Substâncias enantiomericamente puras (SEP): a questão dos fármacos quirais

The thalidomide disaster, in the 60,s, is the most painful reminder of the importance of chirality for biological activity. After this episode, much attention has been devoted to study the correlations between toxicological and pharmacological properties and chirality. Actualy, to get a licence for a new chiral drug in EUA, European community and Japan, it is necessary to study the biological properties of each enatiomer independently. This article presents an overview about the importance of the chirality of organic compounds and its relationships with biological activity, asymmetric synthetic methodologies and market.

Unsaturated Oxazolopiperidone Lactams: an Unexpected Domino-type Double Conjugate Additioncyclization Process

Reactions of 2-acetylindole enolate with unsaturated oxazolopiperidones 3, 4 and 10 unexpectedly gives pentacyclic dilactams 6, 7 and 11, respectively, resulting from a domino-type process involving two successive conjugate additions and a final cyclization.

Abordagens em síntese assimétrica

The approaches in asymmetric synthesis as the chiron approach, chiral auxiliaries, chiral reagents and asymmetric catalysis are described in a simplified way.

Time-varying Risk Premiums and Conditional Market Risk: Empirical Evidence from European Stock Markets

This study investigates the relationship between the time-varying risk premiums and conditional market risk in the stock markets of the ten member countries of Economy and Monetary Union. Second, it examines whether the conditional second moments change over time and are there asymmetric effects in the conditional covariance matrix. Third, it analyzes the possible effects of the chosen testing framework. Empirical analysis is conducted using asymmetric univariate and multivariate GARCH-in-mean models and assuming three different degrees of market integration. For a daily sample period from 1999 to 2007, the study shows that the time-varying market risk alone is not enough to explain the dynamics of risk premiums and indications are found that the market risk is detected only when its price is allowed to change over time. Also asymmetric effects in the conditional covariance matrix, which is found to be time-varying, are clearly present and should be recognized in empirical asset pricing analyses.

2-oxazolinas quirais: algumas aplicações como indutores de assimetria em reações orgânicas

This article summarizes how chiral 2-oxazolines have been employed as inducers of asymmetry in many kinds of organic reactions, including the more recent examples reported in which chiral bis(oxazolines) have been complexed in situ with transition metals and utilized to induce the stereoselectivity of some reactions.

Exits - Pääomasijoittajan irtautumisvaihtoehtojen juridista tarkastelua

Pääomasijoittaminen on Suomessa verrattain uusi ilmiö. Tutkielman tarkoitus on ollut tarkastella pääomasijoittajan irtautumista kohdeyhtiöstä juridisesta näkökulmasta. Tutkielman ydin on ollut selvittää pääomasijoittamisen toimijoiden roolien ja niistä johtuvien intressien ristiriitojen vaikutusta irtautumiseen sekä sitä, miten intressiristiriitoja vähennetään erityisesti pääomasijoittajan näkökulmasta. Teoreettisena viitekehyksenä on käytetty päämies-agenttiteoriaa sekä teoriaa asymmetrisestä tiedosta ja moraalisesta uhkapelistä. Toisena tutkimusongelmana on selvitetty pääomasijoittamisen sijoittumista eri oikeudenalojen yhtymäkohtaan sekä luotu katsaus yleisesti pääomasijoittamista koskevaan lainsäädäntöön. Keskeisenä tavoitteena on ollut selvittää, aiheuttaako amerikkalaiseen sopimusmalliin perustuva sopimuskäytäntö ongelmia suomalaisessa juridisessa ympäristössä. Tutkimus on oikeustaloustieteellinen ja tutkimuskohteeseen on tutustuttu alan koti- ja ulkomaisen tutkimuksen ja kirjallisuuden lisäksi teemahaastatteluin. Tutkielman loppupäätelmä on, että pääomasijoittajan irtautumisen turvaamiseksi käytetään juridisesti tehokkaita menetelmiä, joista osakassopimuksen ehdot ovat ennemminkin ennaltaehkäiseviä kuin korjaavia. Intressiristiriitaa vähentämään käytetään myös kannustinjärjestelmä (osakeomistusta, optio-oikeuksia). Tutkimuksessa ei havaittu merkittäviä ongelmia amerikkalaisen sopimusmallin soveltamisessa suomalaiseen käytäntöön.

