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Enantioselective Approaches and Domino Sequences for the Synthesis of Compounds of Biological Interest
No full textNeuropeptide S (NPS) is the endogenous ligand of the previously orphan G-protein coupled receptor, recently named NPSR.12 NPS is a small peptide of 20 amino acids and rapresents the endogenous ligand of NPSR. In cells expressing the recombinant NPSR receptor, NPS selectively binds and activates its receptor, producing intracellular calcium mobilization and an increase of cAMP levels. The NPS-NPSR receptor system regulates important biological functions such as sleep/waking, locomotion, anxiety and food intake. (R/S) SHA-68 21 is the first non-peptide antagonist of NPSR receptor; actually only a class of molecules able to interact with NPSR are reported in the literature and they are the same oxazol-piperazine structure. Initially, in order to confirm the published data, we decided to synthesize SHA 68 in racemic form following the Okamura’s methodology21. The high selectivity of (R/S)-SHA 68 for NPSR and its good antagonist activity prompted us to synthesize the enantiomers of this non-peptide compound, starting from cheap commercially available reagents as chiral auxiliary. In order to define the conformation of the piperazine ring in this two enantiomers we performed a series of NMR experiments leading to define a chair conformation where the substituent in C9 was placed in equatorial position. To know the absolute configuration of the new chiral centre X ray analysis was performed on suitable crystals that show us the R configuration of the new stereogenic centre. From a pharmacological point of view (R)-SHA 68 was demonstrated to be the antagonist of the receptor of the Neuropeptide S. This new class of non-peptide NPSR antagonists provides additional tools for in vitro and in vivo studies required to elucidate the NPSR conformation, adding new informations to well know NPS-NPSR system. In the frame of the synthesis of biological active chiral compounds I have spend nine months at the Pierre et Marie Curie University in Paris under the supervision of Professor Giovanni Poli, focusing the attention on the synthesis of natural product (-)- Steganacin. This stage allowed me to view a different approach for the selective generation of new structures using a palladium catalysed domino reactions instead of the use of chiral auxiliaries used for the synthesis of (R) and (S)-SHA 68. Steganacin was isolated from a plant of South Africa, Steganotaenia araliacea.31 The interest of chemists for the (-)-Steganacin was initially motivated by its antitumor activity; 34 it is for this reason that in literature we found different total syntheses of this molecule. From a structural point of view the (-)-Steganacine presents a γ-lactonic skeleton condensed to an eight membered ring, a biarylic portion and three contiguous stereogenic centers with a relative stereochemistry trans, trans. Aim of this project is the synthesis of an aza-analogue of Steganacine in which the lactone structure is replaced by a γ-lactam moiety. The synthetic process starts from a commercially available propargyl alcohol to afford in seven steps the desired cyclization precursor in 19 % yield. The key step of our project was previously studied in the laboratories of Prof. Giovanni Poli and reported in literature by Kammerer et al. in 2009.41 This is an original regioand stereoselective synthesis of aryl substituted pyrrolidones by a phosphine-free Pdcatalyzed allene carbopalladation/allylic alkylation sequence. This reaction allowed us to obtain the key intermediate in 74% yield. After benzylation of this key intermediate, several strategies to remove the methoxycarbonyl group were tested, the best solution being hydrolysis in ethylene glycol at high temperatures. The next study will focus on the non-phenolic oxidative coupling between the two aromatic moieties to formed an eight membered ring. Then, an oxidative cleavage of the double bond followed by a diastereoselective reduction of the resulting ketone and final alcohol acetylation should afford the desired (-)-Steganacin aza-analogue.Neuropeptide S (NPS) is the endogenous ligand of the previously orphan G-protein coupled receptor, recently named NPSR.12 NPS is a small peptide of 20 amino acids and rapresents the endogenous ligand of NPSR. In cells expressing the recombinant NPSR receptor, NPS selectively binds and activates its receptor, producing intracellular calcium mobilization and an increase of cAMP levels. The NPS-NPSR receptor system regulates important biological functions such as sleep/waking, locomotion, anxiety and food intake. (R/S) SHA-68 21 is the first non-peptide antagonist of NPSR receptor; actually only a class of molecules able to interact with NPSR are reported in the literature and