- Organocatalytic asymmetric [4+2] cyclization of 2-benzothiazolimines with azlactones: Access to chiral benzothiazolopyrimidine derivatives
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An organocatalytic asymmetric domino Mannich/cyclization reaction between 2-benzothiazolimines with azlactones has been successfully developed. With the bifunctional squaramide catalyst, this formal [4+2] cyclization occurs with good to high yields and excellent stereoselectivities (up to 99% ee, >20?:?1 dr), providing an efficient and mild access to chiral benzothiazolopyrimidines bearing adjacent tertiary and quaternary stereogenic centers.
- Ni, Qijian,Wang, Xuyang,Xu, Fangfang,Chen, Xiaoyun,Song, Xiaoxiao
-
p. 3155 - 3158
(2020/03/23)
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- Asymmetric trifluoromethylthiolation of azlactones under chiral phase transfer catalysis
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The first enantioselective method for the installation of the SCF3 group at the C-4 position of azlactones is described in the present communication under quinidinium phase transfer catalysis. The higher performance of substrates containing electron-rich 2-aryl groups at the azlactone was rationalized using DFT calculations.
- Alemán, José,Bernardi, Luca,Borello, Fabio,Cano, Rafael,Capaccio, Vito,Díaz-Tendero, Sergio,De Riccardis, Francesco,Della Sala, Giorgio,Rodríguez, Ricardo I.,Sicignano, Marina
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p. 2914 - 2920
(2020/04/28)
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- Asymmetric Aza-Diels-Alder Reactions of in Situ Generated β,β-Disubstituted α,β-Unsaturated N-H Ketimines Catalyzed by Chiral Phosphoric Acids
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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
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p. 5633 - 5639
(2020/07/14)
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- Rational Design of 2-Substituted DMAP- N-oxides as Acyl Transfer Catalysts: Dynamic Kinetic Resolution of Azlactones
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A novel concept that conversion of chiral 2-substituted DMAP into its DMAP-N-oxide could significantly enhance the catalytic activity and still be used as an acyl transfer catalyst is presented. A new type of chiral 2-substituted DMAP-N-oxides, derived from l-prolinamides, has been rationally designed, facilely synthesized, and applied in the dynamic kinetic resolution of azlactones. Using simple MeOH as the nucleophile, various l-amino acid derivatives were produced in high yields (up to 98% yield) and enantioselectivities (up to 96% ee). Furthermore, α-deuterium labeled l-phenylalanine derivative was also obtained. Experiments and DFT calculations revealed that in 2-substituted DMAP-N-oxide, the oxygen atom acted as the nucleophilic site and the N-H bond functioned as the H-bond donor. High enantioselectivity of the reaction was governed by steric factors, and the addition of benzoic acid reduced the activation energy by participating in the construction of a H-bond bridge. The theoretical chemical study indicated that only when attack directions of the chiral catalyst were fully considered could the correct calculation results be obtained. This work paves the way for the utilization of the C2 position of the pyridine ring and the development of chiral 2-substituted DMAP-N-oxides as efficient acyl transfer catalysts.
- Deng, Yun,Guo, Hai-Ming,Huang, Bin,Li, Ning,Qu, Gui-Rong,Tian, Yin,Wu, Xiao-Xia,Xie, Ming-Sheng
-
supporting information
p. 19226 - 19238
(2020/11/13)
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- Palladium-catalyzed asymmetric decarboxylative allylation of azlactone enol carbonates: Fast access to enantioenriched α-allyl quaternary amino acids
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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
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p. 732 - 741
(2019/01/09)
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- Enantioselective synthesis of pyrano[2,3-: C] pyrrole via an organocatalytic [4 + 2] cyclization reaction of dioxopyrrolidines and azlactones
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An enantioselective [4 + 2] cyclization reaction of dioxopyrrolidines and azlactones has been successfully developed through a squaramide catalysis strategy. This protocol provides an efficient and mild access to obtain pyrano[2,3-c]pyrrole scaffolds containing contiguous quaternary and tertiary stereogenic centers in excellent yields (up to 99%) with high levels of diastereo- and enantioselectivities (up to 99% ee). Two possible pathways were proposed to explain the observed stereoselectivity.
