Renata Riva - Academia.edu (original) (raw)
Papers by Renata Riva
Advances in Experimental Medicine and Biology, 2010
Multi-component reactions (MCRs) have now been well established as a powerful synthetic tool for ... more Multi-component reactions (MCRs) have now been well established as a powerful synthetic tool for creating molecular complexity and diversity and are undoubtedly well suited for the drug discovery program. Another potential that has probably received less attention among synthetic chemists is the opportunity offered by MCRs for the development of new fundamentally important transformations (reactions). Indeed, although an MCR is
Advances in Experimental Medicine and Biology, 2010
Ketenimines are a class of versatile and highly reactive intermediates that can participate in a ... more Ketenimines are a class of versatile and highly reactive intermediates that can participate in a variety of organic reactions, such as nucleophilic additions, radical additions, [2 + 2] and [2 + 4] cycloadditions, and sigmatropic rearrangements. In this presentation, we report on a series of multi-component reactions that involve a ketenimine intermediate. These reactions could furnish diverse heterocyclic compounds, including functionalized iminocoumarin, iminodihydroqunolines, iminothiochromens, pyrrolines, isoquinolines, pyridines, b-lactams, imino-1,2-dihydrocoumarins, and benzimidazoles.
Journal of the Chemical Society, Chemical Communications, 1987
$ In our hands elaboration of this intermediate according to Isobe's protocol (ref. 2) g... more $ In our hands elaboration of this intermediate according to Isobe's protocol (ref. 2) gave noticeably poorer yields of (5). ... References 1 C. Szantay, G. Blask6, K. Honty, and D. Dorney, 'Corynantheine, Yohimbine, and Related Alkaloids' in 'The Alkaloids,' ed. A. Brossi, ...
Organic Reactions, 2004
ABSTRACT
Multicomponent Reactions in Organic Synthesis, 2014
ABSTRACT Multicomponent reactions (MCRs) often proceed as redox processes, where two or more comp... more ABSTRACT Multicomponent reactions (MCRs) often proceed as redox processes, where two or more components change their oxidation state, alternatively increasing and lowering it. This chapter illustrates MCRs performed under oxidative conditions, with critical discussion of the advantages of these approaches in cases where the same final products could be obtained also by traditional MCRs. Transformations involving in situ oxidation of one reagent are discussed first, classified according to the type of multicomponent reaction. Then, the chapter illustrates examples of transformations involving oxidation of a reaction intermediate. MCRs where the external oxidant acts as Lewis acid instead of playing its usual role can also be found in the literature, although in this case no oxidative process is taking place.
Tetrahedron: Asymmetry, 2004
A new efficient chemoenzymatic methodology for the production of 3-O-benzyl-sn-glycerol and 1,2-O... more A new efficient chemoenzymatic methodology for the production of 3-O-benzyl-sn-glycerol and 1,2-O-dipalmitoyl-sn-glycerol has been developed. It starts from racemic 1-O-benzylglycerol and is based on the sequential enzymatic acylation––Mitsunobu inversion––enzymatic hydrolysis, which has been performed without isolation of the intermediates. In this way a 70–75% yield of 3-O-benzyl-sn-glycerol with 94–96% ee has been obtained.
Tetrahedron: Asymmetry, 1995
The effect of various experimental variables (solvent, methodology of supportation on celite, pre... more The effect of various experimental variables (solvent, methodology of supportation on celite, presence of water, conversion and so on) on the rate and on the enantioselectivity of monoacetylation of some prochiral 2-substituted-1,3-propanediols with vinyl acetate catalyzed by crude PPL (pig pancreatic lipase) was analyzed. This study allowed to assess the best conditions for performing these transformations, providing an efficient methodology
Tetrahedron: Asymmetry, 1998
2-(2-Quinolyl)-and 2-(4-quinolyl)-1,3-propanediols 3 and 4 were prepared and asymmetrized by enan... more 2-(2-Quinolyl)-and 2-(4-quinolyl)-1,3-propanediols 3 and 4 were prepared and asymmetrized by enantioselective acetylation in organic solvent catalyzed by lipases. While monoacetate 5 was best obtained using Celitesupported pig pancreatic lipase (PPL) (97.3% e.e.) as the (R)-enantiomer, both enantiomers of 6 have been obtained using different enzymes: (R)-6 using lipase from Aspergillus niger (84.0% e.e.) and (S)-6 using lipase from Candida antarctica (97.5% e.e.). The absolute configuration of both monoacetates 5 and 6 has been determined by anomalous X-ray dispersion methodology on the corresponding p-bromobenzoates 11 and 12.
