84312-20-9Relevant academic research and scientific papers
C- and N-Selective Grignard Addition Reactions of α-Aldimino Esters in the Presence or Absence of Zinc(II) Chloride: Synthetic Applications to Optically Active Azacycles
Hatano, Manabu,Yamashita, Kenji,Ishihara, Kazuaki
, p. 2412 - 2415 (2015/05/27)
Highly practical synthetic methods were developed for the C- and N-selective Grignard addition reactions of N-4-MeOC6H4-protected α-aldimino esters in the presence or absence of zinc(II) chloride. Diastereoselective C-alkyl addition, tandem C-alkyl addition-N-alkylation, and some transformations to synthetically useful optically active azacycles were demonstrated. (Chemical Equation Presented).
The origin of stereoselectivity in cycloaddition reactions promoted by stereoisomers of 8-phenylmenthyl glyoxylate oxime
Sousa, Carlos A.D.,Lima, Carlos F.R.A.C.,Andrade, Mariana,García-Mera, Xerardo,Rodriguez-Borges, José E.
, p. 5048 - 5057 (2013/07/04)
A structural study of three synthesized stereoisomeric oximes, (-)-8-phenylmenthyl glyoxylate oxime (8-PMGO), (+)-8-phenylneomenthyl glyoxylate oxime (8-PnMGO), and (-)-8-phenylisoneomenthyl glyoxylate oxime (8-PinMGO), was performed by means of variable temperature 1H NMR spectroscopy, X-ray crystallography, and ab initio calculations. It was found that in 8-PMGO a conformation where the phenyl and oxime moieties are stacked is significantly favored, whereas in the other stereoisomers this preference was not so evident. The conformational differences found between the isomers were used to rationalize the outcome of the reaction (simultaneous 1,3-cycloaddition and aza-Diels-Alder reaction) between the referred oximes and cyclopentadiene, in which the stereoselectivity was evaluated and found to be nicely reproduced by a simple conformational analysis. The global results indicate that the stereoselectivity of the studied oximes, a bit higher for 8-PMGO, originates from their particular conformational distribution, in which the phenyloxime aromatic interaction plays a decisive role.
Highly stereoselective cycloadditions of Danishefsky's diene to (-)-8-phenylmenthyl and (+)-8-phenylneomenthyl glyoxylate N-phenylethylimines
García-Mera, Xerardo,Alves, Maria J.,Goth, Albertino,Do Vale, Maria Luísa,Rodríguez-Borges, José E.
, p. 2909 - 2919 (2013/04/10)
Enantiopure 4-oxo-pipecolic acid derivatives were obtained by double asymmetric induction aza-Diels-Alder reactions between chiral glyoxylate N-phenylethylimines and Danishefsky's diene mediated by zinc iodide. The key to success was the use of iminoacetates possessing two chiral auxiliaries, N-(S)- or N-(R)-1-phenylethyl and (-)-8-phenylmenthyl or (+)-8-phenylneomenthyl. Adducts were formed in good yields (78-81%), with complete regioselectivity and high diastereoselectivity (87-96%). The absolute configuration of the adducts formed was unequivocally assigned through NMR, specific optical rotation and X-ray data of appropriated derivatives. These cycloadducts can serve as precursors for bioactive piperidinic azasugars and pipecolic acid derivatives.
Highly diastereoselective synthesis of 2-azabicyclo[2.2.1]hept-5-ene derivatives: Bronsted acid catalyzed aza-Diels-Alder reaction between cyclopentadiene and imino-acetates with two chiral auxiliaries
Garcia-Mera, Xerardo,Rodriguez-Borges, Jose E.,Vale, M. Luisa C.,Alves, Maria J.
experimental part, p. 7162 - 7172 (2011/10/05)
The cycloaddition between protonated glyoxylate imines possessing two chiral auxiliaries, N-(S)- or N-(R)-1-phenylethyl and (-)-8-phenylmenthyl or (+)-8-phenylneomenthyl, and cyclopentadiene is described. The absolute configuration of all adducts formed was unequivocally assigned through NMR, specific optical rotation, and X-ray data of appropriated derivatives. Experimental results confirm the highly exo-selectivity for these aza-Diels-Alder reactions, single adducts being obtained from combinations of (8PM)-(R-PEA) and (8PNM)-(S-PEA).