- Wang, Yichen,Chen, Yuzhen,Li, Xiaoping,Mao, Yukang,Chen, Weiwen,Zhan, Ruoting,Huang, Huicai
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p. 3945 - 3950
(2019/04/30)
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- Asymmetric construction of dihydrobenzofuran-2,5-dione derivatives via desymmetrization of p-quinols with azlactones
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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
-
-
- STRUCTURE AND SYNTHESIS OF HIGHLY FLUORINATED AMINO ACID DERIVATIVES
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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; 0174
(2018/09/19)
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- Metal-Free Insertion Reactions of Diazo Carbonyls to Azlactones
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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.
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p. 11399 - 11406
(2018/09/12)
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- 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 ?
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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
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p. 644 - 655
(2018/01/27)
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- Bifunctional squaramide-catalyzed synthesis of chiral dihydrocoumarins via ortho-quinone methides generated from 2-(1-tosylalkyl)phenols
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A bifunctional squaramide-catalyzed reaction of azlactones with o-quinone methides in situ generated from 2-(1-tosylalkyl)-phenols has been successfully developed under basic conditions, providing an efficient and mild access to chiral dihydrocoumarins bearing adjacent tertiary and quaternary stereogenic centers in high yields with excellent diastereo- and enantioselectivities.
- Zhou, Ji,Wang, Mao-Lin,Gao, Xiang,Jiang, Guo-Fang,Zhou, Yong-Gui
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p. 3531 - 3534
(2017/03/30)
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- Polyfluoroarylation of oxazolones: Access to non-natural fluorinated amino acids
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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.
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p. 4771 - 4774
(2017/07/06)
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- Synthesis of Variously Functionalized Azabicycloalkane Scaffolds by Domino Metathesis Reactions
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7,5-Fused azabicycloalkane scaffolds, carrying a quaternary stereocenter at C3 position of the lactam ring, can act as effective reverse-turn mimics and have proven to be useful intermediates for the preparation of Arg-Gly-Asp (RGD)-based cyclopentapeptides (cRGD) with nanomolar activity as αvβ3/αvβ5 integrin antagonists. Here, we report the synthesis of new azabicycloalkane scaffolds endowed at the C6 position with a para-substituted phenethyl side chain, which could be exploited to obtain cRGD-based bioconjugates that may find promising applications in anticancer therapy. By performing a domino cross enyne metathesis/ring-closing metathesis (CEYM/RCM) in the presence of styrene derivatives, followed by catalytic hydrogenation of the diene system, we easily converted a dipeptide precursor into the desired C6-functionalized azabicycloalkane scaffolds. The presence of a suitably protected p-amino group on the styrene moiety could be exploited, after deprotection, either to directly conjugate a bioactive compound or to introduce a suitable spacer between the cRGD unit and the bioactive compound.
- Serra, Massimo,Peviani, Elena Giulia,Bernardi, Eric,Colombo, Lino
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p. 11091 - 11101
(2017/10/27)
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- One-Pot Vinylation of Azlactones: Fast Access to Enantioenriched α-Vinyl Quaternary Amino Acids
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We report a fast one-pot protocol for the direct vinylation of azlactones [oxazol-5-(4H)-ones] by using as a key step an aldol addition with 2-(phenylselenenyl)acetaldehyde followed by dehydroxyselenation. The acid hydrolysis of the oxazolone ring gave the desired fully deprotected α-vinyl quaternary α-amino acids in almost quantitative yields. An enantioselective variant of the method was also developed by using catalytic chiral bases. The use of Sharpless ligand (DHQD)2PHAL produced the final quaternary amino acids in good overall yields (62–78 %) and with ee values up to 86 %. Scaling up the optimized protocol to gram quantities did not affect the yields and ee values. We also demonstrated that the vinyl moiety installed onto the oxazolone ring can be exploited as a handle for the attachment of aryl groups through a Heck coupling reaction.
