A presente tese de doutorado descreve a integração de metodologias sintéticas da química de organoteluretos desenvolvidas nos últimos anos pelo grupo. Especialmente a hidroteluração de cetonas α,β-insaturadas, a resolução cinética enzimática de hidróxi-teluretos e a reação de troca Te/Li. Tais metodologias, empregadas em sequência, possibilitaram a obtenção de blocos sintéticos versáteis na preparação de reagentes organometálicos funcionalizados e enantiomericamente enriquecidos. Esse protocolo mostrou-se eficiente na preparação de uma variedade de produtos naturais, como por exemplo, feromônios de insetos-praga e butirolactonas com atividades biológicas relevantes. O trabalho foi dividido em duas partes. Estudou-se a reatividade e o emprego de organoteluretos alquílicos (sp3) e vinílicos (sp2) O-funcionalizados, na síntese dos produtos naturais citados acima. Na primeira parte do trabalho estudou-se a utilização de organoteluretos vinílicos. Esta classe de compostos foi preparada a partir da hidroteluração de alquinonas, os intermediários carbonílicos foram reduzidos com NaBH4, fornecendo uma mistura racêmica de hidróxi-teluretos vinílicos. Esses compostos foram submetidos à resolução cinética enzimática, empregando a lipase, disponível comercialmente, Novozyme® 435. Os resultados, quanto à excessos enantioméricos e rendimentos foram bons, possibilitando a obtenção de hidróxi-teluretos vinílicos enantiomericamente enriquecidos em até 96% e.e. Na etapa seguinte, efetuou-se a reação de troca Te/Li, gerando um reagente organometálico funcionalizado, denominado 1,4-(C,O) diânion vinílico de lítio. Pela eletronegatividade do átomo de lítio possibilitar vários tipos de transmetalações, esse intermediário é de grande valia em síntese orgânica. Na presença de eletrófilos, como CO2, esse diânion apresentou boa reatividade, gerando α-alquil-γ-butenolidas, após hidrólise em meio ácido. Tais butenolidas, constituíram-se como esqueleto avançado na síntese da (+)-Blastimicinona, (-)-Blastimicinolactol, (+)-Antimicinona, (-)-NFX-2 e todos os isômeros da Acaterina, em bons rendimentos globais. Esses compostos apresentam atividades antifúngicas, antitumorais e inibitórias de enzimas relacionadas à Arteriosclerose, respectivamente. Na segunda parte do trabalho estudou-se a utilização de um organotelureto alquílico em particular. Obtido a partir da hidroteluração da metil-vinil-cetona e redução in situ, do intermediário carbonílico. A mistura racêmica obtida foi resolvida através de resolução cinética enzimática, empregando a lipase, disponível comercialmente, Novozyme® 435. Os resultados, quanto a excessos enantioméricos e rendimentos foram bons, possibilitando a obtenção dos dois enantiômeros do respectivo hidróxi-telureto alquílico em excessos enantioméricos de até 99%. Na etapa seguinte, efetuou-se a reação de troca Te/Li, gerando um reagente organometálico funcionalizado, denominado 1,4-(C,O) diânion alquílico de lítio que foi transmetalado para uma série organocupratos. Ao reagi-lo com tosilatos específicos e realizar work-up com Ac2O, obteve-se uma série de feromônios de insetos-praga (C. pisi, M. destructor e D. mulleri) em bons rendimentos. / This PhD thesis describes the integration of synthetic methodologies involving organotellurides chemistry developed in recent years by the group, especially hydrotelluration of α,β-unsaturated ketones, enzymatic kinetic resolution of hydroxytellurides and Te/Li exchange reaction. These methods, used together, made it possible to obtain versatile synthetic blocks which were used in the preparation of functionalized and enantiomerically enriched organometallic reagents, featuring a synthetic key step in preparing a variety of natural products, such as Insect Pheromones and Butyrolactones with relevant biological activities. This work was divided into two parts. We studied the reactivity and the application of alkyl (sp3) and vinyl (sp2) O-functionalized organotellurides, in the synthesis of natural products cited above. In the first part of the work we studied the use of vinyl organotellurides. This class of compounds was prepared from hydrotelluration of alkynones, carbonyl intermediates were reduced with NaBH4 giving a racemic mixture of hydroxy-vinyl tellurides. These compounds were subjected to enzymatic kinetic resolution, using the lipase NovozymeTM 435. The results, as the yields and enantiomeric excesses were good yielding hydroxy-vinylic tellurides with enantiomeric excesses up to 96%. In the next step we performed the Te/Li exchange reaction, generating a functionalized organometallic reagent, known as lithium 1,4-(C,O) vinyl dianion. According to the characteristics of the electronegative