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Dioxanones (1) are ketal- or acetal protected forms of 1,3-dihydroxyacetone (DHA). The thesis presents the stereoselective aldol transformations of dioxanones and applications to the synthesis of natural and higher carbohydrates listed in Scheme 1.<p> The field of organocatalysis has recently gained much popularity among the chemical research community. In our group, a set of conditions are developed to perform stereoselective aldol reactions on dioxanone substrate. Cs-symmetrical dioxanones have superior diasteroselectivities than C2v-symmetrical dioxanones (de up to 88% from 34%) and presence of mild Lewis acid (LiCl) or Brønsted acid additives (PyPTS) enhance the enantioselectivity into synthetically useful ranges (from 60 up to 96 % ee).<p> The first aldol addition of dioxanone (1) to desired aldehydes (possessing masked carbonyl functionality), followed by reduction of the corresponding aldol adduct and upon unmasking the aldehyde functionality (i.e dithiane or dimethoxy acetal hydrolysis) resulted in furanose (II) and pyranose (III) forms of D-ribose.<p> A new protocol was developed for the synthesis of biologically important deoxyiminosugars such as L-1-deoxymannojirimycin (DMJ, IV), L-1-deoxyidonojirimycin (DIJ, V) and N-isopropyl DIJ (IV) from readily available dioxanone (1) precursor. The key steps include diastereoselective proline-catalyzed syn-aldol transformation and a reductive amination / cyclization.<p> D-glycero-D-manno-2-octulose (VII), a higher-carbon sugar isolated from opium poppies has been synthesized in enantiomerically pure form. The short synthetic sequence involved two proline-catalyzed aldol addition reactions of dioxanone (1) to appropriate aldehydes. Here, we developed a complete dioxanone methodology towards the higher monosaccharide in a stereocontrolled fashion.<p> The enantioselective stereodivergent first total synthesis of DD- and LL-glycero-β-alloheptopyranose (IX, ent-IX) was accomplished from readily available non-chiral starting materials. The short synthetic sequence involves enamine and enolate mediated aldol reactions at α and α' positions of dioxanone (1) hence demonstrated the complementary nature of organocatalysis and organometallic methods.

Dioxanones (1) are ketal- or acetal protected forms of 1,3-dihydroxyacetone (DHA). The thesis presents the stereoselective aldol transformations of dioxanones and applications to the synthesis of natural and higher carbohydrates listed in Scheme 1.<p> The field of organocatalysis has recently gained much popularity among the chemical research community. In our group, a set of conditions are developed to perform stereoselective aldol reactions on dioxanone substrate. Cs-symmetrical dioxanones have superior diasteroselectivities than C2v-symmetrical dioxanones (de up to 88% from 34%) and presence of mild Lewis acid (LiCl) or Brønsted acid additives (PyPTS) enhance the enantioselectivity into synthetically useful ranges (from 60 up to 96 % ee).<p> The first aldol addition of dioxanone (1) to desired aldehydes (possessing masked carbonyl functionality), followed by reduction of the corresponding aldol adduct and upon unmasking the aldehyde functionality (i.e dithiane or dimethoxy acetal hydrolysis) resulted in furanose (II) and pyranose (III) forms of D-ribose.<p> A new protocol was developed for the synthesis of biologically important deoxyiminosugars such as L-1-deoxymannojirimycin (DMJ, IV), L-1-deoxyidonojirimycin (DIJ, V) and N-isopropyl DIJ (IV) from readily available dioxanone (1) precursor. The key steps include diastereoselective proline-catalyzed syn-aldol transformation and a reductive amination / cyclization.<p> D-glycero-D-manno-2-octulose (VII), a higher-carbon sugar isolated from opium poppies has been synthesized in enantiomerically pure form. The short synthetic sequence involved two proline-catalyzed aldol addition reactions of dioxanone (1) to appropriate aldehydes. Here, we developed a complete dioxanone methodology towards the higher monosaccharide in a stereocontrolled fashion.<p> The enantioselective stereodivergent first total synthesis of DD- and LL-glycero-β-alloheptopyranose (IX, ent-IX) was accomplished from readily available non-chiral starting materials. The short synthetic sequence involves enamine and enolate mediated aldol reactions at α and α' positions of dioxanone (1) hence demonstrated the complementary nature of organocatalysis and organometallic methods.