- Serra, Massimo,Bernardi, Eric,Marrubini, Giorgio,Colombo, Lino
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p. 2964 - 2970
(2017/06/06)
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- Alkynylation of heterocyclic compounds using hypervalent iodine reagent
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The alkynylation of various nitrogen- and/or sulphur-containing heterocyclic compounds using hypervalent iodine TMS-EBX by utilization of tertiary amines under mild conditions is described. The developed metal-free methodology furnishes the corresponding alkynylated heterocycles bearing quaternary carbon in high yields.
- Kamlar,Císa?ová,Vesely
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supporting information
p. 2884 - 2889
(2015/04/27)
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- Enantioselective synthesis of dihydrocoumarin derivatives by chiral scandium(iii)-complex catalyzed inverse-electron-demand hetero-Diels-Alder reaction
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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
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supporting information
p. 3835 - 3837
(2015/03/31)
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- Peptide-catalyzed conversion of racemic oxazol-5(4 H)-ones into enantiomerically enriched α-amino acid derivatives
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We report the development and optimization of a tetrapeptide that catalyzes the methanolytic dynamic kinetic resolution of oxazol-5(4H)-ones (azlactones) with high levels of enantioinduction. Oxazolones possessing benzylic-type substituents were found to perform better than others, providing methyl ester products in 88:12 to 98:2 er. The mechanism of this peptide-catalyzed process was investigated through truncation studies and competition experiments. High-field NOESY analysis was performed to elucidate the solution-phase structure of the peptide, and we present a plausible model for catalysis.
- Metrano, Anthony J.,Miller, Scott J.
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p. 1542 - 1554
(2014/03/21)
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- Bronsted acid accelerated Pd-catalyzed direct asymmetric allylic alkylation of azlactones with simple allylic alcohols: A practical access to quaternary allylic amino acid derivatives
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A Bronsted acid accelerated Pd-catalyzed asymmetric allylic alkylation of azlactones with simple allylic alcohols under mild reaction conditions has been realized, which provides a direct and readily scalable approach for the synthesis of all-carbon quaternary allylic amino acid derivatives in excellent yields and good enantioselectivities. (Chemical Equation Presented).
- Zhou, Hui,Yang, Huameng,Liu, Muwen,Xia, Chungu,Jiang, Gaoxi
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p. 5350 - 5353
(2015/01/09)
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- Organocatalyzed asymmetric 1,4-addition of azlactones to α,β-unsaturated trichloromethyl ketones: Synthesis of α,α-disubstituted α-amino acid derivatives
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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
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p. 7104 - 7108
(2015/01/16)
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- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
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Catalytic and asymmetric Michael reactions constitute very powerful tools for the construction of new C-C bonds in synthesis, but most of the reports claiming high selectivity are limited to some specific combinations of nucleophile/electrophile compound types, and only few successful methods deal with the generation of all-carbon quaternary stereocenters. A contribution to solve this gap is presented here based on chiral bifunctional Bronsted base (BB) catalysis and the use of α′-oxy enones as enabling Michael acceptors with ambivalent H-bond acceptor/donor character, a yet unreported design element for bidentate enoate equivalents. It is found that the Michael addition of a range of enolizable carbonyl compounds that have previously demonstrated challenging (i.e., α-substituted 2-oxindoles, cyanoesters, oxazolones, thiazolones, and azlactones) to α′-oxy enones can afford the corresponding tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α′-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical manipulations of the ketol moiety in adducts can produce the corresponding carboxy, aldehyde, and ketone compounds under very mild conditions, giving access to a variety of enantioenriched densely functionalized building blocks containing a fully substituted carbon stereocenter. A computational investigation to rationalize the mode of substrate activation and the reaction stereochemistry is also provided, and the proposed models are compared with related systems in the literature.
- Badiola, Eider,Fiser, Bla,Gmez-Bengoa, Enrique,Mielgo, Antonia,Olaizola, Iurre,Urruzuno, Iaki,Garca, Jess M.,Odriozola, Jos M.,Razkin, Jess,Oiarbide, Mikel,Palomo, Claudio
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p. 17869 - 17881
(2015/02/19)
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- Alkynyliodonium salt mediated alkynylation of azlactones: Fast access to Cα-tetrasubstituted α-amino acid derivatives
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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.