they are the same oxazol-piperazine structure. Initially, in order to confirm the published data, we decided to synthesize SHA 68 in racemic form following the Okamura’s methodology21. The high selectivity of (R/S)-SHA 68 for NPSR and its good antagonist activity prompted us to synthesize the enantiomers of this non-peptide compound, starting from cheap commercially available reagents as chiral auxiliary. In order to define the conformation of the piperazine ring in this two enantiomers we performed a series of NMR experiments leading to define a chair conformation where the substituent in C9 was placed in equatorial position. To know the absolute configuration of the new chiral centre X ray analysis was performed on suitable crystals that show us the R configuration of the new stereogenic centre. From a pharmacological point of view (R)-SHA 68 was demonstrated to be the antagonist of the receptor of the Neuropeptide S. This new class of non-peptide NPSR antagonists provides additional tools for in vitro and in vivo studies required to elucidate the NPSR conformation, adding new informations to well know NPS-NPSR system. In the frame of the synthesis of biological active chiral compounds I have spend nine months at the Pierre et Marie Curie University in Paris under the supervision of Professor Giovanni Poli, focusing the attention on the synthesis of natural product (-)- Steganacin. This stage allowed me to view a different approach for the selective generation of new structures using a palladium catalysed domino reactions instead of the use of chiral auxiliaries used for the synthesis of (R) and (S)-SHA 68. Steganacin was isolated from a plant of South Africa, Steganotaenia araliacea.31 The interest of chemists for the (-)-Steganacin was initially motivated by its antitumor activity; 34 it is for this reason that in literature we found different total syntheses of this molecule. From a structural point of view the (-)-Steganacine presents a γ-lactonic skeleton condensed to an eight membered ring, a biarylic portion and three contiguous stereogenic centers with a relative stereochemistry trans, trans. Aim of this project is the synthesis of an aza-analogue of Steganacine in which the lactone structure is replaced by a γ-lactam moiety. The synthetic process starts from a commercially available propargyl alcohol to afford in seven steps the desired cyclization precursor in 19 % yield. The key step of our project was previously studied in the laboratories of Prof. Giovanni Poli and reported in literature by Kammerer et al. in 2009.41 This is an original regioand stereoselective synthesis of aryl substituted pyrrolidones by a phosphine-free Pdcatalyzed allene carbopalladation/allylic alkylation sequence. This reaction allowed us to obtain the key intermediate in 74% yield. After benzylation of this key intermediate, several strategies to remove the methoxycarbonyl group were tested, the best solution being hydrolysis in ethylene glycol at high temperatures. The next study will focus on the non-phenolic oxidative coupling between the two aromatic moieties to formed an eight membered ring. Then, an oxidative cleavage of the double bond followed by a diastereoselective reduction of the resulting ketone and final alcohol acetylation should afford the desired (-)-Steganacin aza-analogue
Petrology of suprasubductive mantle xenoliths from Estancia Sol De Mayo (Central Patagonia, Argentina)
No full textA new suite of mantle xenoliths from Estancia Sol de Mayo (Patagonia) has been investigated. They have been sampled and entrained by alkaline lavas from the south western corner of the Meseta Lago Buenos Aires. Chondrite-normalized trace element patterns of these lavas resemble that of the OIB, and of the main and post-plateau lavas from the Triple Junction Province. The xenoliths are mainly anhydrous spinel-bearing harzburgites and dunites, with minor lherzolites and one wehrlite. They are characterized by a coarse grained protogranular texture and devoid of modal metasomatic features. They show two texturally different clinopyroxenes. One is protogranular, defined cpx1, while the second is linked to the spinel (cpx2). Also three different orthopyroxenes are recognized: one is represented by large protogranular crystals with exsolution lamellae (opx1); the second by small clean and undeformed grains without exsolution lamellae (opx2) and the last occurs as smaller grains arranged in vein (opx3). On the whole the geochemical features of clinopyroxenes and orthopyroxenes major element compositions highlight three different trends. Two of them are in common between cpx and opx while the third is observed only for the cpx and is situated in between the other two trends. The trace element concentrations normalized to chondrite do not show any difference between cpx 1 and cpx 2 (characterized by