Catálise de transferência de fase

Since its discovery, phase transfer catalysis (PTC) has grown considerably and nowadays is one of the most versatile preparative methods. The search for new catalysts, their use in PTC asymmetric synthesis and the attempts to understand their mechanistic role are modern and exciting topics of investigation. A review on main achievements in the last two decades is presented.

Álcoois quirais: métodos químicos e catalíticos de obtenção por redução assimétrica

The importance of chiral alcohols as starting materials for the production of fine chemicals and as useful chirons for the building of several interesting molecules or natural products is reported. The useful and common methods of asymmetric reduction such as the chemical (with organoboron or organoaluminum reagents) and the catalytic ones (with ruthenium or rhodium complexes) for preparation of chiral alcohols are described; even the newer and much more rare electrocatalytic methods are reported.

Reações aldólicas assimétricas catalíticas

This review describes the use of catalytic asymmetric aldol reactions of silyl enol ethers and silyl (thio)ketene acetals with aldehydes (the Mukaiyama aldol reaction) in order to illustrate its synthetic utility. A variety of Lewis acid and basic reagents were employed for catalytic aldol reactions with high diastereo- and enantioselectivities. The origins of the selectivity of these reactions are discussed and some representative examples of their application in the synthesis of natural products are presented. New developments in chiral heterobimettalic lanthanoid catalysis and enantioselective aldol reactions in aqueous media are also included.

Aspectos regio- e estereoquímicos da adição de Michael assimétrica via iminas quirais com centros estereogênicos pré-existentes

The asymmetric Michael addition reactions using chiral imines, under neutral conditions (deracemizing alkylation process), constitute one of the main methods for the stereocontrolled elaboration of quaternary carbon centers. This protocol is based on the conjugate addition of secondary chiral enamines to electron-deficient alkenes. The focus of this report deals with the discussion of regio- and stereochemical aspects of the deracemizing alkylation process concerning enamines bearing a resident chiral center.

Essays on pricing of risk and international linkage of Russian stock market

Last two decades have seen a rapid change in the global economic and financial situation; the economic conditions in many small and large underdeveloped countries started to improve and they became recognized as emerging markets. This led to growth in the amounts of global investments in these countries, partly spurred by expectations of higher returns, favorable risk-return opportunities, and better diversification alternatives to global investors. This process, however, has not been without problems and it has emphasized the need for more information on these markets. In particular, the liberalization of financial markets around the world, globalization of trade and companies, recent formation of economic and regional blocks, and the rapid development of underdeveloped countries during the last two decades have brought a major challenge to the financial world and researchers alike. This doctoral dissertation studies one of the largest emerging markets, namely Russia. The motivation why the Russian equity market is worth investigating includes, among other factors, its sheer size, rapid and robust economic growth since the turn of the millennium, future prospect for international investors, and a number of important major financial reforms implemented since the early 1990s. Another interesting feature of the Russian economy, which gives motivation to study Russian market, is Russia’s 1998 financial crisis, considered as one of the worst crisis in recent times, affecting both developed and developing economies. Therefore, special attention has been paid to Russia’s 1998 financial crisis throughout this dissertation. This thesis covers the period from the birth of the modern Russian financial markets to the present day, Special attention is given to the international linkage and the 1998 financial crisis. This study first identifies the risks associated with Russian market and then deals with their pricing issues. Finally some insights about portfolio construction within Russian market are presented. The first research paper of this dissertation considers the linkage of the Russian equity market to the world equity market by examining the international transmission of the Russia’s 1998 financial crisis utilizing the GARCH-BEKK model proposed by Engle and Kroner. Empirical results shows evidence of direct linkage between the Russian equity market and the world market both in regards of returns and volatility. However, the weakness of the linkage suggests that the Russian equity market was only partially integrated into the world market, even though the contagion can be clearly seen during the time of the crisis period. The second and the third paper, co-authored with Mika Vaihekoski, investigate whether global, local and currency risks are priced in the Russian stock market from a US investors’ point of view. Furthermore, the dynamics of these sources of risk are studied, i.e., whether the prices of the global and local risk factors are constant or time-varying over time. We utilize the multivariate GARCH-M framework of De Santis and Gérard (1998). Similar to them we find price of global market risk to be time-varying. Currency risk also found to be priced and highly time varying in the Russian market. Moreover, our results suggest that the Russian market is partially segmented and local risk is also priced in the market. The model also implies that the biggest impact on the US market risk premium is coming from the world risk component whereas the Russian risk premium is on average caused mostly by the local and currency components. The purpose of the fourth paper is to look at the relationship between the stock and the bond market of Russia. The objective is to examine whether the correlations between two classes of assets are time varying by using multivariate conditional volatility models. The Constant Conditional Correlation model by Bollerslev (1990), the Dynamic Conditional Correlation model by Engle (2002), and an asymmetric version of the Dynamic Conditional Correlation model by Cappiello et al. (2006) are used in the analysis. The empirical results do not support the assumption of constant conditional correlation and there was clear evidence of time varying correlations between the Russian stocks and bond market and both asset markets exhibit positive asymmetries. The implications of the results in this dissertation are useful for both companies and international investors who are interested in investing in Russia. Our results give useful insights to those involved in minimising or managing financial risk exposures, such as, portfolio managers, international investors, risk analysts and financial researchers. When portfolio managers aim to optimize the risk-return relationship, the results indicate that at least in the case of Russia, one should account for the local market as well as currency risk when calculating the key inputs for the optimization. In addition, the pricing of exchange rate risk implies that exchange rate exposure is partly non-diversifiable and investors are compensated for bearing the risk. Likewise, international transmission of stock market volatility can profoundly influence corporate capital budgeting decisions, investors’ investment decisions, and other business cycle variables. Finally, the weak integration of the Russian market and low correlations between Russian stock and bond market offers good opportunities to the international investors to diversify their portfolios.