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supporting information
p. 1326 - 1329
(2014/04/03)
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- Organocatalytic oxyamination of azlactones: Kinetic resolution of oxaziridines and asymmetric synthesis of oxazolin-4-ones
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The first example of oxyamination of azlactones with oxaziridines was realized using a chiral bisguanidinium salt. Efficient catalytic asymmetric oxyamination and kinetic resolution of oxaziridines occurred simultaneously. Various chiral oxazolin-4-one derivatives with potential biological activity were obtained (up to 92% ee). Meanwhile, a series of optically pure oxaziridines were recovered with up to 99% ee and successfully used in the asymmetric oxyamination of 3-methyl-1H-indole and styrene. The triple stereodifferentiation process was also studied via control experiments.
- Dong, Shunxi,Liu, Xiaohua,Zhu, Yin,He, Peng,Lin, Lili,Feng, Xiaoming
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supporting information
p. 10026 - 10029
(2013/07/26)
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- Enantioselective quaternization of 4-substituted oxazol-5-(4H)-ones using recoverable Cinchona-derived dimeric ammonium salts as phase-transfer organocatalysts
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Dimeric anthracenyldimethyl-derived Cinchona ammonium salts are used as chiral organocatalysts (5 mol %) for the enantioselective 4-alkylation of 4-substituted azlactones. The corresponding adducts bearing a new quaternary center were obtained with up to
- Tari, Silvia,Avila, Angel,Chinchilla, Rafael,Najera, Carmen
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experimental part
p. 176 - 180
(2012/05/20)
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- Bispalladacycle-catalyzed Michael addition of in situ formed azlactones to enones
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The development and further evolution of the first catalytic asymmetric conjugate additions of azlactones as activated amino acid derivatives to enones is described. Whereas the first-generation approach started from isolated azlactones, in the second-generation approach the azlactones could be generated in situ starting from racemic N-benzoylated amino acids. The third evolution stage could make use of racemic unprotected α-amino acids to directly form highly enantioenriched and diastereomerically pure masked quaternary amino acid products bearing an additional tertiary stereocenter. The step-economic transformations were accomplished by cooperative activation by using a robust planar chiral bis-Pd catalyst, a Br?nsted acid (HOAc or BzOH; Ac=acetyl, Bz=benzoyl), and a Br?nsted base (NaOAc). In particular the second- and third-generation approaches provide a rapid and divergent access to biologically interesting unnatural quaternary amino acid derivatives from inexpensive bulk chemicals. In that way highly enantioenriched acyclic α-amino acids, α-alkyl proline, and α-alkyl pyroglutamic acid derivatives could be prepared in diastereomerically pure form. In addition, a unique way is presented to prepare diastereomerically pure bicyclic dipeptides in just two steps from unprotected tertiary α-amino acids. Flourishing step economy: The evolution of the catalytic asymmetric addition of azlactones to enones is described. The first-generation approach started from isolated azlactones. In the second-generation approach azlactones could be generated in situ from racemic N-benzoylated amino acids. The third evolution stage could directly use racemic unprotected α-amino acids to form a large number of highly enantioenriched quaternary amino acids derivatives (see figure). Copyright
- Weber, Manuel,Jautze, Sascha,Frey, Wolfgang,Peters, René
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supporting information
p. 14792 - 14804
(2013/01/15)
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- One-pot preparation of oxazol-5(4H)-ones from amino acids in aqueous solvents
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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
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p. 907 - 912
(2012/08/08)
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- Polyclonal antibodies: A cheap and efficient tool for screening of enantioselective catalysts
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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
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p. 4411 - 4413
(2012/05/20)
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- One-pot synthesis of 2,4,5-trisubstituted oxazoles from N-acyl amino acids by a combination of cyclodehydration with N,N′-diisopropylcarbodiimide and Wittig olefination
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By a combination of cyclodehydration of N-acyl amino acids with N,N′-diisopropylcarbodiimide (DIC) and non-classical Wittig olefination of the resultant 5(4H)-oxazolones with Ph3PCHCN and Ph 3PCHCOOEt, 5-oxazoleacetonitriles and 5-oxazoleacetates were synthesized in one-pot in 41-85% and 57-70% yields, respectively.