prominent to slightly negative Nb, Zr and Ti anomalies and LREE enriched), but discriminate the three groups of orthopyroxenes: one is represented by the opx 3 characterized by a prominent positive Zr anomaly, while the other two show always prominent to slightly negative Ti and Zr anomalies and LREE depleted. The correlation between incompatible trace elements ((La/Yb)N and SrN) and Al2O3 for the cpx highlights the presence of refertilization/metasomatic events affecting the upper mantle beneath Estancia Sol de Mayo, because of the enrichment of the LREE and Sr correlated to a decreasing of the Al2O3 content. A tholeiitic and a transitional/alkaline melt have to be accounted for a refertilization and a metasomatic event, respectively. The comparison with other localities already studied highlights a global Al2O3 enrichment of the upper mantle from Patagonia. Also the pyroxenes from other Patagonian localities plot on the trends defined by the cpx and opx from Estancia Sol de Mayo. Moreover trace elements evidence metasomatic events affecting the mantle beneath some localities. Others are characterized only by partial melting events. Sr-Nd systematic performed for all the investigated localities show a large range of both 87Sr/86Sr and 143Nd/144Nd isotopic ratios that can be explained by a mixing between a depleted mantle and an enriched component (EM II).A new suite of mantle xenoliths from Estancia Sol de Mayo (Patagonia) has been investigated. They have been sampled and entrained by alkaline lavas from the south western corner of the Meseta Lago Buenos Aires. Chondrite-normalized trace element patterns of these lavas resemble that of the OIB, and of the main and post-plateau lavas from the Triple Junction Province. The xenoliths are mainly anhydrous spinel-bearing harzburgites and dunites, with minor lherzolites and one wehrlite. They are characterized by a coarse grained protogranular texture and devoid of modal metasomatic features. They show two texturally different clinopyroxenes. One is protogranular, defined cpx1, while the second is linked to the spinel (cpx2). Also three different orthopyroxenes are recognized: one is represented by large protogranular crystals with exsolution lamellae (opx1); the second by small clean and undeformed grains without exsolution lamellae (opx2) and the last occurs as smaller grains arranged in vein (opx3). On the whole the geochemical features of clinopyroxenes and orthopyroxenes major element compositions highlight three different trends. Two of them are in common between cpx and opx while the third is observed only for the cpx and is situated in between the other two trends. The trace element concentrations normalized to chondrite do not show any difference between cpx 1 and cpx 2 (characterized by prominent to slightly negative Nb, Zr and Ti anomalies and LREE enriched), but discriminate the three groups of orthopyroxenes: one is represented by the opx 3 characterized by a prominent positive Zr anomaly, while the other two show always prominent to slightly negative Ti and Zr anomalies and LREE depleted. The correlation between incompatible trace elements ((La/Yb)N and SrN) and Al2O3 for the cpx highlights the presence of refertilization/metasomatic events affecting the upper mantle beneath Estancia Sol de Mayo, because of the enrichment of the LREE and Sr correlated to a decreasing of the Al2O3 content. A tholeiitic and a transitional/alkaline melt have to be accounted for a refertilization and a metasomatic event, respectively. The comparison with other localities already studied highlights a global Al2O3 enrichment of the upper mantle from Patagonia. Also the pyroxenes from other Patagonian localities plot on the trends defined by the cpx and opx from Estancia Sol de Mayo. Moreover trace elements evidence metasomatic events affecting the mantle beneath some localities. Others are characterized only by partial melting events. Sr-Nd systematic performed for all the investigated localities show a large range of both 87Sr/86Sr and 143Nd/144Nd isotopic ratios that can be explained by a mixing between a depleted mantle and an enriched component (EM II)
Study, Modeling and Design of Semiconductor Photonic Crystal Based Devices
No full textThis thesis is focused on the study of nonlinear effects in semiconductor materials. The aim is the design of effcient optical devices able to supply ultra-fast high-performances all-optical signal processing. The goal is pur- sued by implementing different tools, either theoretical models as well as numerical methods. The main achievement is the design of new topologies for photonic crystal based devices that implement various optical functional- ities such as optical conversion and switching. This work has provided some confgurations for the manufacturing of a new generation of optical devices.This thesis is focused on the study of nonlinear effects in semiconductor materials. The aim is the design of effcient optical devices able to supply ultra-fast high-performances all-optical signal processing. The goal is pur- sued by implementing different tools, either theoretical models as well as numerical methods. The main achievement is the design of new topologies for photonic crystal based devices that implement various optical functional- ities such as optical conversion and switching. This work has provided some confgurations for the manufacturing of a new generation of optical devices