A new class of oxazolidinone chiral auxiliary has been synthesized from various α-amino acids, incorporating a perfluoroalkyl functional chain as a soluble support. This feature allows the chiral auxiliaries to be employed under standard solution-phase reaction conditions, and rapidly purified from crude mixtures using fluorous solid phase extraction (FSPE). Our investigation of these new materials has been divided into two main sections. To obtain the chiral auxiliaries in multi-gram quantities a synthetic protocol was designed, where efficiency and reproducibility were the primary objectives. Meeting these goals required an extensive study of the reactivity of perfluoroalkyl nucleophiles. This study identified a versatile and scalable protocol for the perfluoroalkylation of the required amino acid starting materials. These results have allowed us to design a general, five-step synthetic pathway to create the fluorous chiral auxiliaries quickly and effectively. The new auxiliaries were then applied in several model reactions, specifically chosen to examine the reactivity and behavior of these compounds. In particular, the auxiliaries were tested for their stereoselectivity, recyclability, and ease of purification, in a series of Aldol reactions, 1,3 dipolar cycloadditions, and radical conjugate additions. This set of model reactions, combined with the facile and efficient synthesis clearly demonstrates that these new chiral auxiliaries are useful alternatives to the non-fluorous oxazolidinone chiral auxiliaries currently employed in stoichiometric asymmetric syntheses. / February 2006

A new class of oxazolidinone chiral auxiliary has been synthesized from various α-amino acids, incorporating a perfluoroalkyl functional chain as a soluble support. This feature allows the chiral auxiliaries to be employed under standard solution-phase reaction conditions, and rapidly purified from crude mixtures using fluorous solid phase extraction (FSPE). Our investigation of these new materials has been divided into two main sections. To obtain the chiral auxiliaries in multi-gram quantities a synthetic protocol was designed, where efficiency and reproducibility were the primary objectives. Meeting these goals required an extensive study of the reactivity of perfluoroalkyl nucleophiles. This study identified a versatile and scalable protocol for the perfluoroalkylation of the required amino acid starting materials. These results have allowed us to design a general, five-step synthetic pathway to create the fluorous chiral auxiliaries quickly and effectively. The new auxiliaries were then applied in several model reactions, specifically chosen to examine the reactivity and behavior of these compounds. In particular, the auxiliaries were tested for their stereoselectivity, recyclability, and ease of purification, in a series of Aldol reactions, 1,3 dipolar cycloadditions, and radical conjugate additions. This set of model reactions, combined with the facile and efficient synthesis clearly demonstrates that these new chiral auxiliaries are useful alternatives to the non-fluorous oxazolidinone chiral auxiliaries currently employed in stoichiometric asymmetric syntheses.

A new class of oxazolidinone chiral auxiliary has been synthesized from various α-amino acids, incorporating a perfluoroalkyl functional chain as a soluble support. This feature allows the chiral auxiliaries to be employed under standard solution-phase reaction conditions, and rapidly purified from crude mixtures using fluorous solid phase extraction (FSPE). Our investigation of these new materials has been divided into two main sections. To obtain the chiral auxiliaries in multi-gram quantities a synthetic protocol was designed, where efficiency and reproducibility were the primary objectives. Meeting these goals required an extensive study of the reactivity of perfluoroalkyl nucleophiles. This study identified a versatile and scalable protocol for the perfluoroalkylation of the required amino acid starting materials. These results have allowed us to design a general, five-step synthetic pathway to create the fluorous chiral auxiliaries quickly and effectively. The new auxiliaries were then applied in several model reactions, specifically chosen to examine the reactivity and behavior of these compounds. In particular, the auxiliaries were tested for their stereoselectivity, recyclability, and ease of purification, in a series of Aldol reactions, 1,3 dipolar cycloadditions, and radical conjugate additions. This set of model reactions, combined with the facile and efficient synthesis clearly demonstrates that these new chiral auxiliaries are useful alternatives to the non-fluorous oxazolidinone chiral auxiliaries currently employed in stoichiometric asymmetric syntheses.

Aldol reactions are widely used in forming new carbon-carbon bonds. Since the discovery of the aldol condensation, controlling the relative and absolute stereochemistry in aldol chemistry has been a major interest in organic chemistry. Efforts in achieving diastereoselectivity in aldol reactions via chelation of Lewis acids to chiral aldehydes are reviewed. The following chapters discuss the diastereoselectivities of hydrogen-mediated reductive aldol reactions. Herein, a highly diastereoselective reductive aldol coupling reactions with broad substrate scope using rhodium catalysts ligated to (2-furyl)₃P were studied. It was demonstrated that the coupling of enones with alpha-amino aldehydes proceeds with high diastereoselectivity via chelation control. The second topic deals with phosphine-mediated furan ring formation. Derivatives of furan are often found in natural products and therapeutic agents. To provide a more facile route to substituted furans, we have developed a phosphine mediated reductive cyclization of gamma-acyloxy butynoates. In this reaction, phosphine is involved in both the reductive formation of allenyl ketones from acyloxy butynoates and the subsequent catalytic cyclization. / text