- Huang, Wenhua,Dong, Guangping,Mijiti, Zumureti
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experimental part
p. 977 - 981
(2012/02/13)
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- Asymmetric synthesis of 3, 4-diaminochroman-2-ones promoted by guanidine and bisguanidium salt
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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
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supporting information; experimental part
p. 5060 - 5063
(2011/12/05)
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- Synthesis of 1,2,4-Triazolines and triazoles utilizing oxazolones
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We describe herein a convenient method for the synthesis of 1,2,4-triazolines using oxazolones and azodicarboxylates. Subsequent treatment of these 1,2,4-triazolines with NaOH provides efficient access to the corresponding triazoles.
- Saleem, Rahman Shah Zaib,Tepe, Jetze J.
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supporting information; experimental part
p. 4330 - 4332
(2010/09/03)
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- Dynamic kinetic resolution of N-benzoyl-DL-amino acids via peptide bond forming reactions
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Dynamic kinetic resolution (DKR) was demonstrated in the carbodiimide-mediated couplings of N-benzoyl-DL-amino acids with L-amino acid esters: the yields of the D-L-peptides significantly exceeded 50% in some cases. N-benzoyl-DL-t-leucine afforded the D-L-peptide almost exclusively (up to 96% yield) in the reaction with methyl L-prolinate, which is the most efficient DKR obtained in the field of amino acids and derivatives.
- Miyazawa, Toshifumi,Hamada, Takashi
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body text
p. 419 - 422
(2011/12/04)
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- A new method proposed for the determination of absolute configurations of α-amino acids
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Enantiopure α-amino acids were converted to 4-substituted 2-aryl- and 2-alkyl-5(4H)-oxazolones under partial racemization. These nonracemic mixtures were dissolved in CDCl3, an equimolar amount of the chiral dirhodium complex Rh2(II)[(R)-(+)-MTPA]4 (MTPA-H = Mosher's acid) was added, and the 1H NMR spectra of the resulting samples were recorded [dirhodium method). The relative intensities of 1H signals dispersed by the formation of diastereomeric adducts allow to determine the absolute configuration (AC) of the starting a-amino acids. Binding atoms in the adducts were identified by comparing the 1H and 13C chemical shifts of the oxazolones in the absence and presence of Rh2(II)[(R)-(+)- MTPA]4. Thereby, information about the scope and limits of this method can be extracted. A protocol how to use this method is presented. Copyright
- Gomez, Edison Diaz,Duddeck, Helmut
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experimental part
p. 222 - 227
(2010/02/28)
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- Regioselective synthesis of tetrasubstituted pyrroles by 1,3-dipolar cycloaddition and spontaneous decarboxylation
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We developed a novel regioselective synthesis of tetrasubstituted pyrroles via the classic 1,3-dipolar cycloaddition of α,β-unsaturated benzofuran-3(2H)-one and azlactones (1) followed by spontaneous decarboxylation. The complete regiochemical control of tetrasubstituted pyrroles was confirmed by the orthogonal synthesis of complementary regioisomers (7a and 7b) simply by using different azlactones (1a and 1b, respectively).
- Kim, Yongju,Kim, Jonghoon,Park, Seung Bum
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supporting information; experimental part
p. 17 - 20
(2009/08/07)
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- Structural-activity relationship study of highly-functionalized imidazolines as potent inhibitors of nuclear transcription factor-κB mediated IL-6 production
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We herein describe the synthesis and anti-inflammatory properties of a small library of imidazoline-based NF-κB inhibitors. The structure-activity relationship of various substituents on an imidazoline core structure was evaluated for the ability to inhibit NF-κB mediated IL-6 production. Optimization of the scaffolds was pursued by correlating luciferase-based NF-κB reporter assays with inhibition of IL-6 production in IL-1β stimulated human blood. Several derivatives were found to inhibit NF-κB mediated IL-6 production in the nanomolar range in IL-1β stimulated human blood.
