Tomás Tejero | University of Zaragoza (original) (raw)

Papers by Tomás Tejero

The Journal of organic chemistry, 2015

The mechanism of the reaction between nitrones and lithium ynolates has been studied using DFT me... more The mechanism of the reaction between nitrones and lithium ynolates has been studied using DFT methods at the M06-2X/cc-pVTZ/PCM=THF level. After the formation of a starting complex an without energy barrier, in which the lithium atom is coordinated to both nitrone and ynolate, the reaction takes place in one single kinetic step through a single transition structure. However, the formation of C-C and C-O bonds takes place sequentially through a typical two-stage, one-step process. A combined study of noncovalent interactions (NCIs) and electron localization function (ELFs) of selected points along the intrinsic reaction coordinate (IRC) of the reaction confirmed that, in the transition structure, only the C-C bond is being formed to some extent, whereas an electrostatic interaction is present between carbon and oxygen atoms previous to the formation of the C-O bond. Indeed, the formation of the second C-O bond only begins when the first C-C bond is completely formed without formatio...

Chemistry-a European Journal, 1995

Letters in Organic Chemistry, 2005

The enantioselectivity of the titanium (IV)-BINOL catalyzed asymmetric Mannich-type reactions of ... more The enantioselectivity of the titanium (IV)-BINOL catalyzed asymmetric Mannich-type reactions of nitrones can be enhanced by using additional chiral ligands. The best results are obtained with diols derived from D-mannitol.

Tetrahedron Letters, 1997

A straightforward synthesis of 2,3-diaminobutanoic acids is reported. The synthesis is based on t... more A straightforward synthesis of 2,3-diaminobutanoic acids is reported. The synthesis is based on the nucleophilic addition of methylmagnesium bromide to differentially protected nitrones derived from l-serine. The change of the protecting groups in the starting nitrone is crucial for the stereocontrol of the reaction.

Tetrahedron-asymmetry, 1997

The stereoselective addition of Grignard reagents to α-alkoxy nitrones has been achieved with exc... more The stereoselective addition of Grignard reagents to α-alkoxy nitrones has been achieved with excellent stereocontrol using ZnBr2 and Et2AlCl as precomplexing agents to obtain the corresponding syn- and anti- adducts, respectively. The obtained hydroxylamines have been transformed into valuable 3-amino-1,2-diols.

Chemical Communications, 1998

Tetrahedron-asymmetry, 1998

The asymmetric synthesis of protected (2R,3S)- and (2R,3R)-3-substituted 2,3-α-amino acids is rep... more The asymmetric synthesis of protected (2R,3S)- and (2R,3R)-3-substituted 2,3-α-amino acids is reported. The key step in the synthesis of these compounds is the diastereoselective addition of Grignard reagents to α-amino nitrones derived from l-serine. Total stereocontrol of the addition step is achieved by changing the protecting groups in the starting material. The predominant selectivity in each case can be reasonably

Journal of Organic Chemistry, 2000

Blot, J.; Bellec, C.; Fargeau-Bellassoued, M. C.; Haviari, G.; Célérier, J.-P.; Lhommet, G.; Gram... more Blot, J.; Bellec, C.; Fargeau-Bellassoued, M. C.; Haviari, G.; Célérier, J.-P.; Lhommet, G.; Gramain, J.-C.; Gardette, D. van der Deen, H.; Cuiper, A. D.; Hof, R. P.; van Oeveren, A.; Feringa, B. L.; Kellogg, R. M. Muller, R.; Leibold, T.; Hein, M.; Schwarz, M.; Fengler, M.; Jaroskova, L.; Patzel, M.; Leroy, P.-Y. Bull. Soc. Chim. Belg. 1994, 103, 491-507. (3) (a) Takebayashi, M.; Hiranuma, S.; Kanie, Y.; Kajimoto, T.; Kanie, O.; Wong, C.-H.

Tetrahedron-Asymmetry, 2000

A synthetic approach to l-isoxazolidinyl nucleosides is demonstrated by the stereoselective conve... more A synthetic approach to l-isoxazolidinyl nucleosides is demonstrated by the stereoselective conversion of N-benzyl-1,2-di-O-isopropylidene-d-glyceraldehyde nitrone (BIGN) into cis and trans l-isoxazolidinyl thymidine. The methodology consists of the 1,3-dipolar cycloaddition of BIGN with either vinyl acetate or a vinyl base to give key intermediates that are easily transformed into the target compound. The experimental results of the cycloaddition reactions can be qualitatively explained by theoretical ab initio calculations. #

Molecules, 2001

The ZnBr2 complex of the title compound has been studied by both structural and theoretical metho... more The ZnBr2 complex of the title compound has been studied by both structural and theoretical methods. Similar reactivities have been observed for the nitrone alone and the complex in 1,3-dipolar cycloadditions and nucleophilic additions.

