Antonio Burtoloso - Academia.edu (original) (raw)

Papers by Antonio Burtoloso

Catalysts

Sulfur ylides are an important class of organic compounds due to their ability to perform many di... more Sulfur ylides are an important class of organic compounds due to their ability to perform many different transformations that can give diverse and interesting products with a high degree of complexity. Although metal-catalyzed transformations are frequent in this class of compounds, organocatalyzed transformations remain scarce. From initial works, this review aims to show organocatalyzed transformations from sulfur ylides, involving cyclopropanation and formal N–H, S–H, and C–H insertion reactions, including enantioselective versions. The proposed mechanisms and the modes of activation of these organocatalysts will be covered. Furthermore, advances in this area and potential challenges to be circumvented in the near future will also be discussed.

European Journal of Organic Chemistry, 2020

Substituted naphthols (SNs) are an important class of chemical compounds present in many natural ... more Substituted naphthols (SNs) are an important class of chemical compounds present in many natural and synthetic products with biological and pharmaceutical activities. Moreover, the naphthol skeleton has been employed as a starting material for the development of drug molecules and natural products. Thus, different synthetic methods to access naphthol cores have been reported using diverse starting materials and chemical strategies. This review article describes literature on synthetic methodologies of substituted naphthols synthesized from alkynes, sulfur ylides, diazo substrates, alkenes/cyclopropenes, ketones/oxanorbenes/furans, amongst other key reactants.

The Chemical Record, 2021

The importance of gem‐difunctionalized ketones is represented by their broad applications across ... more The importance of gem‐difunctionalized ketones is represented by their broad applications across chemical boundaries over recent years. The interesting reactivities that this class of compounds possess have made them ideal building blocks to access high‐value organic molecules. Furthermore, the gem‐difunctionalized ketone moiety has featured in numerous bioactive molecules. For these reasons, a plethora of routes to access such significant molecules have been developed by research groups worldwide – this account looks at delineating the synthesis of gem‐difunctionalized ketones from carbonyl substrates, diazo compounds, sulfur ylides and alkynyl reactants.

Angewandte Chemie, 2020

The first example of enantioselective S−H insertion reactions of sulfoxonium ylides is reported. ... more The first example of enantioselective S−H insertion reactions of sulfoxonium ylides is reported. Under the influence of thiourea catalysis, excellent levels of enantiocontrol (up to 95 % ee) and yields (up to 97 %) are achieved for 31 examples in S−H insertion reactions of aryl thiols and α‐carbonyl sulfoxonium ylides.

Organic Letters, 2019

The short and stereoselective syntheses of diterpenes (±)-brussonol and (±)-komaroviquinone, via ... more The short and stereoselective syntheses of diterpenes (±)-brussonol and (±)-komaroviquinone, via a Nicatalyzed epoxide ring-opening approach in the presence of aryl halides, is described. Key steps involve the effective preparation of a challenging hemiacetal intermediate in a single operation, followed by a highly efficient BF 3 •OEt 2-catalyzed Friedel−Craft alkylation, to construct the tricyclic skeleton of these diterpenes. The synthetic approach might offer a unified route for the synthesis of several natural products containing icetexane motifs.

ChemistrySelect, 2018

The synthesis of several pyrrolidones (PYR), including a highly complex tetracyclic one (40‐91% y... more The synthesis of several pyrrolidones (PYR), including a highly complex tetracyclic one (40‐91% yields), is described employing an inexpensive iron catalyst and aqueous solutions of biomass‐derived levulinic acid (LA) and formic acid (FA). The method is broad since it works with many structurally different amines. Considering that all produced LA from a real biorefinery facility will most probably be further derivatized directly from the hydrolysed biomass in aqueous solutions (without isolation), this method furnishes many advantages when compared to previous ones that employ different solvents or neat LA.

Frontiers in Chemistry, 2019

A Brønsted acid catalyzed intramolecular cyclization of N-Cbz-protected diazoketones, derived fro... more A Brønsted acid catalyzed intramolecular cyclization of N-Cbz-protected diazoketones, derived from α-amino acids, is described. The reaction proceeds under metal-free conditions and is promoted by ecofriendly silica-supported HClO 4 as the catalyst and methanol as the solvent. This transformation enables the short synthesis of various 1,3-oxazinane-2,5-diones under mild reaction conditions and in good yields (up to 90%). The setup is very simple; by just mixing all reagents together with no work-up necessary before purification, this protocol takes a greener approach.