- Kahlon, Daljinder K.,Lansdell, Theresa A.,Fisk, Jason S.,Tepe, Jetze J.
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body text
p. 3093 - 3103
(2009/10/02)
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- Au(I)-catalyzed enantioselective 1,3-dipolar cycloadditions of muenchnones with electron-deficient alkenes
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The first catalytic enantioselective 1,3-dipolar cycloaddition of muenchnone dipoles with electron-deficent alkenes is described. The reaction is catalyzed by chiral bis(phosphine)gold(I) benzoate complexes and provides Δ1-pyrrolines with excellent regio-, diastereo-, and enantioselectivity. The reaction is proposed to proceed througha 1,3-dipole generated by deprotonation of a gold(I)-activated azlactone. Copyright
- Melhado, Asa D.,Luparia, Marco,Toste, F. Dean
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p. 12638 - 12639
(2008/03/14)
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- Structural optimization of thiourea-based bifunctional organocatalysts for the highly enantioselective dynamic kinetic resolution of azlactones
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This article describes the synthesis of a library of structurally diverse bifunctional organocatalysts bearing both a quasi-Lewis acidic (thio)urea moiety and a Bronsted basic tertiary amine group. Sequential modification of the modular catalyst structure and subsequent screening of the compounds in the alcoholytic dynamic kinetic resolution (DKR) of azlactones revealed valuable structure-activity relationships. In particular, a "hit-structure" was identified which provides e.g. N-benzoyl-tert-leucine allyl ester in an excellent enantiomeric excess of 95%. The Royal Society of Chemistry 2006.
- Berkessel, Albrecht,Mukherjee, Santanu,Mueller, Thomas N.,Cleemann, Felix,Roland, Katrin,Brandenburg, Marc,Neudoerfl, Joerg-M.,Lex, Johann
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p. 4319 - 4330
(2008/09/18)
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- Highly efficient dynamic kinetic resolution of azlactones by urea-based bifunctional organocatalysts
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Novel tasks for a venerable molecule: Bifunctional organocatalysts of the type shown, with a quasi Lewis acidic urea or thiourea unit and a Bronsted basic amine functionality, effect the dynamic kinetic resolution of azlactones with high enantioselectivit
- Berkessel, Albrecht,Cleemann, Felix,Mukherjee, Santanu,Mueller, Thomas N.,Lex, Johann
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p. 807 - 811
(2007/10/03)
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- Diastereochemical diversity of imidazoline scaffolds via substrate controlled TMSCI mediated cycloaddition of azlactones
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(Chemical Equation Presented) We report herein a trimethylsilyl chloride mediated substrate controlled 1,3-dipolar cycloaddition for the diastereoselective synthesis of either syn- or anti-imidazolines. This method provides scaffolds with four points of diversity and control over two stereocenters.
- Sharma, Vasudha,Tepe, Jetze J.
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p. 5091 - 5094
(2007/10/03)
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- THIAZOLIDINE DERIVATIVES
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An object of the present invention is to provide novel thiazolidine derivatives which are useful as drugs. The thiazolidine derivatives according to the present invention are compounds represented by the following general formula [I] and salts thereof, wherein R 1is alkyl, hydroxy, alkoxy, alkoxyalkyl, phenyl, phenylalkyl, phenylalkoxy, phenoxy, phenoxyalkyl, amino, alkylamino or a nonaromatic heterocycle; R 2is H or alkyl; R 3is H, alkyl or phenyl; R 4is H or alkyl; R 5is alkyl, halogenoalkyl, hydroxy, alkoxy, phenyl, phenylalkoxy, phenoxy, carboxyl, alkoxycarbonyl, phenylalkoxycarbonyl or an aromatic heterocycle; A 1is alkylene; and A 2is alkylene.
