Alicia Boto, Rosendo Hernández, Ernesto Suárez, Carmen Betancor, Mariá S. Rodríguez,
... New Synthesis of Steroidal .beta.-Peroxy LactonesAlicia Boto, Rosendo Hernandez, Ernesto Suarez, Carmen Betancor, and Maria S. RodriguezCite ...
Tópico(s): Steroid Chemistry and Biochemistry
1995 - American Chemical Society | The Journal of Organic Chemistry
Carmen Betancor, J. I. CONCEPCION, Rosendo Hernández, José A. Salazar, Ernesto Suárez,
... 1,4-epimine compoundsCarmen Betancor, Jose I. Concepcion, Rosendo Hernandez, Jose A. Salazar, and Ernesto SuarezCite this: J. ...
Tópico(s): Advanced Synthetic Organic Chemistry
1983 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández,
Abstract Common amino acid derivatives can be transformed in one‐step fashion into N ‐azanucleosides. The method is a sequential process initiated by a domino radical decarboxylation/oxidation reaction; an acyliminium ion is formed as an intermediate and can be trapped by nitrogen bases (purines, pyrimidines, and benzotriazole). The mildness of the reaction conditions and the good yields obtained make this procedure an interesting alternative to the conventional processes. Good stereoselectivities ...
Tópico(s): Catalytic C–H Functionalization Methods
2010 - Wiley | European Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández,
An alternative to the use of expensive auxiliaries or catalysts in the synthesis of chiral 2-substituted pyrrolidines is described. Thus, commercial, cheap 4-(S)-hydroxyproline was readily transformed into optically pure pyrrolidines, using a one-pot decarboxylation–alkylation reaction as the key step. In this reaction, an acyliminium intermediate was generated, which was trapped by carbon nucleophiles. As postulated by Woerpel, the addition of the nucleophiles to the five-membered ring iminium ...
Tópico(s): Marine Sponges and Natural Products
2009 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Dácil Hernández, Rosendo Hernández,
Common sugar derivatives can be transformed in a few steps into chiral-substituted furyl carbinols. The mildness of the reaction conditions and the good yields obtained make this procedure an interesting alternative to the conventional processes.
Tópico(s): Synthesis of Indole Derivatives
2007 - American Chemical Society | Organic Letters
Alicia Boto, Dácil Hernández, Rosendo Hernández, Eleuterio Álvarez,
The design of processes which combine tandem and sequential reactions allows the transformation of readily available precursors into high-profit products. This strategy is illustrated by the one-pot synthesis of acyclic nucleosides, which are potential antiviral compounds, from readily available carbohydrates. The reaction conditions are mild, compatible with most functional groups. Depending on the starting sugar, both common and uncommon acyclic chains can be prepared. These polyhydroxylated chains ...
Tópico(s): HIV/AIDS drug development and treatment
2007 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Juan Antonio Gallardo, Dácil Hernández, Rosendo Hernández,
The fragmentation of primary alkoxyl radicals has been scarcely used in synthesis since other competing processes (such as oxidation or hydrogen abstraction) usually predominate. However, when serine derivatives were used as substrates, the scission took place in excellent yields. Tandem scission−allylation, −alkylation, or −arylation reactions were subsequently developed. This one-pot methodology was applied to the synthesis of unnatural amino acids, which are useful synthetic blocks or amino acid ...
Tópico(s): Click Chemistry and Applications
2007 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández, Ernesto Suárez,
The selective cleavage of methoxy protecting groups next to hydroxy groups is achieved using a radical hydrogen abstraction reaction as the key step. Under the reaction conditions, the hydroxy group generates an alkoxyl radical that reacts with the sterically accessible adjacent methoxy group, which is transformed into an acetal. In the second step, the acetals are hydrolyzed to give alcohols or diols. A one-pot hydrogen abstraction−hydrolysis procedure was also developed. Good yields were usually ...
Tópico(s): Enzyme Catalysis and Immobilization
2006 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández, Adriana Montoya, Ernesto Suárez,
Abstract The fragmentation of primary alkoxyl radicals is usually a minor process with respect to hydrogen abstraction and other competing reactions. However, when β‐amino alcohols were used as substrates, the scission proceeded in good to excellent yields and no side reactions were observed. The fragmentation can be coupled with an allylation or alkylation reaction, to give alkaloid analogues and functionalized nitrogen heterocycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Tópico(s): Asymmetric Synthesis and Catalysis
2006 - Wiley | European Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández, Ernesto Suárez,
[reaction: see text] The selective removal from carbohydrate substrates of methoxy protecting groups next to hydroxy groups is reported. On treatment with PhI(OAc)(2)-I(2), the methoxy group is transformed into an easily removable acetal. The mild conditions of this methodology are compatible with many functional groups, and good to excellent yields are usually achieved.