Tetrahedron: Asymmetry, 1994
Chem. 1992, 57, 3231-3236. Guanti, G.; Banfi, L.; Riva, R.; Zannetti, M. T. Telrakedron Lett. 199... more Chem. 1992, 57, 3231-3236. Guanti, G.; Banfi, L.; Riva, R.; Zannetti, M. T. Telrakedron Lett. 1993, 34, 5483.5486, and refs. therein. Guanti, 0.; Banfi, L.; Merlo, V.; Narisano. E.; Thea, S. Tetrahedron 1993,49, 9501-9516. a) Riva, R.; Banft, L.; Danieli, B.; Guanti, G.; Lesma, G.; Palmisano, G. J. Chem. Sot., Chem. Commun. 1987, 299-300; b) D;mreli. B : lesma, 0.: Maul-o, M.; Palmisano. G.; Passmel)& D.
Tetrahedron Letters, 1993
Both enantiomers of compound 3, a possible intermediate for the AB ring system 2 of Aklavinone 1,... more Both enantiomers of compound 3, a possible intermediate for the AB ring system 2 of Aklavinone 1, were obtained in optically active form from diol 7. Key steps were the preparation of both enantiomers of monoacetate 8d, via enzymatic reacrions that utilize PPL as catalyst, and the construction of ring A in a totally regioselective manner.
Tetrahedron Letters, 1986
... ENZYMES IN ASYMMETRIC SYNTHESIS: EFFECT 0F REACTION MEDIA ON THE PLE CATALYSED HYDROLYSIS OF ... more ... ENZYMES IN ASYMMETRIC SYNTHESIS: EFFECT 0F REACTION MEDIA ON THE PLE CATALYSED HYDROLYSIS OF DIESTERS1 Giuseppe Guanti Luca Banfi, Enrica Narisano, Renate Riva,2 and ... T. Kokubo, T. Uchida, S. Tanimoto, M. Okano, T. Sugimoto, Tetrahedron Lett. ...
Tetrahedron Letters, 1991
MgBr2 catalysed allylation of a series of diprotected asymmetrixed his (hydroxymethyl)acetaldehyd... more MgBr2 catalysed allylation of a series of diprotected asymmetrixed his (hydroxymethyl)acetaldehydes 2 with allyltributylstannane proceeds with good diastereoselectivity.
Tetrahedron Letters, 1992
4-(3-hydroxyphenylj-butanoates4, on treatment with DIBALH, followed by hydrolytic work-up, underg... more 4-(3-hydroxyphenylj-butanoates4, on treatment with DIBALH, followed by hydrolytic work-up, undergo a novel completely regioselective intramolecular hydroxyalkylation reaction to give 1,8-dihydroxytetralins. The yield of the reaction depends heavily on the structure of starting material, best results being achieved with 3,3-disubstituted butanoates.
![Research paper thumbnail of Multicomponent approach to the alkaloid-type 2-aza-7-oxabicyclo[4.3.0]nonane framework](https://attachments.academia-assets.com/51522138/thumbnails/1.jpg)
](Tetrahedron Letters, 2012
a b s t r a c t N-Allyl 3-endo-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid has been... more a b s t r a c t N-Allyl 3-endo-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid has been synthesized and has been employed in a Ugi-5-centre-4-component reaction (U-5C-4CR) with various aldehydes and isocyanides; by employing a mixture of methanol and trifluoroethanol the reaction was completely stereoselective. The resulting products have been employed in an unprecedented ring-opening/ring-closing metathesis process with Ru catalyst, to afford stereochemically defined, polysubstituted cis-fused hexahydrofuro[3,2-b]pyridine derivatives in moderate to good yields. This straightforward procedure allows to assemble in just two synthetic steps natural product-like compounds having the 2-aza-7-oxabicyclo [4.3.0]nonane framework, displayed by various alkaloids.
Tetrahedron Letters, 2004
Intramolecular Ugi reactions with bicyclic b-amino acids have been performed and the effects of t... more Intramolecular Ugi reactions with bicyclic b-amino acids have been performed and the effects of the configuration and N-alkylation have been studied. We have proven that preferential ring contraction or nucleophilic attack by the solvent depend not only on the presence of N-alkylation but also on the relative disposition of the carboxyl group and the amine. Excellent results in terms of stereoselectivity have been obtained in the case of N-alkyl-3-exo-amino-7-oxabicyclo[2.2.1]-2-endo-carboxylic acids.
Tetrahedron Letters, 2005
a-acyloxyaminoamides can be prepared, with yields ranging from fair to very good (up to 89%), thr... more a-acyloxyaminoamides can be prepared, with yields ranging from fair to very good (up to 89%), through an Ugi four component reaction by mixing a carbonyl component, a carboxylic acid, an isocyanide and an N-alkylated hydroxylamine in methanol. Preformed nitrones furnish the same final compounds with comparable yields.
