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Papers by maria eduarda salles silva
Carbohydrate Polymers, 2015
6-O-methacryloyl-α-d-glucoside 2 and 4-bromophenyl-6-O-methacryloyl-d-glucothioside 7, obtained b... more 6-O-methacryloyl-α-d-glucoside 2 and 4-bromophenyl-6-O-methacryloyl-d-glucothioside 7, obtained by enzyme-catalyzed synthesis, have been homo-polymerized and copolymerized with styrene by a free radical process, yielding polymer materials with sugar moieties, attached to the polymer backbone via ester linkages. The results demonstrated that modifying the structural features of the monomers greatly affected the thermal and rheological properties of the polymers. The polymer materials obtained have been characterized by NMR, MALDI-MS, DSC, AFM, and EWC (equilibrium water content). The AFM images indicated the formation of spherical and core-shell polymeric microparticles.
Carbohydrate Research, 2014
The ubiquity of glycoconjugates in nature and their role in different biological processes, has l... more The ubiquity of glycoconjugates in nature and their role in different biological processes, has led to the development of several methodologies to synthesize these molecules. Synthetic glycoconjugates are now used to answer a variety of glycoconjugate-related biological questions and has provided new potential vaccines against cancer, viral and bacterial infections and new biotechnological tools. This review aims to collect and compile the recent advances in the field of glycopeptides, glycoproteins and glycolipid synthesis and also to update the previous reviews made on this subject. Finally, by highlighting the successes and failures of past research, we hope that this review will inspire fruitful research in this important medicinal chemistry field.
Tetrahedron, 2009
A short synthesis of the natural potent cytotoxic agent (−)-muricatacin 1 and related unsaturated... more A short synthesis of the natural potent cytotoxic agent (−)-muricatacin 1 and related unsaturated lactones from a versatile common intermediate, dienedioate 2, derived from d-mannitol or tartaric acid, is described. The strategy depends upon the desymmetrization of 7 by dihydroxylation and elaboration of the hydroxy alkyl sidechain. A route to unsaturated lactones is also described using a cis selective Wittig
Tetrahedron: Asymmetry, 2005
ABSTRACT Novel chiral C2-symmetric bis(oxazolines) were prepared from tartaric acid. They were ap... more ABSTRACT Novel chiral C2-symmetric bis(oxazolines) were prepared from tartaric acid. They were applied as ligands in the copper-catalyzed conjugate addition of diethylzinc to chalcone and 2-cyclohexenone. Maximum enantiomeric excesses of 50% and 53% were obtained, respectively. The sense of induction was found to depend on the configuration of the stereogenic centre in the oxazoline ring, and not on the stereogenic centres of the 1,4-dioxane backbone.
The Journal of Physical Chemistry A, 2008
The thermal decomposition of azidoacetone (CH 3 COCH 2 N 3) was studied using a combined experime... more The thermal decomposition of azidoacetone (CH 3 COCH 2 N 3) was studied using a combined experimental and computational approach. Flash pyrolysis at a range of temperatures (296-1250 K) was used to induce thermal decomposition, and the resulting products were expanded into a molecular beam and subsequently analyzed using electron bombardment ionization coupled to a quadrupole mass spectrometer. The advantages of this technique are that the parent molecules spend a very short time in the pyrolysis zone (20-30 µs) and that the subsequent expansion permits the stabilization of thermal products that are not observable using conventional pyrolysis methods. A detailed analysis of the mass spectra as a function of pyrolysis temperature revealed the participation of five thermal decomposition channels. Ab initio calculations on the stable structures and transition states of the azidoacetone system in combination with an analysis of the dissociative ionization pattern of each channel allowed the identity and mechanism of each channel to be elucidated. At low temperatures (296-800 K) the azide decomposes principally by the loss of N 2 to yield the imine (CH 3 COCHNH), which can further decompose to CH 3 CO and CHNH. At low and intermediate temperatures a process involving the loss of N 2 to yield CH 3 CHO and HCN is also open. Finally, at high temperatures (800-1250 K) a channel in which the azide decomposes to a stable cyclic amine (CO(CH 2) 2 NH) (after loss of N 2) is active. The last channel involves subsequent thermal decomposition of this cyclic amine to ketene (H 2 CCO) and methanimine (H 2 CNH).