Competenze per il cambiamento organizzativo: Teorie, Metodi, Opportunità
No full textIn globalized markets, characterized by increasing uncertainty and highly dynamic competition, people have become, a crucial asset in order to support organizational change and competitiveness of companies. The increasing need of flexibility lead firms to the abandonment of “old” HRM systems, seen as too “bureaucratic” and inadequate to manage complex, rapidly evolving markets. Traditional job analysis practices, based on rigid tasks definitions and procedures, were progressively replaced by HR practices based on elements such as workers’ professionalism, creativity, reliability, knowledge, skills; in one word: on people’s competencies. The management of competencies has become a key challenge. Despite the many ambiguities and misunderstandings surrounding the debate on competencies, the development of Competency Based Human Resource System (CBHRS) seem to offer an opportunity to respond quickly and effectively to the current challenges that all kinds of organizations are facing. In this work we analyze and discuss the relationship between the “competency framework” and the issue of organizational change. Our hypothesis is that HR systems, based on the most diffused competency modeling practices, offer limited possibilities, for enacting significant – and not merely rhetorical – organizational changes. Through a literature review of available contributions on the subject, we will explore the key critiques to the mainstream positivist approach. In order to find empirical support to our hypothesis, examples from three case studies will be provided in order to both illustrate the weaknesses of the mainstream approach, and to introduce an alternative approach. Finally, the role of reflective activities in the development of workers’ competence and the relevance of employee participation in workplaces analysis for supporting organizational changing are discussed.In globalized markets, characterized by increasing uncertainty and highly dynamic competition, people have become, a crucial asset in order to support organizational change and competitiveness of companies. The increasing need of flexibility lead firms to the abandonment of “old” HRM systems, seen as too “bureaucratic” and inadequate to manage complex, rapidly evolving markets. Traditional job analysis practices, based on rigid tasks definitions and procedures, were progressively replaced by HR practices based on elements such as workers’ professionalism, creativity, reliability, knowledge, skills; in one word: on people’s competencies. The management of competencies has become a key challenge. Despite the many ambiguities and misunderstandings surrounding the debate on competencies, the development of Competency Based Human Resource System (CBHRS) seem to offer an opportunity to respond quickly and effectively to the current challenges that all kinds of organizations are facing. In this work we analyze and discuss the relationship between the “competency framework” and the issue of organizational change. Our hypothesis is that HR systems, based on the most diffused competency modeling practices, offer limited possibilities, for enacting significant – and not merely rhetorical – organizational changes. Through a literature review of available contributions on the subject, we will explore the key critiques to the mainstream positivist approach. In order to find empirical support to our hypothesis, examples from three case studies will be provided in order to both illustrate the weaknesses of the mainstream approach, and to introduce an alternative approach. Finally, the role of reflective activities in the development of workers’ competence and the relevance of employee participation in workplaces analysis for supporting organizational changing are discussed
Le Corti costituzionali nelle transizioni democratiche: i casi dell’Italia, della Spagna e della Repubblica ceca