Advances in Experimental Medicine and Biology, 2010
Multi-component reactions (MCRs) have now been well established as a powerful synthetic tool for ... more Multi-component reactions (MCRs) have now been well established as a powerful synthetic tool for creating molecular complexity and diversity and are undoubtedly well suited for the drug discovery program. Another potential that has probably received less attention among synthetic chemists is the opportunity offered by MCRs for the development of new fundamentally important transformations (reactions). Indeed, although an MCR is
Advances in Experimental Medicine and Biology, 2010
Ketenimines are a class of versatile and highly reactive intermediates that can participate in a ... more Ketenimines are a class of versatile and highly reactive intermediates that can participate in a variety of organic reactions, such as nucleophilic additions, radical additions, [2 + 2] and [2 + 4] cycloadditions, and sigmatropic rearrangements. In this presentation, we report on a series of multi-component reactions that involve a ketenimine intermediate. These reactions could furnish diverse heterocyclic compounds, including functionalized iminocoumarin, iminodihydroqunolines, iminothiochromens, pyrrolines, isoquinolines, pyridines, b-lactams, imino-1,2-dihydrocoumarins, and benzimidazoles.
Journal of the Chemical Society, Chemical Communications, 1987
$ In our hands elaboration of this intermediate according to Isobe's protocol (ref. 2) g... more $ In our hands elaboration of this intermediate according to Isobe's protocol (ref. 2) gave noticeably poorer yields of (5). ... References 1 C. Szantay, G. Blask6, K. Honty, and D. Dorney, 'Corynantheine, Yohimbine, and Related Alkaloids' in 'The Alkaloids,' ed. A. Brossi, ...
Organic Reactions, 2004
ABSTRACT
Multicomponent Reactions in Organic Synthesis, 2014
ABSTRACT Multicomponent reactions (MCRs) often proceed as redox processes, where two or more comp... more ABSTRACT Multicomponent reactions (MCRs) often proceed as redox processes, where two or more components change their oxidation state, alternatively increasing and lowering it. This chapter illustrates MCRs performed under oxidative conditions, with critical discussion of the advantages of these approaches in cases where the same final products could be obtained also by traditional MCRs. Transformations involving in situ oxidation of one reagent are discussed first, classified according to the type of multicomponent reaction. Then, the chapter illustrates examples of transformations involving oxidation of a reaction intermediate. MCRs where the external oxidant acts as Lewis acid instead of playing its usual role can also be found in the literature, although in this case no oxidative process is taking place.
Tetrahedron: Asymmetry, 2004
A new efficient chemoenzymatic methodology for the production of 3-O-benzyl-sn-glycerol and 1,2-O... more A new efficient chemoenzymatic methodology for the production of 3-O-benzyl-sn-glycerol and 1,2-O-dipalmitoyl-sn-glycerol has been developed. It starts from racemic 1-O-benzylglycerol and is based on the sequential enzymatic acylation––Mitsunobu inversion––enzymatic hydrolysis, which has been performed without isolation of the intermediates. In this way a 70–75% yield of 3-O-benzyl-sn-glycerol with 94–96% ee has been obtained.
Tetrahedron: Asymmetry, 1995
The effect of various experimental variables (solvent, methodology of supportation on celite, pre... more The effect of various experimental variables (solvent, methodology of supportation on celite, presence of water, conversion and so on) on the rate and on the enantioselectivity of monoacetylation of some prochiral 2-substituted-1,3-propanediols with vinyl acetate catalyzed by crude PPL (pig pancreatic lipase) was analyzed. This study allowed to assess the best conditions for performing these transformations, providing an efficient methodology
Tetrahedron: Asymmetry, 1998
2-(2-Quinolyl)-and 2-(4-quinolyl)-1,3-propanediols 3 and 4 were prepared and asymmetrized by enan... more 2-(2-Quinolyl)-and 2-(4-quinolyl)-1,3-propanediols 3 and 4 were prepared and asymmetrized by enantioselective acetylation in organic solvent catalyzed by lipases. While monoacetate 5 was best obtained using Celitesupported pig pancreatic lipase (PPL) (97.3% e.e.) as the (R)-enantiomer, both enantiomers of 6 have been obtained using different enzymes: (R)-6 using lipase from Aspergillus niger (84.0% e.e.) and (S)-6 using lipase from Candida antarctica (97.5% e.e.). The absolute configuration of both monoacetates 5 and 6 has been determined by anomalous X-ray dispersion methodology on the corresponding p-bromobenzoates 11 and 12.