Tetrahedron Letters, 1999
An asymmetric synthesis of (+)-epibatidine is described which uses the increased stereoselectivit... more An asymmetric synthesis of (+)-epibatidine is described which uses the increased stereoselectivity of a borohydride reduction induced by the presence of DMSO.
Tetrahedron Letters, 1993
A cyclopentane derivative elaborated from (-)-quinic acid has been converted efficiently and ster... more A cyclopentane derivative elaborated from (-)-quinic acid has been converted efficiently and stereoselectively into several cyclopentylamines, precursors to c'arhocyclic nucleosldes which have previously been shown to be biologzally mterestmg Recent reviews' on the subject of nucleoside synthesis and their activity as agents in the fight against the HIV and other viruses have highhghted the Importance of their carbocyclic analogues as possible treatments for AIDS. Carbovir 3 (B=guanine)1*2 has been the target of several research groups because of its high antiviral activity. Other polysubstituted
Tetrahedron Letters, 1994
Absfruct: Quinic acid is converted stereoselectively into a common cyclopentane intennediatc usef... more Absfruct: Quinic acid is converted stereoselectively into a common cyclopentane intennediatc useful for the synthesis of carbocyclii nucleoskks prostagkmdii and other importaut cyclopentane based compunds.
Tetrahedron Letters, 1989
Tetrahedron Letters, 1995
During studies related to the elaboration of prostaglandin precursors we have reduced the ketonic... more During studies related to the elaboration of prostaglandin precursors we have reduced the ketonic carbonyl group of a number of optically active 2-substituted-4-hydroxy-2-cyclopentenone esters and ethers using sodium borohydride and cerium trichloride under various conditions. High diastereoselectivity is achieved only with some 4-substituents.
Tetrahedron Letters, 1999
The novel chiral bis-acetal dioxane 2a derived from (2R,3R)-(+)-tartaric acid was shown to underg... more The novel chiral bis-acetal dioxane 2a derived from (2R,3R)-(+)-tartaric acid was shown to undergo an unexpected rearrangement upon treatment with lithium amide base to give the chiral dioxolane 3a in optically active form. Alkylation and aldol studies were performed on the diisopropyl ester of this dioxolane 3b.
Tetrahedron Letters, 1997
The sulphoxidation of the enol ethers of some acyldithiolanes using the Sharpless epoxidation rea... more The sulphoxidation of the enol ethers of some acyldithiolanes using the Sharpless epoxidation reagents followed by fluorolysis results in better overall stereoselectivity than direct oxidation of the acyldithiolane thus providing a highly stereoselective route to acyldithiolane sulphoxides. Fluorolysis under acid conditions of non terminal enol ethers results in complete recemisation of the product.
Tetrahedron Letters, 1995
The effect of the addition of water on the asymmetric oxidation of an acyl dithiane and an acyl d... more The effect of the addition of water on the asymmetric oxidation of an acyl dithiane and an acyl dithiolane has been studied. The use of enantiomerically pure dithiolane sulphoxides is demonstrated in a highly selective synthesis of (R)-3-benzoyloxy-2-butanone which depends upon a diastereoselective ketone reduction.
Tetrahedron, 2000
ABSTRACT Three protected new gallotannins, namely the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′... more ABSTRACT Three protected new gallotannins, namely the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′-hepta-O-acetylsucrose, the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′-hepta-O-benzoylsucrose and the 6,6′-di-O-tert-butyldiphenylsilyl-1′-O-(tri-O-methylgalloyl)-2,3,4,3′,4′-penta-O-acetylsucrose have been prepared in four short sequences from sucrose. Methods for rapid galloylation have been studied in order to avoid simultaneous acyl transfer reactions. A method for the deprotection of a tert-butyldiphenylsilyl ether has been developed which avoids the intramolecular migration of a benzoate group.