Tópico(s): Chemical Synthesis and Reactions
2004 - American Chemical Society | Organic Letters
Alicia Boto, Dácil Hernández, Rosendo Hernández, Ernesto Suárez,
The β-fragmentation of primary alkoxyl radicals, described in many cases as low-yielding and plagued by side reactions, can proceed in satisfactory yields using carbohydrate substrates. The only reaction that can compete significantly with the β-scission is the intramolecular hydrogen abstraction. The ratio of β-fragmentation to hydrogen abstraction can be varied according to the reaction conditions, the stereochemistry of the substituents (e.g., α- or β-anomeric substituents), and the protecting ...
Tópico(s): Enzyme Catalysis and Immobilization
2003 - American Chemical Society | The Journal of Organic Chemistry
R. Hernández, José Rosendo Hernández-Reséndiz, Luis Alejandro Martínez-Chávez, Rodrigo Velázquez-Castillo, L. Escobar‐Alarcón, Karen Esquivel,
Tópico(s): Pigment Synthesis and Properties
2020 - Springer Science+Business Media | Journal of Sol-Gel Science and Technology
R. Hernández, José Rosendo Hernández-Reséndiz, Marisela Cruz-Ramírez, Rodrigo Velázquez-Castillo, L. Escobar‐Alarcón, Luis Ortiz‐Frade, Karen Esquivel,
Titanium dioxide (TiO2) is a widely used and well studied photocatalyst synthesized using different methodologies, including sol-gel, which allows one to modify the material in a one-pot step. By using a microwave- and sonochemistry-assisted sol-gel method, x wt.% Au-TiO2 photocatalysts were successfully synthesized. Physicochemical characterization of the photocatalysts shows an average crystallite size of 10.5 nm and an even morphological distribution of spherical particles with the sonochemistry ...
Tópico(s): Advanced Nanomaterials in Catalysis
2020 - Multidisciplinary Digital Publishing Institute | Catalysts
Alicia Boto, Dácil Hernández, Rosendo Hernández,
Readily available sugar derivatives were transformed in a few steps into valuable, more complex products. The tandem radical scission of carbohydrates−oxidation reaction gave acetoxy acetals, which were converted into a variety of chiral C-alditols in good global yields and excellent 1,2-trans stereoselectivity. The reaction was the key step in the synthesis of hydroxylated γ-substituted butenolides and bicyclic alkaloid analogues.
Tópico(s): Microbial Natural Products and Biosynthesis
2008 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Dácil Hernández, Rosendo Hernández,
Common cyclic amino acids, derived from proline and hydroxyproline, can be readily transformed into azanucleosides. The mildness of the reaction conditions, and the good yields obtained, make this procedure an interesting alternative to the conventional processes.
Tópico(s): DNA and Nucleic Acid Chemistry
2007 - Elsevier BV | Tetrahedron Letters
Carlos J. Saavedra, Alicia Boto, Rosendo Hernández, José I. Miranda, J. M. Aizpurua,
Short α,β,α-tripeptides comprising a central chiral trisubstituted β2,2,3*-amino acid residue form unusual γ-turns and δ-turns in CDCl3 and DMSO-d6 solutions but do not form β-turns. Thermal coefficients of backbone amide protons, 2D-NMR spectra, and molecular modeling revealed that these motifs were strongly dependent on the configuration (chiral effect) of the central β-amino acid residue within the triad. Accordingly, SSS tripeptides adopted an intraresidual γ-turn like (C6) arrangement in the ...
Tópico(s): Glycosylation and Glycoproteins Research
2012 - American Chemical Society | The Journal of Organic Chemistry
Carlos J. Saavedra, Alicia Boto, Rosendo Hernández,
The site-selective modification of small peptides at a glutamate residue allows the ready preparation of α,γ-hybrids. In this way, a single peptide can be transformed into a variety of hybrid derivatives. The process takes place under very mild conditions, and good global yields are obtained.
Tópico(s): Carbohydrate Chemistry and Synthesis
2012 - American Chemical Society | Organic Letters
Carlos J. Saavedra, Alicia Boto, Rosendo Hernández,
The selective conversion of serine or threonine units of di- and tripeptides into substituted dehydroamino acids is reported. Thus, these common α-amino acids undergo a scission–phosphorylation process to give α-amino phosphonate residues. A Horner–Wadsworth–Emmons reaction with aldehydes or ketones follows to afford the final products with excellent Z-stereoselectivity (Z:E > 98:2). In this way, a single peptide precursor can selectively be transformed into a variety of derivatives.
Tópico(s): Click Chemistry and Applications
2012 - American Chemical Society | Organic Letters
Carlos J. Saavedra, Rosendo Hernández, Alicia Boto, Eleuterio Álvarez,
The one-pot conversion of readily available α-amino acid into β-amino acid derivatives was carried out in good yields. The method is a sequential process initiated by a tandem radical decarboxylation−oxidation reaction; the resulting acyliminium ion was trapped by silyl ketenes. Stoichiometric and catalytic versions of this reaction were developed and then applied to prepare modified di- and tripeptides. Interestingly, some tripeptides formed expanded β-turns in the solid state.
Tópico(s): Carbohydrate Chemistry and Synthesis
2009 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Juan Antonio Gallardo, Rosendo Hernández, Carlos J. Saavedra,
The one-pot radical fragmentation–phosphorylation reaction of α-amino acids and β-amino alcohols affords α-amino phosphonates in good yields. The reaction was applied to the synthesis of potentially bioactive phosphonates.