ChemInform, 2010

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.

Tetrahedron: Asymmetry, 2007

We have recently reported on our successful efforts to develop general routes to isoxazolidinyl n... more We have recently reported on our successful efforts to develop general routes to isoxazolidinyl nucleosides, 8 a new class of nucleoside analogues in which the furanose ring has been replaced by an isoxazolidine ring. 9 Our synthetic strategy may now be applicable to the synthesis ...

Tetrahedron: Asymmetry, 1995

Tetrahedron: Asymmetry, 2002

The 1,3-dipolar cycloaddition reactions of five D-glyceraldehyde nitrones with alkyl acrylates an... more The 1,3-dipolar cycloaddition reactions of five D-glyceraldehyde nitrones with alkyl acrylates and Oppolzer's sultam acrylamide have been studied in detail, the study including double chiral induction experiments. A complete theoretical study of the reaction has also been carried out using density functional methods (B3LYP/6-31G*) in which both ortho and meta channels leading to 3,5-and 3,4-disubstituted isoxazolidines, respectively, were considered. The adducts obtained from the cycloaddition reactions have been further used for the stereoselective synthesis of protected 4-hydroxy pyroglutamic acids, particularly the (2S,4S)-isomer, which is prepared from the major adducts of the cycloaddition reactions.

Tetrahedron Letters, 2006

Epimeric pyrrolidinyl glycines, a sort of conformationally constrained a,b-diaminoacids, were ste... more Epimeric pyrrolidinyl glycines, a sort of conformationally constrained a,b-diaminoacids, were stereoselectively prepared using complementary approaches based on nitrone chemistry. Nucleophilic additions to pyrrolidinyl nitrones and 1,3-dipolar cycloadditions of L L-serine derived nitrones to form the corresponding hydroxylamines and isoxazolidines, respectively, provided key intermediates for the synthesis of the target compounds. Whereas the nucleophilic addition route afforded the syn adduct, the 1,3-dipolar cycloaddition approach furnished the precursor for the preparation of the corresponding anti compound.

Tetrahedron, 2012

A new straightforward route to glycomimetics containing a piperidine unit is reported. The key st... more A new straightforward route to glycomimetics containing a piperidine unit is reported. The key step of the methodology is the intramolecular 1,3-dipolar cycloaddition of easily accessible glycosyl alkenyl nitrones. The reaction takes place in most cases with a complete selectivity in favor of the exoeexo adduct, which facilitates the synthesis of all-cis piperidines bearing the glycosyl units. The direct transformation of adducts into the final imino-C-di and trisaccharide analogues is achieved in one step using simple reagents. Inhibition properties against two glycosidases have been tested but no positive results have been found.

Tetrahedron, 2001

AbstractÐThe nucleophilic addition of methyl magnesium bromide to a C-(2-pyrrolidinyl) nitrone ha... more AbstractÐThe nucleophilic addition of methyl magnesium bromide to a C-(2-pyrrolidinyl) nitrone has been studied by ab initio molecular orbital (HF/6-311G p ) and density functional theory (B3LYP/6-311G p //HF/6-311G p ) calculations via location of the two diastereomeric transition states. The overall reaction is exothermic and proceeds via precomplexation of the nitrone with the organometallic reagent. The calculations con®rm that chelation is the main factor governing the experimentally con®rmed preference for the Si attack leading to syn adducts. q

Tetrahedron, 1997

The 1,3-dipolar cycloaddition of thiazolyl nitrones with chiral acrylates has been studied. The u... more The 1,3-dipolar cycloaddition of thiazolyl nitrones with chiral acrylates has been studied. The use of the Oppolzer's camphor sultam as chiral inductor provided isoxazolidines with excellent regio-and diastereoselectivities and good asymmetric induction. The cycloadducts were converted into homochiral cc-amino-2-alkylthiazoles and 5-(2-thiazolyl)-3-hydroxy-2-pyrrolidinones. The latter compounds were precursors of highly functionalized pyrrolidines by the aldehyde unmasking from the thiazole ring and subsequent reactions of the formyl group. © 1997 Elsevier Science Ltd. All rights reserved.