Tetrahedron, 2008
Microwave irradiation allows increasing the speed of several reactions and also offers the possib... more Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of a-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
Tetrahedron, 1999
A series tx-hydroxyalkyldithiolanes were reacted with a mixture of triphenylphosphine, diethyl az... more A series tx-hydroxyalkyldithiolanes were reacted with a mixture of triphenylphosphine, diethyl azodicarboxylate and hydrazoic acid to give 2-azido-l,4dithianes stereoselectively. Reduction of the azido group to an amine resulted in racemisation.
Tetrahedron, 1996
An efficient, practical and stereoselective route for the preparation of several polyols and thei... more An efficient, practical and stereoselective route for the preparation of several polyols and their corresponding lactols and lactones is described. They are promising precursors for the synthesis of several structurally interesting compounds.
Tetrahedron, 2012
ABSTRACT A wide range of N-phenylated secondary amines were prepared directly from 2-oxo-7-azobic... more ABSTRACT A wide range of N-phenylated secondary amines were prepared directly from 2-oxo-7-azobicyclo[4.1.0]heptanes using 4-nitrobenzoic acid as acid catalyst. The intermediate enol esters could also be isolated under similar conditions. A catalytic cycle is proposed.
Synthetic Communications, 2010
By reaction of C,N-diphenylnitrone and carbohydrates with a crotonyl side chain at their primary ... more By reaction of C,N-diphenylnitrone and carbohydrates with a crotonyl side chain at their primary or anomeric carbon position, we explore the application of sugar derivatives as raw materials and chiral inducers in microwave-assisted neat 1,3-dipolar cycloadditions.
Synlett, 2001
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Carbohydrate Polymers, 2015
6-O-methacryloyl-α-d-glucoside 2 and 4-bromophenyl-6-O-methacryloyl-d-glucothioside 7, obtained b... more 6-O-methacryloyl-α-d-glucoside 2 and 4-bromophenyl-6-O-methacryloyl-d-glucothioside 7, obtained by enzyme-catalyzed synthesis, have been homo-polymerized and copolymerized with styrene by a free radical process, yielding polymer materials with sugar moieties, attached to the polymer backbone via ester linkages. The results demonstrated that modifying the structural features of the monomers greatly affected the thermal and rheological properties of the polymers. The polymer materials obtained have been characterized by NMR, MALDI-MS, DSC, AFM, and EWC (equilibrium water content). The AFM images indicated the formation of spherical and core-shell polymeric microparticles.
Carbohydrate Research, 2014
The ubiquity of glycoconjugates in nature and their role in different biological processes, has l... more The ubiquity of glycoconjugates in nature and their role in different biological processes, has led to the development of several methodologies to synthesize these molecules. Synthetic glycoconjugates are now used to answer a variety of glycoconjugate-related biological questions and has provided new potential vaccines against cancer, viral and bacterial infections and new biotechnological tools. This review aims to collect and compile the recent advances in the field of glycopeptides, glycoproteins and glycolipid synthesis and also to update the previous reviews made on this subject. Finally, by highlighting the successes and failures of past research, we hope that this review will inspire fruitful research in this important medicinal chemistry field.
