from d-glucose: a cycloaddition approach

Carbohydrate-derived substrates having (i) C-5 nitrone and C-3-O-allyl, (ii) C-4 vinyl and a C-3-O-tethered nitrone, and (iii) C-5 nitrone and C-4-allyloxymethyl generated tetracyclic isoxazolidinooxepane/-pyrart ring systems upon intramolecular nitrone cycloaddition reactions. Deprotection of the 1,2acetonides of these derivatives followed by introduction of uracil base via Vorbruggen reaction condition and cleavage of the isooxazolidine rings as well as of benzyl groups by transfer hydrogenolysis yielded an oxepane ring containing blicyclic and spirocyclic nucleosides. The corresponding oxepane based nucleoside analogues were prepared by cleavage of isoxazolidine and furanose rings, coupling of the generated amino functiontalities with 5-amino-4,6-dichloropyrimidine, cyclization to purine rings, and finally aminolysis.

Surface science studies of strong metal-oxide interactions on model catalysts

The strong metal support interaction (SMSI) was first described in 1978 by Tauster [1-4]. The effect was observed as a severely negative effect on CO and H2 uptake on the catalyst after high temperature calcination under reducing conditions (heating above ~ 700 K) [1,2]. It also had a negative effect on the reaction rate for reactions, such as alkane hydrogenolysis [5,6]. It appeared that the effect occurred for catalysts comprised of reducible supports which were treated at elevated temperature in reducing conditions [2-4]. A classic support which has manifested this behaviour in many studies is TiO2. Over the years following the first discovery of SMSI it has been recognised that the effect is not always negative ��� for instance for the CO-H2 reaction for which it appears to have a positive effect [5,6]. Further it was noted that hydrogen reduction was not necessary to observe the effect of CO adsorption suppression, it also occurs by vacuum treatment [7], though it should be noted that vacuum treatment at elevated temperature is, in effect, a reducing environment.

Rhythmic behavior of social insects from single to multibody

Revealing the evolution of well-organized social behavior requires understanding a mechanism by which collective behavior is produced. A well-organized group may be produced by two possible mechanisms, namely, a central control and a distributed control. In the second case, local interactions between interchangeable components function at the bottom of the collective behavior. We focused on a simple behavior of an individual ant and analyzed the interactions between a pair of ants. In an experimental set-up, we placed the workers in a hemisphere without a nest, food, and a queen, and recorded their trajectories. The temporal pattern of velocity of each ant was obtained. From this bottom-up approach, we found the characteristic behavior of a single worker and a pair of workers as follows: (1) Activity of each individual has a rhythmic component. (2) Interactions between a pair of individuals result in two types of coupling, namely the anti-phase and the in-phase coupling. The direct physical contacts between the pair of workers might cause a phase shift of the rhythmic components in individual ants. We also build up a simple model based on the coupled oscillators toward the understanding of the whole colony behavior.

Modeling the patrol behavior of the Diacamma's gamergate

The gamergate (generally called the ���queen���) of the Diacamma sp. walks around in the nest and comes into contact with the workers. The gamergate informs the workers of its presence by physical contact. This behavior is called a ���patrol.��� In previous work, it was reported that the gamergate controls its patrolling time depending on the colony size. How does the gamergate know the colony size, and how does it control the patrolling time? In this article, we propose a simple dynamics to explain this behavior. We assume that the gamergate and the workers have internal states which interact by physical contacts. By numerical simulations, we confirm that the patrol time of the proposed model depends on the size of the colony.

Analysis and modeling of ants��� behavior from single to multi-body

In order to shed light on the collective behavior of social insects, we analyzed the behavior of ants from single to multi-body. In an experimental set-up, ants are placed in hemisphere without a nest and food. Trajectory of ants is recorded. From this bottom-up approach, we found that collective behavior of ants as follows: 1. Activity of single ant increases and decreases periodically. 2. Spontaneous meeting process is observed between two ants and meeting spot of two ants is localized in hemisphere. 3. Result on division of labor is obtained between two ants.

Effect of pair interactions on transition probabilities between inactive and active states: achieving collective behaviour via pair interactions in social insects

To understand the evolution of well-organized social behaviour, we must first understand the mechanism by which collective behaviour establishes. In this study, the mechanisms of collective behaviour in a colony of social insects were studied in terms of the transition probability between active and inactive states, which is linked to mutual interactions. The active and inactive states of the social insects were statistically extracted from the velocity profiles. From the duration distributions of the two states, we found that 1) the durations of active and inactive states follow an exponential law, and 2) pair interactions increase the transition probability from inactive to active states. The regulation of the transition probability by paired interactions suggests that such interactions control the populations of active and inactive workers in the colony.