Nature Protocols, 2018

There is considerable interest in the development of chemical methods for the precise, site-selec... more There is considerable interest in the development of chemical methods for the precise, site-selective modification of antibodies for therapeutic applications. In this protocol, we describe a strategy for the irreversible and selective modification of cysteine residues on antibodies, using functionalized carbonylacrylic reagents. This protocol is based on a thiol-Michael-type addition of native or engineered cysteine residues to carbonylacrylic reagents equipped with functional compounds such as cytotoxic drugs. This approach is a robust alternative to the conventional maleimide technique; the reaction is irreversible and uses synthetically accessible reagents. Complete conversion to the conjugates, with improved quality and homogeneity, is often achieved using a minimal excess (typically between 5 and 10 equiv.) of the carbonylacrylic reagent. Potential applications of this method cover a broad scope of cysteine-tagged antibodies in various formats (full-length IgGs, nanobodies) for the site-selective incorporation of cytotoxic drugs without loss of antigenbinding affinity. Both the synthesis of the carbonylacrylic reagent armed with a synthetic molecule of interest and the subsequent preparation of the chemically defined, homogeneous antibody conjugate can be achieved within 48 h and can be easily performed by nonspecialists. Importantly, the conjugates formed are stable in human plasma. The use of liquid chromatography-mass spectrometry (LC-MS) analysis is recommended for monitoring the progression of the bioconjugation reactions on protein and antibody substrates with accurate resolution.

Organic Letters, 2018

A general, mild, and versatile synthesis of the challenging α-aryl-β-ketosulfoxonium ylides has b... more A general, mild, and versatile synthesis of the challenging α-aryl-β-ketosulfoxonium ylides has been developed for the first time, substituting traditional methods starting from diazo compounds. The arylation of easily accessible βketosulfoxonium ylides using aryne chemistry allowed the preparation of a large scope of the pro-chiral ylides in very good yields (40 examples; up to 85%). As applications, these ylides were smoothly converted into α-aryl ketones after desulfurization in good yields (up to 98%) as well as in other important derivatives.

The Journal of organic chemistry, Jan 21, 2018

Insertion reactions of diazo carbonyls to azlactones in basic conditions have been performed. The... more Insertion reactions of diazo carbonyls to azlactones in basic conditions have been performed. The developed method allows the preparation of a wide range of oxazole derivatives in yields ranging from 74 to 98%. Different substituents on both azlactone rings and diazo carbonyls do not compromise the methodology, even those containing stereogenic centers. Isotopic labeling experiments revealed the mechanism may proceed through a rare diazo carbonyl activation by an ammonium salt derivative.

European Journal of Organic Chemistry, 2018

Tri‐substituted cyclopentadienes and cyclopentanes, high‐value‐added compounds, are readily prepa... more Tri‐substituted cyclopentadienes and cyclopentanes, high‐value‐added compounds, are readily prepared from ethyl levulinate, a chemical platform easily obtained from biomass. Key steps involve coupling two molecules of ethyl levulinate in the presence of pyrrolidine, followed by a base‐catalyzed intramolecular aldol condensation, to provide a singly‐purified and easily derivatizable cyclopentadiene in almost 40 % isolated overall yield. Reaction conditions are mild, simple and employ green solvents such as ethanol and anisole. This method opens a new pathway to preparing complex molecules from renewable feedstocks.

Chemistry - A European Journal, 2017

A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkylhalides is de... more A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkylhalides is described. The method furnishes several gem-difunctionalized haloketones (an alkyl and F, Cl, Br, or I) in good yields. Replacing alkyhalides with a mixture of electrophilic halogen species and various halide anions led to gemdihalogenated ketones containing a combination of the same or two different halogens. Kinetic isotopic effects as well as reaction kinetic experiments give insight to the mechanism of these reactions. Sulfur ylides were described in 1930 by Ingold and Jessop. 1 Although almost 90 years has passed, most applications involving these compounds are related to the pioneering work developed by Johnson and LaCount, 2 Franzen, 3 and Corey and Chaykovsky 4 in the 1960s. For example, cyclopropanation, epoxidation, and aziridination reactions as well as [2,3] sigmatropic rearrangements are most commonly used. 5 New transformations employing sulfur ylides have been described in more recent years, 5,6 but this has occurred less frequently than expected when compared to other classes of compounds.