Tetrahedron, 2009
A short synthesis of the natural potent cytotoxic agent (−)-muricatacin 1 and related unsaturated... more A short synthesis of the natural potent cytotoxic agent (−)-muricatacin 1 and related unsaturated lactones from a versatile common intermediate, dienedioate 2, derived from d-mannitol or tartaric acid, is described. The strategy depends upon the desymmetrization of 7 by dihydroxylation and elaboration of the hydroxy alkyl sidechain. A route to unsaturated lactones is also described using a cis selective Wittig
Tetrahedron: Asymmetry, 2005
ABSTRACT Novel chiral C2-symmetric bis(oxazolines) were prepared from tartaric acid. They were ap... more ABSTRACT Novel chiral C2-symmetric bis(oxazolines) were prepared from tartaric acid. They were applied as ligands in the copper-catalyzed conjugate addition of diethylzinc to chalcone and 2-cyclohexenone. Maximum enantiomeric excesses of 50% and 53% were obtained, respectively. The sense of induction was found to depend on the configuration of the stereogenic centre in the oxazoline ring, and not on the stereogenic centres of the 1,4-dioxane backbone.
The Journal of Physical Chemistry A, 2008
The thermal decomposition of azidoacetone (CH 3 COCH 2 N 3) was studied using a combined experime... more The thermal decomposition of azidoacetone (CH 3 COCH 2 N 3) was studied using a combined experimental and computational approach. Flash pyrolysis at a range of temperatures (296-1250 K) was used to induce thermal decomposition, and the resulting products were expanded into a molecular beam and subsequently analyzed using electron bombardment ionization coupled to a quadrupole mass spectrometer. The advantages of this technique are that the parent molecules spend a very short time in the pyrolysis zone (20-30 µs) and that the subsequent expansion permits the stabilization of thermal products that are not observable using conventional pyrolysis methods. A detailed analysis of the mass spectra as a function of pyrolysis temperature revealed the participation of five thermal decomposition channels. Ab initio calculations on the stable structures and transition states of the azidoacetone system in combination with an analysis of the dissociative ionization pattern of each channel allowed the identity and mechanism of each channel to be elucidated. At low temperatures (296-800 K) the azide decomposes principally by the loss of N 2 to yield the imine (CH 3 COCHNH), which can further decompose to CH 3 CO and CHNH. At low and intermediate temperatures a process involving the loss of N 2 to yield CH 3 CHO and HCN is also open. Finally, at high temperatures (800-1250 K) a channel in which the azide decomposes to a stable cyclic amine (CO(CH 2) 2 NH) (after loss of N 2) is active. The last channel involves subsequent thermal decomposition of this cyclic amine to ketene (H 2 CCO) and methanimine (H 2 CNH).
Tetrahedron Letters, 1999
An asymmetric synthesis of (+)-epibatidine is described which uses the increased stereoselectivit... more An asymmetric synthesis of (+)-epibatidine is described which uses the increased stereoselectivity of a borohydride reduction induced by the presence of DMSO.
Tetrahedron Letters, 1993
A cyclopentane derivative elaborated from (-)-quinic acid has been converted efficiently and ster... more A cyclopentane derivative elaborated from (-)-quinic acid has been converted efficiently and stereoselectively into several cyclopentylamines, precursors to c'arhocyclic nucleosldes which have previously been shown to be biologzally mterestmg Recent reviews' on the subject of nucleoside synthesis and their activity as agents in the fight against the HIV and other viruses have highhghted the Importance of their carbocyclic analogues as possible treatments for AIDS. Carbovir 3 (B=guanine)1*2 has been the target of several research groups because of its high antiviral activity. Other polysubstituted
Tetrahedron Letters, 1994
Absfruct: Quinic acid is converted stereoselectively into a common cyclopentane intennediatc usef... more Absfruct: Quinic acid is converted stereoselectively into a common cyclopentane intennediatc useful for the synthesis of carbocyclii nucleoskks prostagkmdii and other importaut cyclopentane based compunds.
Tetrahedron Letters, 1989
Tetrahedron Letters, 1995
During studies related to the elaboration of prostaglandin precursors we have reduced the ketonic... more During studies related to the elaboration of prostaglandin precursors we have reduced the ketonic carbonyl group of a number of optically active 2-substituted-4-hydroxy-2-cyclopentenone esters and ethers using sodium borohydride and cerium trichloride under various conditions. High diastereoselectivity is achieved only with some 4-substituents.