Tetrahedron: Asymmetry, 1994
Chem. 1992, 57, 3231-3236. Guanti, G.; Banfi, L.; Riva, R.; Zannetti, M. T. Telrakedron Lett. 199... more Chem. 1992, 57, 3231-3236. Guanti, G.; Banfi, L.; Riva, R.; Zannetti, M. T. Telrakedron Lett. 1993, 34, 5483.5486, and refs. therein. Guanti, 0.; Banfi, L.; Merlo, V.; Narisano. E.; Thea, S. Tetrahedron 1993,49, 9501-9516. a) Riva, R.; Banft, L.; Danieli, B.; Guanti, G.; Lesma, G.; Palmisano, G. J. Chem. Sot., Chem. Commun. 1987, 299-300; b) D;mreli. B : lesma, 0.: Maul-o, M.; Palmisano. G.; Passmel)& D.
Tetrahedron Letters, 1993
Both enantiomers of compound 3, a possible intermediate for the AB ring system 2 of Aklavinone 1,... more Both enantiomers of compound 3, a possible intermediate for the AB ring system 2 of Aklavinone 1, were obtained in optically active form from diol 7. Key steps were the preparation of both enantiomers of monoacetate 8d, via enzymatic reacrions that utilize PPL as catalyst, and the construction of ring A in a totally regioselective manner.
Tetrahedron Letters, 1986
... ENZYMES IN ASYMMETRIC SYNTHESIS: EFFECT 0F REACTION MEDIA ON THE PLE CATALYSED HYDROLYSIS OF ... more ... ENZYMES IN ASYMMETRIC SYNTHESIS: EFFECT 0F REACTION MEDIA ON THE PLE CATALYSED HYDROLYSIS OF DIESTERS1 Giuseppe Guanti Luca Banfi, Enrica Narisano, Renate Riva,2 and ... T. Kokubo, T. Uchida, S. Tanimoto, M. Okano, T. Sugimoto, Tetrahedron Lett. ...
Tetrahedron Letters, 1991
MgBr2 catalysed allylation of a series of diprotected asymmetrixed his (hydroxymethyl)acetaldehyd... more MgBr2 catalysed allylation of a series of diprotected asymmetrixed his (hydroxymethyl)acetaldehydes 2 with allyltributylstannane proceeds with good diastereoselectivity.
Tetrahedron Letters, 1992
4-(3-hydroxyphenylj-butanoates4, on treatment with DIBALH, followed by hydrolytic work-up, underg... more 4-(3-hydroxyphenylj-butanoates4, on treatment with DIBALH, followed by hydrolytic work-up, undergo a novel completely regioselective intramolecular hydroxyalkylation reaction to give 1,8-dihydroxytetralins. The yield of the reaction depends heavily on the structure of starting material, best results being achieved with 3,3-disubstituted butanoates.
Tetrahedron Letters, 2012
a b s t r a c t N-Allyl 3-endo-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid has been... more a b s t r a c t N-Allyl 3-endo-amino-7-oxabicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid has been synthesized and has been employed in a Ugi-5-centre-4-component reaction (U-5C-4CR) with various aldehydes and isocyanides; by employing a mixture of methanol and trifluoroethanol the reaction was completely stereoselective. The resulting products have been employed in an unprecedented ring-opening/ring-closing metathesis process with Ru catalyst, to afford stereochemically defined, polysubstituted cis-fused hexahydrofuro[3,2-b]pyridine derivatives in moderate to good yields. This straightforward procedure allows to assemble in just two synthetic steps natural product-like compounds having the 2-aza-7-oxabicyclo [4.3.0]nonane framework, displayed by various alkaloids.
Tetrahedron Letters, 2004
Intramolecular Ugi reactions with bicyclic b-amino acids have been performed and the effects of t... more Intramolecular Ugi reactions with bicyclic b-amino acids have been performed and the effects of the configuration and N-alkylation have been studied. We have proven that preferential ring contraction or nucleophilic attack by the solvent depend not only on the presence of N-alkylation but also on the relative disposition of the carboxyl group and the amine. Excellent results in terms of stereoselectivity have been obtained in the case of N-alkyl-3-exo-amino-7-oxabicyclo[2.2.1]-2-endo-carboxylic acids.
Tetrahedron Letters, 2005
a-acyloxyaminoamides can be prepared, with yields ranging from fair to very good (up to 89%), thr... more a-acyloxyaminoamides can be prepared, with yields ranging from fair to very good (up to 89%), through an Ugi four component reaction by mixing a carbonyl component, a carboxylic acid, an isocyanide and an N-alkylated hydroxylamine in methanol. Preformed nitrones furnish the same final compounds with comparable yields.