Multicenter Analysis of Glucocerebrosidase Mutations in Parkinson`s Disease

Background Recent studies indicate an increased frequency of mutations in the gene encoding glucocerebrosidase (GBA), a deficiency of which causes Gaucher`s disease, among patients with Parkinson`s disease. We aimed to ascertain the frequency of GBA mutations in an ethnically diverse group of patients with Parkinson`s disease. Methods Sixteen centers participated in our international, collaborative study: five from the Americas, six from Europe, two from Israel, and three from Asia. Each center genotyped a standard DNA panel to permit comparison of the genotyping results across centers. Genotypes and phenotypic data from a total of 5691 patients with Parkinson`s disease (780 Ashkenazi Jews) and 4898 controls (387 Ashkenazi Jews) were analyzed, with multivariate logistic-regression models and the Mantel-Haenszel procedure used to estimate odds ratios across centers. Results All 16 centers could detect two GBA mutations, L444P and N370S. Among Ashkenazi Jewish subjects, either mutation was found in 15% of patients and 3% of controls, and among non-Ashkenazi Jewish subjects, either mutation was found in 3% of patients and less than 1% of controls. GBA was fully sequenced for 1883 non-Ashkenazi Jewish patients, and mutations were identified in 7%, showing that limited mutation screening can miss half the mutant alleles. The odds ratio for any GBA mutation in patients versus controls was 5.43 across centers. As compared with patients who did not carry a GBA mutation, those with a GBA mutation presented earlier with the disease, were more likely to have affected relatives, and were more likely to have atypical clinical manifestations. Conclusions Data collected from 16 centers demonstrate that there is a strong association between GBA mutations and Parkinson`s disease.

Measurement of the Viscoelastic Properties of the Vocal Folds

Objectives: Studies of the viscoelastic properties of the vocal folds are normally performed with rheometers that use parallel assigned a fixed value. In tissues subject to variation of thickness plates whose interplate space is usually at between samples, fixed gaps could result in different compressions, compromising the comparison among them. We performed,in experimental study to determine whether different compressions call lead to different results in measurements of dynamic viscosity (DV) of vocal fold samples. Methods: We Measured the DV of vocal fold samples of 10 larynges of cadavers under 3 different compression levels, corresponding to 0.2, 0.5, and 10 N on an 8-mm-diameter parallel-plate rheometer. Results: The DV directly varied with compression. We observed statistically significant differences between the results of 0.2 and 10 N (p = 0.0396) and 0.5 and 10 N (p = 0.0442). Conclusions: The study demonstrated that the level of compression influences the DV measure and Suggests that a defined compression level should be used in rheometric studies of biological tissues.

Equipes globais virtuais : a expeir��ncia de profissionais em banco de investimentos multinacionais

Iniciado nos anos de 1960, o segundo est��gio do processo de globaliza����o, liderado principalmente pelas empresas multinacionais e suas estrat��gias de expans��o, e suportado pelos avan��os da tecnologia de informa����o e comunica����o, resultou em profundas transforma����es nas estruturas organizacionais, que passaram de modelos hierarquizados em detrimento de modelos mais flex��veis e din��micos, mudando a maneira de trabalhar. Este projeto objetivou estudar o impacto decorrente da utiliza����o de estruturas organizacionais baseadas em redes globais e equipes globais virtuais nos profissionais que atuam em bancos de investimento multinacionais. Os impactos foram avaliados atrav��s do conceito de descontinuidade, que �� entendido como fator ou fatores que contribuem para falta de coes��o em situa����es de coletividade. Foram analisados 15 profissionais, de 4 bancos de investimentos multinacionais, e aplicaram-se entrevistas individuais presenciais formuladas considerando as descontinuidades e itens propostos na literatura (Duarte e Snyder, 1999; Watson-Manheim et al., 2002; Espinosa et al., 2003; Saunders et al., 2004; Jarvenpaa et al., 2004; Zolin et al., 2004; Golden e Veiga, 2005; Chudoba et al., 2005; Dani et al., 2006) para investiga����o. Os resultados das an��lises dos dados coletados permitem inferir que os fatores de descontinuidade sugeridos no estudo s��o relevantes aos profissionais de banco de investimentos multinacionais. Adicionalmente, percebe-se que apesar de coletadas e analisadas individualmente, h�� correla����o entre as descontinuidades analisadas, com incid��ncia conjunta ou simult��nea no desempenho das atividades dos profissionais.