No full textThe thesis focuses on the analysis and evaluation of the role of constitutional courts in democratic transitions, with special reference to Italy, Spain and the Czech Republic. The research criticises the “formal” notion of democratic transition, according to which the transition ends with the coming into force of the new Constitution, and argues in favour of a “substantive” notion of democratic transition, i.e. when the principles and values stated in the Constitution are actually put into practice. The reason why the thesis analyses these countries is because each one represents a relevant case study. In fact, the constitutional courts of these countries correspond to three “generations” of European constitutional courts that all emerged from the fall of an authoritarian regime. In the case of Italy, the first “season” of the Constitutional Court was examined. During this period, beginning in 1956 and finishing at the end of the 1960s, the Court focused its activity on eliminating fascist legislation that still limited civil, political, religious and social freedoms. It should be underlined that during the first “generation” of constitutional courts, the role and possible impact of the latter on the constitutional order was still unknown. With regard to the second “generation”, where the Spanish Constitutional Court holds a prominent position, there are less uncertainties and a higher number of experiences that can be imitated, and therefore the birth and the establishment of a system of constitutional justice were facilitated. In the period going from 1980 to the beginning of the Nineties, the Court was very active not only in the interpretation and protection of fundamental rights, but also with regard to the sensitive issue of territorial autonomies. In fact, through its case law, the Court has played a fundamental role in the construction of the “Estado autonomico”. Finally, the Czech Republic represents one the countries that took part in the third “wave of democratisation”, following the fall of the Berlin wall and the implosion of the Soviet Union. During the first ten years of its activity, the Constitutional Court of this country had to decide on many issues concerning so called “transitional justice” and the protection of fundamental rights. Unlike the previous experiences, this case shows the peculiar relationship that the process of democratic transition, the establishment of the constitutional justice and the access to the Council of Europe and the European Union have with one another. The research shows that all democratic transitions have not only basic common feature but also their own peculiar issues, and that constitutional courts play a decisive role in their resolution. The variables influencing the activity of the first years of the constitutional courts, and indirectly the processes of democratisation, are numerous: one just has to think of the model of constitutional justice, the time needed for the constitutional courts to be actually set up, the status and the appointment of constitutional judges, the procedural gateways to constitutional courts and the parties entitled to appeal, the orientation of the other constitutional bodies and of the political actors, the participation of the country to European supranational organisations, the use by the constitutional courts of foreign and comparative law and the reference that they make to the ECHR and the case law of the Court of Strasbourg. This thesis shows that, notwithstanding the specificities of each country, the Constitutional Courts of Italy, Spain and the Czech Republic were leading actors of the processes of “substantive” transition, and they contributed to avoiding “Constitutions without constitutionalism”.The thesis focuses on the analysis and evaluation of the role of constitutional courts in democratic transitions, with special reference to Italy, Spain and the Czech Republic. The research criticises the “formal” notion of democratic transition, according to which the transition ends with the coming into force of the new Constitution, and argues in favour of a “substantive” notion of democratic transition, i.e. when the principles and values stated in the Constitution are actually put into practice. The reason why the thesis analyses these countries is because each one represents a relevant case study. In fact, the constitutional courts of these countries correspond to three “generations” of European constitutional courts that all emerged from the fall of an authoritarian regime. In the case of Italy, the first “season” of the Constitutional Court was examined. During this period, beginning in 1956 and finishing at the end of the 1960s, the Court focused its activity on eliminating fascist legislation that still limited civil, political, religious and social freedoms. It should be underlined that during the first “generation” of constitutional courts, the role and possible impact of the latter on the constitutional order was still unknown. With regard to the second “generation”, where the Spanish Constitutional Court holds a prominent position, there are less uncertainties and a higher