atom of lithium, this intermediate is of great value in organic synthesis. In the presence of electrophiles such as CO2 showed good reactivity generating α-alkyl-γ-butenolides after acid hydrolysis. Such Butyrolactones constituted themselves as a skeleton for the synthesis of advanced (+)-Blastmycinone, (-)-Blastmycinolactol, (+)-Antimycinone, (-)-NFX-2 and all isomers of Acaterin in good overall yields. These compounds have antifungal and antitumor activity and inhibitory enzymes related to arteriosclerosis, respectively. In the second part of the work we studied the use of a specific alkyl organotelluride obtained by hydrotelluration of methyl vinyl ketone and in situ reduction of carbonyl intermediate by NaBH4. The racemic mixture was submitted to enzymatic kinetic resolution using the lipase NovozymeTM 435. The results, as the yields and enantiomeric excesses were good, allowing to obtain the two enantiomers of the corresponding hydroxy-alkyl telluride with enantiomeric excess of up to 99%. In the next step we performed the Te/Li exchange reaction, generating a functionalized organometallic reagent, known as lithium 1,4- (C,O) alkyl dianion that was used for the transmetallation for several organocuprate which when reacted with tosylates and perform specific work-up provided a number of pheromones of pest insects (C. pisi, M. destructor and D. mulleri) in good yields.

A presente tese de doutorado descreve a integração de metodologias sintéticas da química de organoteluretos desenvolvidas nos últimos anos pelo grupo. Especialmente a hidroteluração de cetonas α,β-insaturadas, a resolução cinética enzimática de hidróxi-teluretos e a reação de troca Te/Li. Tais metodologias, empregadas em sequência, possibilitaram a obtenção de blocos sintéticos versáteis na preparação de reagentes organometálicos funcionalizados e enantiomericamente enriquecidos. Esse protocolo mostrou-se eficiente na preparação de uma variedade de produtos naturais, como por exemplo, feromônios de insetos-praga e butirolactonas com atividades biológicas relevantes. O trabalho foi dividido em duas partes. Estudou-se a reatividade e o emprego de organoteluretos alquílicos (sp3) e vinílicos (sp2) O-funcionalizados, na síntese dos produtos naturais citados acima. Na primeira parte do trabalho estudou-se a utilização de organoteluretos vinílicos. Esta classe de compostos foi preparada a partir da hidroteluração de alquinonas, os intermediários carbonílicos foram reduzidos com NaBH4, fornecendo uma mistura racêmica de hidróxi-teluretos vinílicos. Esses compostos foram submetidos à resolução cinética enzimática, empregando a lipase, disponível comercialmente, Novozyme® 435. Os resultados, quanto à excessos enantioméricos e rendimentos foram bons, possibilitando a obtenção de hidróxi-teluretos vinílicos enantiomericamente enriquecidos em até 96% e.e. Na etapa seguinte, efetuou-se a reação de troca Te/Li, gerando um reagente organometálico funcionalizado, denominado 1,4-(C,O) diânion vinílico de lítio. Pela eletronegatividade do átomo de lítio possibilitar vários tipos de transmetalações, esse intermediário é de grande valia em síntese orgânica. Na presença de eletrófilos, como CO2, esse diânion apresentou boa reatividade, gerando α-alquil-γ-butenolidas, após hidrólise em meio ácido. Tais butenolidas, constituíram-se como esqueleto avançado na síntese da (+)-Blastimicinona, (-)-Blastimicinolactol, (+)-Antimicinona, (-)-NFX-2 e todos os isômeros da Acaterina, em bons rendimentos globais. Esses compostos apresentam atividades antifúngicas, antitumorais e inibitórias de enzimas relacionadas à Arteriosclerose, respectivamente. Na segunda parte do trabalho estudou-se a utilização de um organotelureto alquílico em particular. Obtido a partir da hidroteluração da metil-vinil-cetona e redução in situ, do intermediário carbonílico. A mistura racêmica obtida foi resolvida através de resolução cinética enzimática, empregando a lipase, disponível comercialmente, Novozyme® 435. Os resultados, quanto a excessos enantioméricos e rendimentos foram bons, possibilitando a obtenção dos dois enantiômeros do respectivo hidróxi-telureto alquílico em excessos enantioméricos de até 99%. Na etapa seguinte, efetuou-se a reação de troca Te/Li, gerando um reagente organometálico funcionalizado, denominado 1,4-(C,O) diânion alquílico de lítio que foi transmetalado para uma série organocupratos. Ao reagi-lo com tosilatos específicos e realizar work-up com Ac2O, obteve-se uma série de feromônios de insetos-praga (C. pisi, M. destructor e D. mulleri) em bons rendimentos. / This PhD thesis describes the integration of synthetic methodologies involving organotellurides chemistry developed in