The use of (-)-8-phenylisoneomenthol and (-)-8-phenylmenthol in the enantioselective synthesis of 3-functionalized 2-azabicyclo[2.2.1]heptane derivatives via aza-Diels-Alder reaction
Cardoso do Vale, Maria Luísa,Rodríguez-Borges, José Enrique,Caama?o, Olga,Fernández, Franco,García-Mera, Xerardo
, p. 9475 - 9482 (2007/10/03)
The asymmetric aza-Diels-Alder reaction of the (1R)-8-phenylmenthyl or (1R)-8-phenylisoneomenthyl glyoxylate-derived N-benzylimine with cyclopentadiene resulted in the enantioselective synthesis of the corresponding pure [(1S,3-exo)-2-benzyl-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylates (80 or 69% yield, respectively). Reduction of these cycloadducts with LiAlH4 afforded pure (-)-[(1S,3-exo)-2-benzyl-2-azabicyclo[2.2.1]hept-5-en-3-yl]methanol. Furthermore, a reaction sequence based on Barbier-Wieland degradation of both (1S,3-exo)-adducts afforded pure (+)-(1R)-2-benzoyl-2-azabicyclo[2.2.1]heptan-3-one. In the course of the two transformation sequences referred, the chiral auxiliaries were recovered in a virtually quantitative way.
Highly diastereoselective Friedel-Crafts reaction of furans with 8-phenylmenthyl glyoxylate
Kwiatkowski, Piotr,Majer, Jakub,Chaladaj, Wojciech,Jurczak, Janusz
, p. 5045 - 5048 (2007/10/03)
(Chemical Equation Presented) The Friedel-Crafts reaction of (1R)-8-phenylmenthyl glyoxylate with variously substituted furans was found to be efficiently promoted by SnCl4 or magnesium salts with high diastereoselectivities. MgBr2 performs especially well under simple, undemanding conditions, giving both high yields and high diastereoselectivities (>90%). The reaction afforded chiral substituted furan-2-yl-hydroxyacetic acid esters, compounds of potentially high synthetic interest.
Synthesis and X-ray crystal structure of (-)-calicheamicinone
Clive, Derrick L. J.,Bo, Yunxin,Selvakumar, Natesan,McDonald, Robert,Santarsiero, Bernard D.
, p. 3277 - 3290 (2007/10/03)
Diels-Alder reaction between ketene acetal 3 and the β-nitroacrylate ester 12 of (-)-8-phenylmenthol gave optically pure ketone 17. This substance was modified in such a way as to remove the chiral auxiliary and afford the epimeric silyl ethers 20M and 20m. Following procedures worked out using racemic materials, both 20M and 20m were converted into optically pure (-)- calicheamicinone (1). This is a crystalline substance, and an X-ray structure determination was carried out.
An efficient method for preparation of chiral arylmenthol glyoxylates
Blanco, Jose M.,Caamano, Olga,Fernandez, Franco,Garcia-Mera, Xerardo,Lopez, Carmen,Rodriguez-Borges, Jose E.,Hergueta, Antonio R.
, p. 1590 - 1592 (2007/10/03)
Glyoxylates of three chiral alcohols were conveniently prepared by reaction of the alcohol with oxalyl chloride followed by reduction of the resulting alkoxy oxalyl chloride with tributyl- tin hydride. The products were isolated in 75-80% yield by straightforward flash chromatography.
Formal synthesis of (-)-calicheamicinone and of (+)-calicheamicinone
Clive, Derrick L. J.,Selvakumar, Natesan
, p. 2543 - 2544 (2007/10/03)
An asymmetric Diels-Alder reaction between ketene acetal 2 and the 3-nitropropenoate 10, derived from (-)-8-phenyl-menthol, affords the optically pure adduct 15, which can be converted into either enantiomer of calicheamicinone 1.
Highly Enantioselective Synthesis of Pipecolic Acid Derivatives via an Asymmetric Aza-Diels-Alder Reaction
Bailey, Patrick D.,Londesbrough, Derek J.,Hancox, Timothy C.,Heffernan, John D.,Holmes, Andrew B.
, p. 2543 - 2544 (2007/10/02)
Very high asymmetric induction is observed in the aza-Diels-Alder reaction between dienes and the imine (R)-PhMeCH-N=CHCO2PhMen* (where PhMen* = 8-phenylmenthyl), which bears matched auxiliaries on nitrogen and on the ester; reactions in trifluoroethanol, in the presence of trifluoroacetic acid (1 equiv.), give substituted pipecolic acid derivatives in ca 50percent isolated yield, with only a single regio- and diastereo-isomer of the cycloadduct detectable in all cases (d.e. > 95percent).