Gerenciamento de risco e valor no Brasil : um estudo emp��rico

Este trabalho examina a rela����o entre a volatilidade do fluxo de caixa operacional e o valor da firma, utilizando como amostra empresas brasileiras n��o financeiras listadas na Bolsa de Valores de S��o Paulo (Bovespa), no per��odo de 2004 a 2007. O estudo aplica duas metodologias distintas para garantir a robustez dos resultados. Embora os resultados apontem que empresas com menor volatilidade do fluxo de caixa possuem maior valor, os valores encontrados n��o se mostram significativos.

A resposta metab��lica ao trauma cranioencef��lico �� autolimitada? An��lise das prote��nas de fase aguda e glicemia

Nos ��ltimos anos tem havido refer��ncias �� limita����o da resposta metab��lica nas duas primeiras semanas ap��s trauma cranioencef��lico (TCE). Foi feita proposta de estudo a partir de experimento cl��nico em pacientes com trauma encef��lico grave, que foram avaliados por volta de 7 dias ap��s a les��o (M1). A segunda avalia����o ocorreu 4 dias ap��s (M2), e a terceira 3 a 4 dias ap��s (M3). em um per��odo de 2 anos, foram selecionados 28 pacientes do sexo masculino, com trauma encef��lico grave, escala de gravidade de Glasgow entre 4 e 6. Dentre os 28 pacientes, 6 completaram o estudo proposto. Os pacientes foram acompanhados clinicamente durante toda a fase do experimento. em cada um dos momentos de an��lise, foram feitas an��lises da excre����o nitrogenada e prote��nas de fase aguda. da mesma forma foram feitas determina����es da glicemia plasm��tica, N-am��nico e triglicer��deos. Os resultados do estudo demonstraram n��o haver modifica����es no balan��o nitrogenado, normaliza����o da prote��na-C-reativa e redu����o relativa da glicemia ao final do experimento. Os autores tecem considera����es sobre os poss��veis mecanismos envolvidos na modula����o da resposta metab��lica e concluem que o hipermetabolismo, a basear-se na an��lise da glicemia e das prote��nas de fase aguda, n��o persiste al��m do 13�� dia do per��odo de recupera����o p��s-trauma. S��o feitas sugest��es de estudos futuros que possam elucidar os mecanismos envolvidos na normaliza����o do hipercatabolismo e hipermetabolismo observados nas duas primeiras semanas ap��s TCE.

Frequency of human leukocyte antigen (hla) in patients with malaria and in the general population of Humait�� county, Amazonas state, Brazil

Em agosto de 1983 foram observados 85 habitantes do Munic��pio de Humait��, Estado do Amazonas, Brasil, com a finalidade de estudar a preval��ncia dos ant��genos de HLA -A, -B, -C e DR, dentre os quais 38 eram doentes com mal��ria causada pelo Plasmodium falciparum Todos eles foram examinados para avalia����o de esplenomegalia, exame parasitol��gico de sangue e pesquisa de anticorpos de mal��ria. Foram constitu��dos tr��s grupos: (I) 25 indiv��duos nascidos na regi��o Amaz��nica que nunca tiveram mal��ria; (II) 38 indiv��duos naturais da Amaz��nia que tinham sido tratados de mal��ria no passado, ou que estavam tendo mal��ria atual, e (III) 22 doentes com mal��ria que contra��ram na Amaz��nia e eram procedentes de outras regi��es do Brasil. Foram colhidas amostras de sangue de cada um deles, separados os linf��citos e os ant��genos de HLA foram tipados pelo teste de microlinfocitotoxidade. Houve elevada freq����ncia de ant��genos n��o identificados, nos grupos estudados, o que sugere ou a exist��ncia de homozigoze, oufen��tipo n��o identificado nessa popula����o. Houve alta freq����ncia fenot��pica de ant��geno deAg(W24) (44,7%) no Grupo II, quando comparado ao Grupo 1(32%) ou Grupo III (9%). Os indiv��duos do Grupo II mostraram tamb��m elevada freq����ncia do ant��geno DR4 (80%) quando comparado ao Grupo 1(36,3%) ou Grupo III(16,6%). Essas observa����es sugerem a possibilidade de suscetibilidadegen��tica �� mal��ria entre os nativos da Amaz��nia e indicam a necessidade da realiza����o de inqu��ritos mais extensos sobre a freq����ncia de ant��genos de HLA em habitantes de zona end��mica de mal��ria.