Alilação e crotilação catalítica e enantiosseletiva de aldeídos

The field of chiral catalysis has experienced explosive growth over the last two decades. By now, many of the classical reactions in organic synthesis can be carried out efficiently in asymmetric manner. As one of the fundamental and powerful C-C bond-forming reactions, enantioselective catalytic allylation (ECA) and crotylation (ECC) of aldehydes has attracted considerable attention. In this article, we present an overview about the importance of chiral Lewis acids and bases in catalytic enantioselective addition of allyl- and crotyl metals to aldehydes and the application of this methodology in the total synthesis of natural and non-natural products.

Vladimir Prelog e a estereoquímica das moléculas orgânicas: um centenário de nascimento

The Croatian chemist Vladimir Prelog shared in 1975 the Nobel Prize in chemistry with J. W. Cornforth for his research into the stereochemistry of organic molecules and reactions. His studies gave new horizons to the comprehension of steric effects on the reactivity of medium-sized rings, to conformational analysis and to the stereospecificity associated to asymmetric syntheses. Prelog made important contributions to enzyme chemistry and to the structure elucidation of alkaloids and of antibiotics from microorganisms, but probably his most famous work is the CIP system for assigning the stereochemistry of chiral centers.

Catálise assimétrica na ciclopropanação de olefinas

The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Exemples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals.

Monoterpenos di-hidroxilados e hidróxi-nitrogenados 1,2 e 1,3 como ligantes quirais em reação de reformatsky assimétrica

This study describes the use of three (-)-alpha-pinene derivatives, one diol-1,2 [(-)-(1R, 2R, 3S, 5R)-2,6,6-trimethylbicyclo[3.1.1]heptane-2,3-diol 4] and two piridine-hydroxy derivatives [(+)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-(2-pyridinylmethyl)bicyclo[3.1.1]heptan-3-ol 7 and (-)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-[2-(2-pyridinyl) ethyl]bicyclo[3.1.1]heptan-3-ol 8]; one diol-1,3 [(-)-(1S,2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 5] derived from (+)-isopulegol 2 and one diol-1,3 [(+)-(1R,2R,5R)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 6] derived from (+)-neo-isopulegol 3, as ligands in the asymmetric Reformatsky reaction. The best enantiomeric excess of beta-hydroxy ester obtained in the Reformatsky asymmetric reaction was 18% using ligand 6, and the chemical yield of the reactions was 65% on average.