Bioorganic & medicinal chemistry letters, Nov 15, 2017

The effects on potency of cruzain inhibition of replacing a nitrile group with alternative warhea... more The effects on potency of cruzain inhibition of replacing a nitrile group with alternative warheads were explored. The oxime was almost an order of magnitude more potent than the corresponding nitrile and has the potential to provide access to the prime side of the catalytic site. Dipeptide aldehydes and azadipeptide nitriles were found to be two orders of magnitude more potent cruzain inhibitors than the corresponding dipeptide nitriles although potency differences were modulated by substitution at P1 and P3. Replacement of the α methylene of a dipeptide aldehyde with cyclopropane led to a loss of potency of almost three orders of magnitude. The vinyl esters and amides that were characterized as reversible inhibitors were less potent than the corresponding nitrile by between one and two orders of magnitude.

Chemical Communications, 2015

The direct conversion of LA, from crude liquors after biomass acid hydrolysis, into GVL is achiev... more The direct conversion of LA, from crude liquors after biomass acid hydrolysis, into GVL is achieved using Fe catalysts.

ACS Sustainable Chemistry & Engineering, 2017

Described are the selectivities observed for reactions of lignin model compounds with modificatio... more Described are the selectivities observed for reactions of lignin model compounds with modifications of the copper-doped porous metal oxide (CuPMO) system previously shown to be a catalyst for lignin disassembly in super-critical methanol (Matson et al, J. Amer. Chem. Soc. 2011, 133, 14090-14097). The models studied are benzyl phenyl ether, 2phenylethyl phenyl ether, diphenyl ether, biphenyl and 2,3 dihydrobenzofuran, which are respective mimetics of the α-O-4, β-O-4, 4-O-5, 5-5 and β-5 linkages characteristic of lignin. Also briefly investigated as a substrate is poplar organosolv lignin. The catalyst modifications included added samarium(III) (both homogeneous and heterogeneous) or formic acid. The highest activity for the hydrogenolysis of aryl ether linkages was noted for catalysts with Sm(III) incorporated into the solid matrix of the PMO structure. In contrast, simply adding Sm 3+ salts to the solution suppressed the hydrogenolysis activity. Added formic acid suppressed aryl ether hydrogenolysis, presumably by neutralizing base sites on the PMO surface but at the same time improved the selectivity toward aromatic products. Acetic acid induced similar reactivity changes. While these materials were variously successful in catalyzing the hydrogenolysis of the different ethers, there was very little activity toward the cleavage of the 5-5 and β-5 CC bonds that represent a small, but significant, percentage of the linkages between monolignol units in lignins..

The Journal of Organic Chemistry, 2016

Proceedings of the 15th Brazilian Meeting on Organic Synthesis Proceedings, 2013

Accounts of chemical research, Jan 19, 2015

Among the different types of diazocarbonyl substrates found in the literature to date, α,β-unsatu... more Among the different types of diazocarbonyl substrates found in the literature to date, α,β-unsaturated diazoketones have proven to be very promising as multifunctional intermediates. Possessing a diazo group, a ketone function and a double bond all together in a single molecule, these compounds constitute versatile building blocks for synthesis. For example, double bond functionalization, followed by intramolecular insertion reactions, can be a short alternative to prepare several rings or heterocyclic compounds. Although there are many efficient methods to prepare diazoketones, very few can be extended to the synthesis of the a,β-unsaturated diazoketones; this is likely responsible for their limited application in synthesis. Unfortunately, the classical methods to prepare saturated- or aryl-diazoketones (acylation of diazomethane with acyl chlorides or mixed anhydrides) are not suitable for preparing a,β-unsaturated diazoketones, since pyrazolines (dipolar cycloaddition products fr...

Proceedings of the 15th Brazilian Meeting on Organic Synthesis Proceedings, 2013

Journal of Molecular Structure: THEOCHEM, 2005

In the last years, Kenji Koga and co-workers [1a], [1b], [1c] and [1d] developed a new methodolog... more In the last years, Kenji Koga and co-workers [1a], [1b], [1c] and [1d] developed a new methodology for the asymmetric synthesis of α,α-dialkyl β-ketoesters in high enantiomeric excess. These ketoesters were prepared via the alkylation of chiral lithium enamines (3) derived from α-alkyl β-...