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- NOVEL THIAZINE OR PYRAZINE DERIVATIVES
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An object of the present invention is to synthesize novel compounds having 3-oxo-3, 4-dihydro-2H-1, 4-thiazine or 2-oxo-1, 2, 3, 4-tetrahydropyrazine as a main skeleton. The present invention relates to compounds represented by the following general formula [I] and salts thereof. In the formula, X is S or R6-(A2)n-N, R1 and R2 are H, alkyl, cycloalkyl or aryl, R3 and R4 are H, alkyl, cycloalkyl, aryl or aromatic heterocycles, R5 is H, alkyl, cycloalkyl, aryl or -A3-A4-R7, R6 is H, alkyl, cycloalkyl, OH, alkoxy, aryl, aryloxy or an aromatic heterocycle, R7 is H, alkyl, OH, alkoxy, aryl, aryloxy, amino, alkylamino, arylamino, an aromatic heterocycle or a nonaromatic heterocycle, A1 is alkylene, A2 is carbonyl or sulfonyl, A3 is alkylene, and A4 is carbonyl or oxalyl.
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- Optical resolution by preferential crystallization of (RS)-2-benzoylamino-2-benzyl-3-hydroxypropanoic acid and its use in synthesizing optically active 2-amino-2-methyl-3-phenylpropanoic acid.
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To synthesize optically active 2-amino-2-methyl-3-phenylpropanoic acid (1), (RS)-2-benzoylamino-2-benzyl-3-hydroxypropanoic acid [(RS)-2] was first optically resolved using cinchonidine as a resolving agent to yield optically pure (S)- and (R)-2 in yields of about 70%, based on half of the starting amount of (RS)-2. Next, the racemic structure of (RS)-2 was examined based on melting point, solubility, IR spectrum, and binary and ternary phase diagrams, with the aim of optical resolution by preferential crystallization of (RS)-2. Results indicated that the (RS)-2 exists as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization yielded (S)- and (R)-2 with optical purities of about 90%, which were fully purified by recrystallization. After O-tosylation of (S)- and (R)-2, reduction by zinc powder and sodium iodide gave (R)- and (S)-1, respectively.
- Shiraiwa, Tadashi,Suzuki, Masahiro,Sakai, Yoshio,Nagasawa, Hisashi,Takatani, Kazuhiro,Noshi, Daisuke,Yamanashi, Kenji
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p. 1362 - 1366
(2007/10/03)
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- Enantiomerically enriched alpha , alpha -distributed amino acids and method
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Compositions and methods for the preparation of enantiomerically enriched alpha , alpha -disubstituted amino acid precursors are presented. Briefly, allylic electrophiles are alkylated with oxazolones in the presence of a base and catalytic quantities of
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- HETEROCYCLIC AMIDE COMPOUNDS AND PHARMACEUTICAL USE OF THE SAME
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Heterocyclic amide compounds of the formula (I) STR1 wherein each symbol is as defined in the specification, pharmacologically acceptable salts thereof, pharmaceutical compositions thereof and pharmaceutical use thereof. The heterocyclic amide compounds and pharmacologically acceptable salts thereof of the present invention have superior inhibitory activity against chymase groups in mammals inclusive of human, and can be administered orally or parenterally. Therefore, they are useful as chymase inhibitors and can be effective for the prophylaxis and treatment of various diseases caused by chymase, such as those caused by angiotensin II.
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- Ring opening with kinetic resolution of azlactones by Ti-TADDOLates
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The kinetic resolution of azlactones by the Lewis, acid-mediated transfer of an isopropoxide ligand from the chiral ligand sphere of Ti- TADDOLate is described. The reactions proceed with in-situ racemization of the starting material to afford highly enantiomerically enriched N-benzoyl- amino acid isopropylesters (er > 95:5 after recrystallization). The absolute configuration of the major enantiomer of N-benzoyl-phenylalanine isopropyl ester and its analogs with other aromatic substituents was shown to be (S)- (+) when the (R,R)-Ti-TADDOLate was employed. Only benzyl-substituted azlactones can be opened enantioselectively by the method described here.
- Gottwald, Konstanze,Seebach, Dieter
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p. 723 - 738
(2007/10/03)
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- An efficient strategy to orthogonally protected (R)- and (S)-α-methyl(alkyl)serine-containing peptides via a novel azlactone/oxazoline interconversion reaction
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A novel strategy for the synthesis of (R)- and (S)-α-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-α-methylserine and can be directly incorporated into peptides without further protective group manipulations. Like other α,α-dialkylated glycines, optically pure α-alkylserines can be used to stabilize β-turn and α-helical conformations in short peptides.