Tetrahedron Letters, 1999
The novel chiral bis-acetal dioxane 2a derived from (2R,3R)-(+)-tartaric acid was shown to underg... more The novel chiral bis-acetal dioxane 2a derived from (2R,3R)-(+)-tartaric acid was shown to undergo an unexpected rearrangement upon treatment with lithium amide base to give the chiral dioxolane 3a in optically active form. Alkylation and aldol studies were performed on the diisopropyl ester of this dioxolane 3b.
Tetrahedron Letters, 1997
The sulphoxidation of the enol ethers of some acyldithiolanes using the Sharpless epoxidation rea... more The sulphoxidation of the enol ethers of some acyldithiolanes using the Sharpless epoxidation reagents followed by fluorolysis results in better overall stereoselectivity than direct oxidation of the acyldithiolane thus providing a highly stereoselective route to acyldithiolane sulphoxides. Fluorolysis under acid conditions of non terminal enol ethers results in complete recemisation of the product.
Tetrahedron Letters, 1995
The effect of the addition of water on the asymmetric oxidation of an acyl dithiane and an acyl d... more The effect of the addition of water on the asymmetric oxidation of an acyl dithiane and an acyl dithiolane has been studied. The use of enantiomerically pure dithiolane sulphoxides is demonstrated in a highly selective synthesis of (R)-3-benzoyloxy-2-butanone which depends upon a diastereoselective ketone reduction.
Tetrahedron, 2000
ABSTRACT Three protected new gallotannins, namely the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′... more ABSTRACT Three protected new gallotannins, namely the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′-hepta-O-acetylsucrose, the 6′-O-(tri-O-methylgalloyl)-2,3,4,6,1′,3′,4′-hepta-O-benzoylsucrose and the 6,6′-di-O-tert-butyldiphenylsilyl-1′-O-(tri-O-methylgalloyl)-2,3,4,3′,4′-penta-O-acetylsucrose have been prepared in four short sequences from sucrose. Methods for rapid galloylation have been studied in order to avoid simultaneous acyl transfer reactions. A method for the deprotection of a tert-butyldiphenylsilyl ether has been developed which avoids the intramolecular migration of a benzoate group.
Tetrahedron, 2008
Microwave irradiation allows increasing the speed of several reactions and also offers the possib... more Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of a-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
Tetrahedron, 1999
A series tx-hydroxyalkyldithiolanes were reacted with a mixture of triphenylphosphine, diethyl az... more A series tx-hydroxyalkyldithiolanes were reacted with a mixture of triphenylphosphine, diethyl azodicarboxylate and hydrazoic acid to give 2-azido-l,4dithianes stereoselectively. Reduction of the azido group to an amine resulted in racemisation.
Tetrahedron, 1996
An efficient, practical and stereoselective route for the preparation of several polyols and thei... more An efficient, practical and stereoselective route for the preparation of several polyols and their corresponding lactols and lactones is described. They are promising precursors for the synthesis of several structurally interesting compounds.
Tetrahedron, 2012
ABSTRACT A wide range of N-phenylated secondary amines were prepared directly from 2-oxo-7-azobic... more ABSTRACT A wide range of N-phenylated secondary amines were prepared directly from 2-oxo-7-azobicyclo[4.1.0]heptanes using 4-nitrobenzoic acid as acid catalyst. The intermediate enol esters could also be isolated under similar conditions. A catalytic cycle is proposed.
Synthetic Communications, 2010
By reaction of C,N-diphenylnitrone and carbohydrates with a crotonyl side chain at their primary ... more By reaction of C,N-diphenylnitrone and carbohydrates with a crotonyl side chain at their primary or anomeric carbon position, we explore the application of sugar derivatives as raw materials and chiral inducers in microwave-assisted neat 1,3-dipolar cycloadditions.
Synlett, 2001
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.