Catalysts

Sulfur ylides are an important class of organic compounds due to their ability to perform many di... more Sulfur ylides are an important class of organic compounds due to their ability to perform many different transformations that can give diverse and interesting products with a high degree of complexity. Although metal-catalyzed transformations are frequent in this class of compounds, organocatalyzed transformations remain scarce. From initial works, this review aims to show organocatalyzed transformations from sulfur ylides, involving cyclopropanation and formal N–H, S–H, and C–H insertion reactions, including enantioselective versions. The proposed mechanisms and the modes of activation of these organocatalysts will be covered. Furthermore, advances in this area and potential challenges to be circumvented in the near future will also be discussed.

European Journal of Organic Chemistry, 2020

Substituted naphthols (SNs) are an important class of chemical compounds present in many natural ... more Substituted naphthols (SNs) are an important class of chemical compounds present in many natural and synthetic products with biological and pharmaceutical activities. Moreover, the naphthol skeleton has been employed as a starting material for the development of drug molecules and natural products. Thus, different synthetic methods to access naphthol cores have been reported using diverse starting materials and chemical strategies. This review article describes literature on synthetic methodologies of substituted naphthols synthesized from alkynes, sulfur ylides, diazo substrates, alkenes/cyclopropenes, ketones/oxanorbenes/furans, amongst other key reactants.

The Chemical Record, 2021

The importance of gem‐difunctionalized ketones is represented by their broad applications across ... more The importance of gem‐difunctionalized ketones is represented by their broad applications across chemical boundaries over recent years. The interesting reactivities that this class of compounds possess have made them ideal building blocks to access high‐value organic molecules. Furthermore, the gem‐difunctionalized ketone moiety has featured in numerous bioactive molecules. For these reasons, a plethora of routes to access such significant molecules have been developed by research groups worldwide – this account looks at delineating the synthesis of gem‐difunctionalized ketones from carbonyl substrates, diazo compounds, sulfur ylides and alkynyl reactants.

Angewandte Chemie, 2020

The first example of enantioselective S−H insertion reactions of sulfoxonium ylides is reported. ... more The first example of enantioselective S−H insertion reactions of sulfoxonium ylides is reported. Under the influence of thiourea catalysis, excellent levels of enantiocontrol (up to 95 % ee) and yields (up to 97 %) are achieved for 31 examples in S−H insertion reactions of aryl thiols and α‐carbonyl sulfoxonium ylides.

Organic Letters, 2019

The short and stereoselective syntheses of diterpenes (±)-brussonol and (±)-komaroviquinone, via ... more The short and stereoselective syntheses of diterpenes (±)-brussonol and (±)-komaroviquinone, via a Nicatalyzed epoxide ring-opening approach in the presence of aryl halides, is described. Key steps involve the effective preparation of a challenging hemiacetal intermediate in a single operation, followed by a highly efficient BF 3 •OEt 2-catalyzed Friedel−Craft alkylation, to construct the tricyclic skeleton of these diterpenes. The synthetic approach might offer a unified route for the synthesis of several natural products containing icetexane motifs.

ChemistrySelect, 2018

The synthesis of several pyrrolidones (PYR), including a highly complex tetracyclic one (40‐91% y... more The synthesis of several pyrrolidones (PYR), including a highly complex tetracyclic one (40‐91% yields), is described employing an inexpensive iron catalyst and aqueous solutions of biomass‐derived levulinic acid (LA) and formic acid (FA). The method is broad since it works with many structurally different amines. Considering that all produced LA from a real biorefinery facility will most probably be further derivatized directly from the hydrolysed biomass in aqueous solutions (without isolation), this method furnishes many advantages when compared to previous ones that employ different solvents or neat LA.

Frontiers in Chemistry, 2019

A Brønsted acid catalyzed intramolecular cyclization of N-Cbz-protected diazoketones, derived fro... more A Brønsted acid catalyzed intramolecular cyclization of N-Cbz-protected diazoketones, derived from α-amino acids, is described. The reaction proceeds under metal-free conditions and is promoted by ecofriendly silica-supported HClO 4 as the catalyst and methanol as the solvent. This transformation enables the short synthesis of various 1,3-oxazinane-2,5-diones under mild reaction conditions and in good yields (up to 90%). The setup is very simple; by just mixing all reagents together with no work-up necessary before purification, this protocol takes a greener approach.