Orientador: Luiz Carlos Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T09:34:22Z (GMT). No. of bitstreams: 1 Oliveira_VandaMariade_M.pdf: 2580285 bytes, checksum: 691d41628333efc92e279be76c7dd14c (MD5) Previous issue date: 2008 / Resumo: O capítulo 1 descreve as reações aldólicas de enolatos de boro de metilcetonas quirais com aldeídos aquirais. Neste trabalho relatamos resultados que sugerem a competição entre a estereoindução 1,4/1,5 na construção da ligação C-C dos adutos de aldol. Os produtos foram obtidos com seletividades que variam de 50:50 a 70:30, e em rendimentos que variaram de 82-95%. O capitulo 2 descreve as reações aldólicas de enolatos de boro de metilcetonas com a-aminoaldeidos para a síntese estereosseletiva de 3-hidroxi-4-aminocetonas. Estas reações forneceram os adutos de aldol com estereoquímica relativa 1,2-syn, com estereosseletividades na faixa de 66:33 a >95:05 e rendimentos que variaram de 30-92% / Abstract: The chapter 1 describes the boron-mediated aldol reactions of a-methyl-b-alkoxy methylketones with achiral aldehydes. The results described here suggest a possible competition between 1,4 and 1,5 stereoindution in the construction of C-C bonds. These reactions gave the corresponding aldol adducts with selectivities ranging from 50:50 to 70:30 in good yields (82.95%). The Chapter 2 describes the aldol reaction of boron enolates generated from methylketones with chiral a-amino aldehydes for the stereoselective synthesis of 4-N-Boc-amino-3-hydroxy ketones. These reactions gave the 1,2.syn aldol aducts with diastereoselectivities ranging from 66:33 to 95:05 in good overallyields (30-92%) / Mestrado / Quimica Organica / Mestre em Química

Nesta tese foram feitos estudos cujo objetivo principal foi centrado na síntese, caracterização e estudos da morfologia e das aplicações de polímeros helicoidais fenilacetilênicos contendo grupos laterais opticamente ativos. O trabalho foi dividido em 3 capítulos. O primeiro consistiu do estudo de inserção da fração acetilênica em núcleos aril- e piridil-oxazolínicos. Algumas limitações experimentais foram observadas em função da funcionalização das porções monoméricas sob as condições de polimerização. O segundo estudo consistiu do controle de crescimento das cadeias poliméricas, por ação de nanopartículas tipo core-shell (Au@Te-NP\'s). Foi observado que sob tais condições obtém-se cadeias poliméricas substancialmente menores do que na ausência dessas partículas. O terceiro capítulo consistiu no uso de polímeros helicoidais derivados de prolina para catálise assimétrica de reações do tipo aldol. Os resultados se mostraram promissores. Esses estudos não foram concluídos mas foi possível obter produtos com altos excessos enantio- e diastereoisomericos. / This thesis aimed the synthesis, characterization, morphology studies and applications of phenylacetilenic helical polymers containing optically active pendant groups. The results are presented in three chapters. The first was centered on the functionalization of aril- and pyridil-oxazolines with the acetylenic portion. Some experimental limitations were faced because of the functionalization of the monomers under polymerization conditions. The second chapter was dedicated to the utilization of core-shell nanoparticles (Au@Te-NP\'s) on the control of polymer chain growth. The presence of these NPs ensures the production of substantially smaller polymeric chains. The third chapter was dedicated to the employment of the optically active helical polymers as catalysts for aldol type reactions. These studies couldn\'t be concluded but where very promissory leading to products with high enantio- and diastereomeric excess.

Nesta tese foram feitos estudos cujo objetivo principal foi centrado na síntese, caracterização e estudos da morfologia e das aplicações de polímeros helicoidais fenilacetilênicos contendo grupos laterais opticamente ativos. O trabalho foi dividido em 3 capítulos. O primeiro consistiu do estudo de inserção da fração acetilênica em núcleos aril- e piridil-oxazolínicos. Algumas limitações experimentais foram observadas em função da funcionalização das porções monoméricas sob as condições de polimerização. O segundo estudo consistiu do controle de crescimento das cadeias poliméricas, por ação de nanopartículas tipo core-shell (Au@Te-NP\'s). Foi observado que sob tais condições obtém-se cadeias poliméricas substancialmente menores do que na ausência dessas partículas. O terceiro capítulo consistiu no uso de polímeros helicoidais derivados de prolina para catálise assimétrica de reações do tipo aldol. Os resultados se mostraram promissores. Esses estudos não foram concluídos mas foi possível obter produtos com altos excessos enantio- e diastereoisomericos. / This thesis aimed the synthesis, characterization, morphology studies and applications of phenylacetilenic helical polymers containing optically active pendant groups. The results are presented in three chapters. The first was centered on the functionalization of aril- and pyridil-oxazolines with the acetylenic portion. Some experimental limitations were faced because of the functionalization of the monomers under polymerization conditions. The second chapter was dedicated to the utilization of core-shell nanoparticles (Au@Te-NP\'s) on the control of polymer chain growth. The presence of these NPs ensures the production of substantially smaller polymeric chains. The third chapter was dedicated to the employment of the optically active helical polymers as catalysts for aldol type reactions. These studies couldn\'t be concluded but where very promissory leading to products with high enantio- and diastereomeric excess.