Tópico(s): Chemical Synthesis and Analysis
2005 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Rosendo Hernández, Yolanda de León, José Ramón Murguía, Abigail Rodrı́guez-Afonso,
Abstract Iodinated or oxygenated nitrogen heterocycles are obtained by radical decarboxylation of β‐ and γ‐amino acids. This mild, versatile reaction is applied to the synthesis of bioactive products, such as 4‐arylpiperidines, hydroxylated piperidines, and new antifungal agents.
Tópico(s): Catalytic C–H Functionalization Methods
2005 - Wiley | European Journal of Organic Chemistry
Alicia Boto, Yolanda de León, Juan Antonio Gallardo, Rosendo Hernández,
Abstract A mild, one‐pot methodology to obtain α‐substituted nitrogen heterocycles from commercial amino acids is reported. This versatile procedure has been applied to the synthesis of different alkaloid analogues in good to excellent yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Tópico(s): Asymmetric Synthesis and Catalysis
2005 - Wiley | European Journal of Organic Chemistry
Rosendo Hernández, Elisa I. León, Pilar Moreno, Concepción Riesco‐Fagundo, Ernesto Suárez,
The synthesis of highly functionalized nitriles by an alkoxyl radical fragmentation of cyclic beta-hydroxy azides is described. The alkoxyl radicals were generated by reaction of the alcohols with (diacetoxyiodo)benzene and iodine under mild conditions compatible with the presence of sensitive substituents and the protective groups most frequently used in carbohydrate chemistry. To explore the scope and limitations of this methodology, experiments were carried out using a variety of beta-hydroxy ...
Tópico(s): Synthesis and Biological Evaluation
2004 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Rosendo Hernández, Adriana Montoya, Ernesto Suárez,
Tópico(s): Radical Photochemical Reactions
2004 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Rosendo Hernández, Adriana Montoya, Ernesto Suárez,
A mild and highly efficient one-pot synthesis of aryl glycines from easily available serine derivatives is described. This methodology is also applied to the synthesis of other uncommon amino acids.
Tópico(s): Asymmetric Synthesis and Catalysis
2002 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Rosendo Hernández, Yolanda de León, Ernesto Suárez,
A new synthesis of 2,3-disubstituted pyrrolidines and piperidines is described. This mild procedure is based on the one-pot oxidative decarboxylation−β-iodination of α-amino acid carbamates or amides. The iodine is introduced at the previously unfunctionalized 3-position. Different substituents can be introduced at C-2, e.g., hydroxy, alkoxy, allyl, alkyl, etc. A trans relationship between the C-2 and C-3 substituents is exclusively obtained. The influence of the solvent and the ring size of the ...
Tópico(s): Chemical Synthesis and Analysis
2001 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Rosendo Hernández, Ernesto Suárez,
A convenient methodology for the synthesis of 2-substituted pyrrolidines from α-amino acids is described. A number of cyclic and acyclic α-amino acid derivatives have been prepared in order to test the scope and diastereoselectivity of this method. These substrates were treated with iodosylbenzene or (diacetoxyiodo)benzene (DIB) and iodine in order to generate the corresponding carboxyl radical, which evolves by loss of carbon dioxide to produce a carbon radical which in turn undergoes oxidation to ...
Tópico(s): Catalytic C–H Functionalization Methods
2000 - American Chemical Society | The Journal of Organic Chemistry
Alicia Boto, Rosendo Hernández, Ernesto Suárez,
A mild and efficient procedure for the tandem decarboxylation-halogenation of α-amino acids is reported. The iodine is introduced at previously unfunctionalized positions, in good yields. The methodology has been used for the diastereoselective synthesis of 2,3-disubstituted pyrrolidines.
Tópico(s): Synthetic Organic Chemistry Methods
2000 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Rosendo Hernández, Ernesto Suárez,
Tópico(s): Alkaloids: synthesis and pharmacology
2000 - Elsevier BV | Tetrahedron Letters
Alicia Boto, Rosendo Hernández, S. M. VELAZQUEZ, Ernesto Suárez, T. Prangé,
A new one-pot synthesis of 3,5-substituted 1,2-dioxolanes from six-membered cyclic peroxyhemiacetal derivatives of hexahydrobenzo[c][1,2]dioxin-8a-ol is described. A number of steroidal peroxyhemiacetals, (2S,2'S,3R)-(11), (2S,2'R,3R/S)-(13), (2R,2'R,3R/S)-2-(2'-hydroperoxypropyl-3'-phenylsulfonyl)-5α-cholestan-3-one 2',3-peroxyhemiacetal (17), and (2S,5R)-2-hydroperoxy-3-phenylsulfonyl-4-nor-3,4-secocholestan-5-one 2,5-peroxyhemiacetal (24), have been prepared in order to test the scope and diastereoselectivity ...
Tópico(s): Radical Photochemical Reactions
1998 - American Chemical Society | The Journal of Organic Chemistry