Nature Protocols, 2018

There is considerable interest in the development of chemical methods for the precise, site-selec... more There is considerable interest in the development of chemical methods for the precise, site-selective modification of antibodies for therapeutic applications. In this protocol, we describe a strategy for the irreversible and selective modification of cysteine residues on antibodies, using functionalized carbonylacrylic reagents. This protocol is based on a thiol-Michael-type addition of native or engineered cysteine residues to carbonylacrylic reagents equipped with functional compounds such as cytotoxic drugs. This approach is a robust alternative to the conventional maleimide technique; the reaction is irreversible and uses synthetically accessible reagents. Complete conversion to the conjugates, with improved quality and homogeneity, is often achieved using a minimal excess (typically between 5 and 10 equiv.) of the carbonylacrylic reagent. Potential applications of this method cover a broad scope of cysteine-tagged antibodies in various formats (full-length IgGs, nanobodies) for the site-selective incorporation of cytotoxic drugs without loss of antigenbinding affinity. Both the synthesis of the carbonylacrylic reagent armed with a synthetic molecule of interest and the subsequent preparation of the chemically defined, homogeneous antibody conjugate can be achieved within 48 h and can be easily performed by nonspecialists. Importantly, the conjugates formed are stable in human plasma. The use of liquid chromatography-mass spectrometry (LC-MS) analysis is recommended for monitoring the progression of the bioconjugation reactions on protein and antibody substrates with accurate resolution.

Organic Letters, 2018

A general, mild, and versatile synthesis of the challenging α-aryl-β-ketosulfoxonium ylides has b... more A general, mild, and versatile synthesis of the challenging α-aryl-β-ketosulfoxonium ylides has been developed for the first time, substituting traditional methods starting from diazo compounds. The arylation of easily accessible βketosulfoxonium ylides using aryne chemistry allowed the preparation of a large scope of the pro-chiral ylides in very good yields (40 examples; up to 85%). As applications, these ylides were smoothly converted into α-aryl ketones after desulfurization in good yields (up to 98%) as well as in other important derivatives.

The Journal of organic chemistry, Jan 21, 2018

Insertion reactions of diazo carbonyls to azlactones in basic conditions have been performed. The... more Insertion reactions of diazo carbonyls to azlactones in basic conditions have been performed. The developed method allows the preparation of a wide range of oxazole derivatives in yields ranging from 74 to 98%. Different substituents on both azlactone rings and diazo carbonyls do not compromise the methodology, even those containing stereogenic centers. Isotopic labeling experiments revealed the mechanism may proceed through a rare diazo carbonyl activation by an ammonium salt derivative.

European Journal of Organic Chemistry, 2018

Tri‐substituted cyclopentadienes and cyclopentanes, high‐value‐added compounds, are readily prepa... more Tri‐substituted cyclopentadienes and cyclopentanes, high‐value‐added compounds, are readily prepared from ethyl levulinate, a chemical platform easily obtained from biomass. Key steps involve coupling two molecules of ethyl levulinate in the presence of pyrrolidine, followed by a base‐catalyzed intramolecular aldol condensation, to provide a singly‐purified and easily derivatizable cyclopentadiene in almost 40 % isolated overall yield. Reaction conditions are mild, simple and employ green solvents such as ethanol and anisole. This method opens a new pathway to preparing complex molecules from renewable feedstocks.

Chemistry - A European Journal, 2017

A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkylhalides is de... more A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkylhalides is described. The method furnishes several gem-difunctionalized haloketones (an alkyl and F, Cl, Br, or I) in good yields. Replacing alkyhalides with a mixture of electrophilic halogen species and various halide anions led to gemdihalogenated ketones containing a combination of the same or two different halogens. Kinetic isotopic effects as well as reaction kinetic experiments give insight to the mechanism of these reactions. Sulfur ylides were described in 1930 by Ingold and Jessop. 1 Although almost 90 years has passed, most applications involving these compounds are related to the pioneering work developed by Johnson and LaCount, 2 Franzen, 3 and Corey and Chaykovsky 4 in the 1960s. For example, cyclopropanation, epoxidation, and aziridination reactions as well as [2,3] sigmatropic rearrangements are most commonly used. 5 New transformations employing sulfur ylides have been described in more recent years, 5,6 but this has occurred less frequently than expected when compared to other classes of compounds.

