- Asymmetric Aza-Diels-Alder Reactions of in Situ Generated β,β-Disubstituted α,β-Unsaturated N-H Ketimines Catalyzed by Chiral Phosphoric Acids
-
A novel asymmetric synthesis of dihydropyridinones with vicinal quaternary stereocenters has been realized by asymmetric aza-Diels-Alder reactions of 3-amido allylic alcohols with oxazolones enabled by chiral phosphoric acid catalysis. A series of aryl/alkyl- and alkyl/alkyl-disubstituted 3-amido allylic tertiary alcohols and 4-substituted oxazolones could be well tolerated in these reactions, producing dihydropyridinones with excellent diastereoselectivities and high enantioselectivities. Mechanistic study and control experiments were performed to shed light on the reaction mechanism, in which a configurationally defined β,β-disubstituted α,β-unsaturated N-H ketimine was proposed as the key intermediate.
- He, Shunlong,Gu, Huanchao,He, Yu-Peng,Yang, Xiaoyu
-
supporting information
p. 5633 - 5639
(2020/07/14)
-
- Palladium-catalyzed asymmetric decarboxylative allylation of azlactone enol carbonates: Fast access to enantioenriched α-allyl quaternary amino acids
-
We report a fast protocol for the synthesis of enantioenriched quaternary 4-allyl oxazol-5-ones. The key step is a Pd-catalyzed enantioselective Tsuji allylation of azlactone allyl enol carbonates, which can be easily prepared starting from racemic α-amino acids. The use of (R,R)-DACH-phenyl Trost chiral ligand allowed the attainment of the allylated derivatives in very good yields (83–98 %) and with ee up to 85 %. Scaling up the allylation protocol to gram quantities did not affect the yields end ee values. The produced 4-allyl azlactones can be converted into the corresponding quaternary amino acids or submitted to further synthetic elaborations exploiting the allyl moiety as a handle for the attachment of alkyl and aryl groups. After hydrolysis of the azlactone ring, the zwitterionic amino acids can be attained in enantiopure or nearly optically pure form through only one recrystallization step.
- Serra, Massimo,Bernardi, Eric,Marrubini, Giorgio,De Lorenzi, Ersilia,Colombo, Lino
-
p. 732 - 741
(2019/01/09)
-
- Asymmetric construction of dihydrobenzofuran-2,5-dione derivatives via desymmetrization of p-quinols with azlactones
-
The desymmetrization of p-quinols through a chiral bisguanidinium hemisalt catalyzed enantioselective Michael addition/lactonization cascade reaction with azlactones was reported. 3-Amino-benzofuran-2,5-diones containing a chiral amino acid residue were achieved with up to 99% ee and >19?:?1 dr. An exploration of the structure of the catalyst bisguanidinium was undertaken, revealing a bifunctional catalytic model.
- Xie, Lihua,Dong, Shunxi,Zhang, Qian,Feng, Xiaoming,Liu, Xiaohua
-
supporting information
p. 87 - 90
(2019/01/03)
-
- STRUCTURE AND SYNTHESIS OF HIGHLY FLUORINATED AMINO ACID DERIVATIVES
-
Methods of synthesizing polyfluorinated amino acid derivatives are disclosed, along with polyfluorinated amino acid derivatives produced from said methods, as well as compositions containing same. The synthesis methods utilize an oxazolone and a perfluoroarene to produce the polyfluorinated amino acid derivatives.
- -
-
Paragraph 0170; 0171; 0172; 0175
(2018/09/19)
-
- Metal-Free Insertion Reactions of Diazo Carbonyls to Azlactones
-
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.
- De Mello, Amanda C.,Momo, Patrícia B.,Burtoloso, Antonio C. B.,Amarante, Giovanni W.
-
p. 11399 - 11406
(2018/09/12)
-
- Group-Assisted Purification Chemistry for Asymmetric Mannich-type Reaction of Chiral N-Phosphonyl Imines with Azlactones Leading to Syntheses of α-Quaternary α,β-Diamino Acid Derivatives ?
-
An asymmetric Mannich-type reaction between chiral N-phosphonyl imines and azlactones [oxazol-5(4H)-ones] has been established under convenient conditions at room temperature. The reaction was performed without using any bases, additives, or catalysts to achieve up to excellent chemical yields and diastereoselectivity for 32 examples. The α-quaternary syn-α,β-diamino acid products were purified simply by washing the crude mixtures with cosolvents, following the group-assisted purification chemistry/technology, without involving traditional chromatography or recrystallization methods. The auxiliary can be readily removed and recycled for reuse. The absolute configuration was unambiguously assigned by X-ray structural analysis.
- Zhang, Haowei,Yang, Zhen,Zhao, Brian Nlong,Li, Guigen
-
p. 644 - 655
(2018/01/27)
-
- Polyfluoroarylation of oxazolones: Access to non-natural fluorinated amino acids
-
Herein, conditions are provided for the formation and use of the oxazolone enolate for the nucleophilic substitution of highly fluorinated (hetero)arenes, which after unmasking yield highly fluorinated non-natural amino acids and derivatives. In addition, the properties and chemical behavior of this new class of amino acids are explored. The utility is demonstrated in the one pot synthesis of medicinally relevant 2-aminohydantoins.
- Teegardin, Kip A.,Weaver, Jimmie D.