recent years by the group, especially hydrotelluration of α,β-unsaturated ketones, enzymatic kinetic resolution of hydroxytellurides and Te/Li exchange reaction. These methods, used together, made it possible to obtain versatile synthetic blocks which were used in the preparation of functionalized and enantiomerically enriched organometallic reagents, featuring a synthetic key step in preparing a variety of natural products, such as Insect Pheromones and Butyrolactones with relevant biological activities. This work was divided into two parts. We studied the reactivity and the application of alkyl (sp3) and vinyl (sp2) O-functionalized organotellurides, in the synthesis of natural products cited above. In the first part of the work we studied the use of vinyl organotellurides. This class of compounds was prepared from hydrotelluration of alkynones, carbonyl intermediates were reduced with NaBH4 giving a racemic mixture of hydroxy-vinyl tellurides. These compounds were subjected to enzymatic kinetic resolution, using the lipase NovozymeTM 435. The results, as the yields and enantiomeric excesses were good yielding hydroxy-vinylic tellurides with enantiomeric excesses up to 96%. In the next step we performed the Te/Li exchange reaction, generating a functionalized organometallic reagent, known as lithium 1,4-(C,O) vinyl dianion. According to the characteristics of the electronegative atom of lithium, this intermediate is of great value in organic synthesis. In the presence of electrophiles such as CO2 showed good reactivity generating α-alkyl-γ-butenolides after acid hydrolysis. Such Butyrolactones constituted themselves as a skeleton for the synthesis of advanced (+)-Blastmycinone, (-)-Blastmycinolactol, (+)-Antimycinone, (-)-NFX-2 and all isomers of Acaterin in good overall yields. These compounds have antifungal and antitumor activity and inhibitory enzymes related to arteriosclerosis, respectively. In the second part of the work we studied the use of a specific alkyl organotelluride obtained by hydrotelluration of methyl vinyl ketone and in situ reduction of carbonyl intermediate by NaBH4. The racemic mixture was submitted to enzymatic kinetic resolution using the lipase NovozymeTM 435. The results, as the yields and enantiomeric excesses were good, allowing to obtain the two enantiomers of the corresponding hydroxy-alkyl telluride with enantiomeric excess of up to 99%. In the next step we performed the Te/Li exchange reaction, generating a functionalized organometallic reagent, known as lithium 1,4- (C,O) alkyl dianion that was used for the transmetallation for several organocuprate which when reacted with tosylates and perform specific work-up provided a number of pheromones of pest insects (C. pisi, M. destructor and D. mulleri) in good yields.

A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehyde. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

The thesis entitled ‘Studies of NIS Mediated Cyclopropane Ring Opening Reactions in Carbohydrate Chemistry’ is divided into four chapters. Chapter 1: Section 1: Efficient Synthesis of Fused Perhydrofuro[2,3-b]pyrans (and furans) by Ring Opening of 1,2-Cyclopropanated Sugar Derivatives. In this section a general and efficient methodology for the synthesis of carbohydrate derived perhydrofuro[2,3-b]pyrans (and furans) from the corresponding 1,2-cyclopropane carboxylates has been discussed. A wide range of linear-fused perhydrofuro[2,3-b]pyran or furan ring systems are encountered in a number of biologically active natural products. A few approaches are available for the construction of this kind of fused motifs which involve harsh reaction conditions and lengthy reaction sequence. The methodology utilizes the potential ability of cyclopropanated sugars to undergo N-iodosuccinimide (NIS) mediated electrophilic ring opening assisted by the pyran ring oxygen followed by intramolecular trapping of oxonium intermediate to generate the furan ring system. Cyclopropantion of tribenzyl glucal using methyl diazoacetate and catalytic amount of dirhodiumtetracetate furnished corresponding exo-1,2-cyclopropane carboxylate exclusively. To generate a nucleophile, cyclopropane carboxylate ester was reduced to the corresponding alcohol which upon treatment with NIS in CH3CN underwent ring opening followed by intramolecular ring closure to give the corresponding perhydro[2,3-b]furopyran along with an oxidized product. After various modifications we found that using CH2Cl2 as a solvent gave the expected perhydrofuropyran as the sole product in good yield (Scheme I). The stereochemistry of the product was established on the basis of 1H-1H NOESY experiment. There are many natural products