Bioorganic & medicinal chemistry letters, Nov 15, 2017

The effects on potency of cruzain inhibition of replacing a nitrile group with alternative warhea... more The effects on potency of cruzain inhibition of replacing a nitrile group with alternative warheads were explored. The oxime was almost an order of magnitude more potent than the corresponding nitrile and has the potential to provide access to the prime side of the catalytic site. Dipeptide aldehydes and azadipeptide nitriles were found to be two orders of magnitude more potent cruzain inhibitors than the corresponding dipeptide nitriles although potency differences were modulated by substitution at P1 and P3. Replacement of the α methylene of a dipeptide aldehyde with cyclopropane led to a loss of potency of almost three orders of magnitude. The vinyl esters and amides that were characterized as reversible inhibitors were less potent than the corresponding nitrile by between one and two orders of magnitude.

Chemical Communications, 2015

The direct conversion of LA, from crude liquors after biomass acid hydrolysis, into GVL is achiev... more The direct conversion of LA, from crude liquors after biomass acid hydrolysis, into GVL is achieved using Fe catalysts.

ACS Sustainable Chemistry & Engineering, 2017

Described are the selectivities observed for reactions of lignin model compounds with modificatio... more Described are the selectivities observed for reactions of lignin model compounds with modifications of the copper-doped porous metal oxide (CuPMO) system previously shown to be a catalyst for lignin disassembly in super-critical methanol (Matson et al, J. Amer. Chem. Soc. 2011, 133, 14090-14097). The models studied are benzyl phenyl ether, 2phenylethyl phenyl ether, diphenyl ether, biphenyl and 2,3 dihydrobenzofuran, which are respective mimetics of the α-O-4, β-O-4, 4-O-5, 5-5 and β-5 linkages characteristic of lignin. Also briefly investigated as a substrate is poplar organosolv lignin. The catalyst modifications included added samarium(III) (both homogeneous and heterogeneous) or formic acid. The highest activity for the hydrogenolysis of aryl ether linkages was noted for catalysts with Sm(III) incorporated into the solid matrix of the PMO structure. In contrast, simply adding Sm 3+ salts to the solution suppressed the hydrogenolysis activity. Added formic acid suppressed aryl ether hydrogenolysis, presumably by neutralizing base sites on the PMO surface but at the same time improved the selectivity toward aromatic products. Acetic acid induced similar reactivity changes. While these materials were variously successful in catalyzing the hydrogenolysis of the different ethers, there was very little activity toward the cleavage of the 5-5 and β-5 CC bonds that represent a small, but significant, percentage of the linkages between monolignol units in lignins..

The Journal of Organic Chemistry, 2016

Proceedings of the 15th Brazilian Meeting on Organic Synthesis Proceedings, 2013

Accounts of chemical research, Jan 19, 2015

Among the different types of diazocarbonyl substrates found in the literature to date, α,β-unsatu... more Among the different types of diazocarbonyl substrates found in the literature to date, α,β-unsaturated diazoketones have proven to be very promising as multifunctional intermediates. Possessing a diazo group, a ketone function and a double bond all together in a single molecule, these compounds constitute versatile building blocks for synthesis. For example, double bond functionalization, followed by intramolecular insertion reactions, can be a short alternative to prepare several rings or heterocyclic compounds. Although there are many efficient methods to prepare diazoketones, very few can be extended to the synthesis of the a,β-unsaturated diazoketones; this is likely responsible for their limited application in synthesis. Unfortunately, the classical methods to prepare saturated- or aryl-diazoketones (acylation of diazomethane with acyl chlorides or mixed anhydrides) are not suitable for preparing a,β-unsaturated diazoketones, since pyrazolines (dipolar cycloaddition products fr...

Proceedings of the 15th Brazilian Meeting on Organic Synthesis Proceedings, 2013

Journal of Molecular Structure: THEOCHEM, 2005

In the last years, Kenji Koga and co-workers [1a], [1b], [1c] and [1d] developed a new methodolog... more In the last years, Kenji Koga and co-workers [1a], [1b], [1c] and [1d] developed a new methodology for the asymmetric synthesis of α,α-dialkyl β-ketoesters in high enantiomeric excess. These ketoesters were prepared via the alkylation of chiral lithium enamines (3) derived from α-alkyl β-...