-
supporting information
p. 4771 - 4774
(2017/07/06)
-
- Enantioselective synthesis of dihydrocoumarin derivatives by chiral scandium(iii)-complex catalyzed inverse-electron-demand hetero-Diels-Alder reaction
-
An asymmetric inverse-electron-demand hetero-Diels-Alder reaction between o-quinone methides and azlactones to generate potentially pharmacological active dihydrocoumarins has been achieved efficiently by using a chiral N,N′-dioxide-Sc(iii) complex as the catalyst. The desired products were obtained in high yields with excellent enantioselectivities and diastereoselectivities (up to 94% yield, 96% ee and >19:1 dr) under mild reaction conditions. A concerted reaction pathway was confirmed by Operando IR and control experiments.
- Hu, Haipeng,Liu, Yangbin,Guo, Jing,Lin, Lili,Xu, Yali,Liu, Xiaohua,Feng, Xiaoming
-
supporting information
p. 3835 - 3837
(2015/03/31)
-
- Alkynyliodonium salt mediated alkynylation of azlactones: Fast access to Cα-tetrasubstituted α-amino acid derivatives
-
An efficient electrophilic alkynylation of azlactones (oxazol-5(4H)-ones) is developed using alkynyl(phenyl)iodonium salts as the electrophilic alkyne source. After remarkably short reaction times, the desired alkyne functionalized azlactones are obtained in 60-97% yield and can be transformed easily into a variety of quaternary α-amino acid derivatives.
- Finkbeiner, Peter,Weckenmann, Nicole M.,Nachtsheim, Boris J.
-
supporting information
p. 1326 - 1329
(2014/04/03)
-
- Organocatalyzed asymmetric 1,4-addition of azlactones to α,β-unsaturated trichloromethyl ketones: Synthesis of α,α-disubstituted α-amino acid derivatives
-
The first asymmetric 1,4-addition of azlactones to α,β-unsaturated trichloromethyl ketones catalyzed by cinchona alkaloid derived bifunctional thiourea catalysts was developed. A series of α,α-disubstituted α-amino acid derivatives bearing a quaternary stereocenter at the α-position were obtained in high yields with excellent diastereo- and enantioselectivities (up to -20:1 dr and 99% ee). In addition, the trichloromethyl moiety in these adducts was identified as a good leaving group.
- Zhang, Jinlong,Liu, Xihong,Wu, Chongyang,Zhang, Panpan,Chen, Jianbo,Wang, Rui
-
supporting information
p. 7104 - 7108
(2015/01/16)
-
- One-pot preparation of oxazol-5(4H)-ones from amino acids in aqueous solvents
-
A method for one-pot synthesis of oxazol-5(4H)-ones has been developed using 4-(4,6-dimethoxy-l,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM), which is available for the activation of carboxylic acids in an aqueous solvent. The oxazolones were prepared by the TV-acylation of amino acids with carboxylic acids and the subsequent cyclodehydration of the resulting N-acylamino acids by the addition of N,N-diethylaniline. Since both these reactions proceed effectively with the same coupling reagent, DMT-MM, in aqueous solvents, the procedure is simplified and becomes easy to perform. In addition, 5-(triazinyloxy)oxazole derivatives have been synthesized by controlling the basicity of the reaction system.
- Fujita, Hikaru,Kunishima, Munetaka
-
p. 907 - 912
(2012/08/08)
-
- Polyclonal antibodies: A cheap and efficient tool for screening of enantioselective catalysts
-
Enantioselective polyclonal antibodies have been produced and characterized to develop a high-throughput screening method for lipase activity fingerprinting, with a view to the enantioselective hydrolysis of azlactones.
- MacOvei, Cristian,Vicennati, Paola,Quinton, Julia,Nevers, Marie-Claire,Volland, Herve,Creminon, Christophe,Taran, Frederic
-
supporting information; experimental part
p. 4411 - 4413
(2012/05/20)
-
- Asymmetric synthesis of 3, 4-diaminochroman-2-ones promoted by guanidine and bisguanidium salt
-
A highly enantioselective synthesis of 3,4-diaminochroman-2-ones has been realized via the domino reaction of o-hydroxy aromatic aldimines and azlactones. Notably, a cis-product was obtained as the major product by the use of guanidine 2a whereas a trans-product was the major product with bisguanidium salt 3·HBArF 4. In two cases, various substituted 3,4-dihydrocoumarins were obtained with high yields (up to 99%) as well as excellent enantioselectivities (up to 99% ee) and diastereoselectivities (up to >99:1 cis:trans and 98:2 trans:cis, respectively) under mild reaction conditions.
- Dong, Shunxi,Liu, Xiaohua,Zhang, Yulong,Lin, Lili,Feng, Xiaoming
-
supporting information; experimental part
p. 5060 - 5063
(2011/12/05)
-
- AN EFFICIENT TRANSFORMATION OF N-ACYL-α-AMINO ACIDS INTO DIACYLAMINES VIA 2,4-DISUBSTITUTED OXAZOL-5(4H)-ONES
-
Base-catalyzed oxygenative decarboxylation of a variety of 2,4-disubstituted oxazol-5(4H)-ones in benzene with triethylamine or in dimethylsulfoxide with potassium tert-butoxide gives diacylamines.KEYWORDS - base-catalyzed autooxidation; selective oxygenation; decarboxylation; oxazol-5(4H)-one; N-acyl-α-amino acid; diacylamine
- Suda, Kohji,Hino, Fumio,Yijima, Chino
-
p. 882 - 885
(2007/10/02)
-