number of experiences that can be imitated, and therefore the birth and the establishment of a system of constitutional justice were facilitated. In the period going from 1980 to the beginning of the Nineties, the Court was very active not only in the interpretation and protection of fundamental rights, but also with regard to the sensitive issue of territorial autonomies. In fact, through its case law, the Court has played a fundamental role in the construction of the “Estado autonomico”. Finally, the Czech Republic represents one the countries that took part in the third “wave of democratisation”, following the fall of the Berlin wall and the implosion of the Soviet Union. During the first ten years of its activity, the Constitutional Court of this country had to decide on many issues concerning so called “transitional justice” and the protection of fundamental rights. Unlike the previous experiences, this case shows the peculiar relationship that the process of democratic transition, the establishment of the constitutional justice and the access to the Council of Europe and the European Union have with one another. The research shows that all democratic transitions have not only basic common feature but also their own peculiar issues, and that constitutional courts play a decisive role in their resolution. The variables influencing the activity of the first years of the constitutional courts, and indirectly the processes of democratisation, are numerous: one just has to think of the model of constitutional justice, the time needed for the constitutional courts to be actually set up, the status and the appointment of constitutional judges, the procedural gateways to constitutional courts and the parties entitled to appeal, the orientation of the other constitutional bodies and of the political actors, the participation of the country to European supranational organisations, the use by the constitutional courts of foreign and comparative law and the reference that they make to the ECHR and the case law of the Court of Strasbourg. This thesis shows that, notwithstanding the specificities of each country, the Constitutional Courts of Italy, Spain and the Czech Republic were leading actors of the processes of “substantive” transition, and they contributed to avoiding “Constitutions without constitutionalism”
INTRODUZIONE
No full textQuesta sezione di “I castelli di Yale” ospita cinque riflessioni sul tema, assai poco dibattuto, della decisione artistica direttoriale e dei suoi contenuti. Intenzione degli autori – direttori di teatro o suoi studiosi – è quella di offrire insight in esperienze e idee vive che – quando fossero anche storicizzate – sorreggono però programmi, modelli interpretativi e impegni odierni. Si intende in questo modo portare l’attenzione in particolare sulla necessità di intendere la decisione creativa come capace di agire non attraverso semplici repliche o somiglianze, ma attraverso il concreto tentativo di ricollocare ciò che esiste entro nuove prospettive e scenari.
Il sito CIRSE come risorsa nella ricerca storico-educativa
No full textL’intervento si propone di analizzare l’uso del sito del CIRSE, il “Centro Italiano per la Ricerca Storico Educativa”, quale risorsa per l’informazione nel campo della storia dell’educazione. Nato nel 1980, il CIRSE è un’istituzione, che intende promuovere gli studi e supportare la ricerca accademica nell’ambito della Storia dell’educazione. Il suo archivio contiene una ricca eredità di documenti, incentrati sulla storia di istituti scolastici, sulla storia della didattica e della pratica docente. In questo contributo si prenderanno in esame le trasformazioni avvenute nel Centro stesso e nelle funzioni della sua attività, in ragione dell’influenza delle nuove tecnologie e dei nuovi strumenti di comunicazione.L’intervento si propone di analizzare l’uso del sito del CIRSE, il “Centro Italiano per la Ricerca Storico Educativa”, quale risorsa per l’informazione nel campo della storia dell’educazione. Nato nel 1980, il CIRSE è un’istituzione, che intende promuovere gli studi e supportare la ricerca accademica nell’ambito della Storia dell’educazione. Il suo archivio contiene una ricca eredità di documenti, incentrati sulla storia di istituti scolastici, sulla storia della didattica e della pratica docente. In questo contributo si prenderanno in esame le trasformazioni avvenute nel Centro stesso e nelle funzioni della sua attività, in ragione dell’influenza delle nuove tecnologie e dei nuovi strumenti di comunicazione
Testimonianza
No full textQuesto e l\u27articolo di Giacomo Cives sono due testimonianze, culturali ed amicali al tempo stesso, su Tina Tomasi, a cento anni dalla sua nascitQuesto e l\u27articolo di Giacomo Cives sono due testimonianze, culturali ed amicali al tempo stesso, su Tina Tomasi, a cento anni dalla sua nascita