- Obrecht, Daniel,Altorfer, Michael,Lehmann, Christian,Sch?nholzer, Peter,Müller, Klaus
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p. 4080 - 4086
(2007/10/03)
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- An Unexpected Ring Enlargemant of 3-(Dimethylamino)-2,2-dimethyl-2H-azirine to 4,5-Dihydropyridin-2(3H)-one Derivatives
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The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1a) and 4,4-disubstituted 2-(trifluoromethyl)-1,3-oxazol-5(4H)-ones 7 in MeCN at 70 deg afforded 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 10 (Scheme 4), whereas no reaction could be observed between 1a and 2-allyl-4-phenyl-2-(trifluoromethyl)-1,3-oxazol-5(2H)-one (8a) or 4,4-dibenzyl-2-phenyl-1,3-oxazol-5(4H)-one (9).The formation of 10 is rationalized by a mechanism via nucleophilic attack of 1a onto 7.The failure of a reaction with 9 shows that only activated 1,3-oxazol-5(4H)-ones bearing electron-withdrawing substituents do react as electrophiles with 1a.The amino-azirine 1a and 2,4-disubstituted 1,3-oxazol-5(4H)-ones 2b-e in refluxing MeCN undergo a novel ring enlargement to 4,5-dihydropyridin-2(3H)-ones 11 (Scheme 5).Several side products were observed in these reactions.Two different reaction mechanisms for the formation of 11 are proposed: either 1a undergoes a nucleophilic addition onto the open-chain ketene tautomer of 2 (Scheme 6), or 2 reacts as CH-acidic compound (Scheme 7).
- Hugener, Martin,Heimgartner, Heinz
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p. 1863 - 1878
(2007/10/02)
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- A reinvestigation of the α-alkylation of 4-monosubstituted 2-phenyloxazol-5(4H)-ones ('azlactones'): A general entry into highly functionalized α,α-disubstituted α-amino acids
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Novel, more reliable and general reaction conditions for the α-alkylation of 4-monosubstituted 2-phenyloxazol-5(4H)-ones (= 4-monosubstituted 2-phenyl-azlactones) rac-2 to 4,4-disubstituted 2-phenyloxazol-5(4H)-ones rac-1 were found. Thus, a whole range of highly functionalized rac-1 were prepared in medium-to-good overall yields (40-90%). Azlactones rac-1 are ideal precursors for the synthesis of optically pure α,α-disubstituted (R)- and (S)-α-amino acids.
- Obrecht,Bohdal,Ruffieux,Muller
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p. 1423 - 1429
(2007/10/02)
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- STUDIES ON THE KINETICS OF RACEMIZATION OF 2,4-DISUBSTITUTED-5(4H)-OXAZOLONES
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The kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones obtained from N-acetyl, N-benzoyl, and N-benzyloxycarbonylglycyl-L-leucine, -valine, and -phenylalanine have been studied in several solvents alone and in the presence of tertiary amines.T
- Slebioda, Marek,St-Amand, Marc A.,Chen, Francis M. F.,Benoiton, N. Leo
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p. 2540 - 2544
(2007/10/02)
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- SYNTHESIS OF FLUORINATED α-AMINO KETONES PART I: α-BENZAMIDOALKYL MONO- DI- AND TRIFLUOROMETHYL KETONES
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2-Phenyl-5(4H)-oxazolones, obtained from α-amino acids, are reacted with di- and trifluoro acetic anhydride by a modified Dakin-West procedure to yield in a one-pot reaction α-benzamidoalkyl-di- and trifluoromethyl ketones in good yields.The monofluoromethyl analogues were also prepared from α-amino acids, however the use of the highly toxic fluoroacetic anhydride was avoided.The key step is the halogen exchange reaction on the corresponding bromomethyl ketone.
- Kolb, Michael,Barth, Jacqueline,Neises, Bernhard
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p. 1579 - 1582
(2007/10/02)
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