that contain the perhydrofuro[2,3-b]furyl glycal core such as clerodin, jodrelline B and caryoptin, which show insect anti-feedant properties. With this in mind, the methodology has been successfully extended to the cyclopropanated tetrahydrofuran derivatives resulting in the synthesis of furofuryl glycal moiety (Scheme II). Scheme II Chapter 1: Section 2: Synthesis of Carbohydrate Derived Fused Perhydrofuro/pyrano[2,3-b]-γ-butyrolactones. In this section a general and efficient methodology for the synthesis of carbohydrate derived perhydrofuro/pyrano[2,3-b]-γ-butyrolactones has been discussed. The fusion of the γ-butyrolactone onto a substituted tetrahydrofuran/pyran ring makes a distinctive class natural diterpenoids. Representative members of this family include the marine diterpenoids norrisilide and miniolutelide A. In this chapter we describe a neutral and general method for the construction of perhydrofuro/pyrano[2,3-b]-γ-butyrolactones by NIS mediated ring opening of carbohydrate derived 1,2-cyclopropane carboxylic acids (Scheme III). Scheme III The present strategy is complementary to the existing methods and it is useful since it incorporates an additional chiral center in the molecule under milder conditions, which can be used for further transformations. Chapter 2: Ring Opening of Activated Cyclopropanes with NIS/NaN3: One-pot Synthesis of C-1 Linked Pseudo Disaccharides. Ring opening reactions of activated cyclopropanes have been widely used in organic synthesis. But they are restricted to only selected nucleophiles such as alcohol/ water, as most of the ring opening reactions need acidic activation. This chapter deals with studies of reactivity of various activated cyclopropanes with NIS as a neutral activator and sodium azide as a source of nitrogen nucleophile (Scheme IV). Scheme IV We have clearly demonstrated not only the importance of the donor-acceptor feature in the cyclopropanes in the electrophilic ring opening reaction, but also the selectivity in its functionality. Scheme V This methodology has been successfully utilized in a one-pot synthesis of C-1 linked pseudo-disaccharides from carbohydrate derived 1,2-cyclopropane carboxylates (Scheme V). Chapter 3: Synthesis of Unnatural C-2 Amino Acid Nucleosides Using NIS Mediated Ring Opening of 1,2-Cyclopropane Carboxylated Sugar Derivatives. In this chapter, we have efficiently demonstrated the utility of NIS mediated regioselective ring opening of carbohydrate derived donor-acceptor cyclopropanes for the synthesis of C-2 amino acid nucleosides. This leads to a new class of analogs of peptidyl nucleosides (Scheme VI). Scheme VI One of the advantageous factors is the attachment of nucleobase as well as generation of amino acid precursor in the same reaction which avoids lengthy reaction sequence. We have also shown the synthetic utility of our methodology to pyrimidine based furanosyl C-2 amino acid nucleosides which are of interest, since polyoxins having similar structural core exhibit antifungal activity (Scheme VII). Chapter 4: Attempts Towards the Synthesis of Carbohydrate Derived Spiro-perhydrofuropyrans Using NIS Mediated Cyclopropane Ring Opening Reaction. In this chapter we present various attempts to synthesize spiro-perhydrofuropyran/furans by ring opening of spiro-cylopropane derivatives and attempts towards stereoselective synthesis of spiro-cyclopropane carboxylates. Spiroacetal can be synthesized from the corresponding exo-cyclopropyl methanol, which can be obtained from the corresponding exo- cyclopropane carboxylate. The cyclopropyl carboxylate can be obtained from an exo- vinyl ether. Cyclopropanation of carbohydrate derived exo-glycal failed to give any selectivity under a variety of reaction conditions (Scheme VIII). Carbohydrate derived C1-unsaturated ester on cyclopropanation reaction using standard conditions (Pd(OAc)2/CH2N2) was found to be inert. The reaction under Simmons-Smith cyclopropanation conditions also gave similar results. Reduction of the ester part of the molecule to the corresponding alcohol was found to be helpful in the Simmon-Smith cyclopropanation reaction (CH2I2, Et2Zn) to obtain the corresponding exo-cyclopropane, but disappointingly without any selectivity (Scheme IX). In order to get exo-cyclopropane carboxylate with high stereoselectivity, we decided to use one of the hydroxyl group present in the molecule, as a chiral auxiliary. All the established methods for the diazoester formation failed to attach diazo ester at C-4 position (Scheme X). Scheme X (For structural formula pl see the pdf file)

A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehyde. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.