- Base-catalysed 18F-labelling of trifluoromethyl ketones. Application to the synthesis of 18F-labelled neutrophil elastase inhibitors
-
A new method for the fluorine-18 labelling of trifluoromethyl ketones has been developed. This method is based on the conversion of a-COCF3 functional group to a difluoro enol silyl ether followed by halogenation and fluorine-18 labelling. The utility of this new method was demonstrated by the synthesis of fluorine-18 labelled neutrophil elastase inhibitors, which are potentially useful for detection of inflammatory disorders.
- Meyer, Denise N.,Cortés González, Miguel A.,Jiang, Xingguo,Johansson-Holm, Linus,Pourghasemi Lati, Monireh,Elgland, Mathias,Nordeman, Patrik,Antoni, Gunnar,Szabó, Kálmán J.
-
p. 8476 - 8479
(2021/09/02)
-
- Transformation of Racemic Azlactones into Enantioenriched Dihydropyrroles and Lactones Enabled by Hydrogen-Bond Organocatalysis
-
Azlactones, a potent building block for the synthesis of complex molecules, have been explored in an organocatalytic Mannich reaction with protected imines. In this study, azlactones containing a propargyl substituent were employed for the first time in organocatalysis so far. The catalytically active species responsible for high enantioselectivity with substrate containing such a small linear substituent is assembled in situ from a bifunctional thiourea, prone to dimerization, and an organic acid, as evidenced by DOSY NMR. The resulting α,β-diamino acid derivatives were subjected to further derivatization: as an example, gold-catalyzed intramolecular hydroamination of alkynes gave chiral spirocyclic dihydropyrrole. Alternatively, related squaramide catalyst enabled a Mannich reaction of azlactones with N-aryl or alkyl glyoxylate imines. Reduction of these adducts gave access to 2,3-diaminobutyrolactones or 2,3-diamino-1,4-diol with a tertiary and a quaternary stereocenter.
- ?abka, Matej,Kocian, Adrián,Bilka, Stanislav,Andrej?ák, Samuel,?ebesta, Radovan
-
p. 6077 - 6087
(2019/09/12)
-
- 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)
-
- One-Pot Vinylation of Azlactones: Fast Access to Enantioenriched α-Vinyl Quaternary Amino Acids
-
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
-
p. 2964 - 2970
(2017/06/06)
-
- Peptide-catalyzed conversion of racemic oxazol-5(4 H)-ones into enantiomerically enriched α-amino acid derivatives
-
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.
-
p. 1542 - 1554
(2014/03/21)
-
- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
-
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
-
p. 17869 - 17881
(2015/02/19)
-
- BENZAMIDE TRPA1 ANTAGONISTS
-
Compounds of formula I, pharmaceutically acceptable salts thereof, diastereomers, enantiomers, or mixtures thereof: wherein R, X, Y, Z, n and A are as defined in the specification, as well as pharmaceutical compositions including the compounds are prepared. They are useful in therapy, in particular in the management of pain.
- -
-
Page/Page column 44
(2014/12/12)
-
- 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)
-
- Self-association free bifunctional thiourea organocatalysts: Synthesis of chiral α-amino acids via dynamic kinetic resolution of racemic azlactones
-
Concentration-independent high enantioselectivity in the dynamic kinetic resolution (DKR) of racemic azlactones affording chiral α-aminoesters has been achieved using self-association free thiourea-based dimeric cinchona alkaloid organocatalysts. Detailed
- Oh, Joong-Suk,Lee, Ji-Woong,Ryu, Tae Hee,Lee, Jae Heon,Song, Choong Eui
-
experimental part
p. 1052 - 1055
(2012/04/10)
-
- N-1-Alkyl-2-oxo-2-aryl amides as novel antagonists of the TRPA1 receptor
-
A series of potent antagonists of the ion channel transient receptor potential A1 (TRPA1) was developed by modifying lead structure 16 that was discovered by high-throughput screening. Based on lead compound 16, a SAR was established, showing a narrow region at the nitro-aromatic R1 moiety and at the warhead, while the R2 side had a much wider scope including ureas and carbamates. Compound 16 inhibits Ca2+-activated TRPA1 currents reversibly in whole cell patch clamp experiments, indicating that under in vivo conditions, it does not react covalently, despite its potentially electrophilic ketone.
- Vallin, Karl S.A.,Sterky, Karin J.,Nyman, Eva,Bernstroem, Jenny,From, Rebecka,Linde, Christian,Minidis, Alexander B.E.,Nolting, Andreas,Naerhi, Katja,Santangelo, Ellen M.,Sehgelmeble, Fernando W.,Sohn, Daniel,Strindlund, Jennie,Weigelt, Dirk
-
supporting information; experimental part
p. 5485 - 5492
(2012/09/22)
-
- 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)
-
- 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
-
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
-
experimental part
p. 977 - 981
(2012/02/13)
-
- 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)
-
- Synthesis of 1,2,4-Triazolines and triazoles utilizing oxazolones
-
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.
-
supporting information; experimental part
p. 4330 - 4332
(2010/09/03)
-
- Dynamic kinetic resolution of N-benzoyl-DL-amino acids via peptide bond forming reactions
-
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
-
body text
p. 419 - 422
(2011/12/04)
-
- A new method proposed for the determination of absolute configurations of α-amino acids
-
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
-
experimental part
p. 222 - 227
(2010/02/28)
-
- Synthesis and use of achiral oxazolidine-2-thiones in selective preparation of trans 2,5-disubstituted tetrahydrofurans
-
The use of achiral N-acetyloxazolidine-2-thiones in the C-glycosylation of lactol acetates has allowed us to prepare with high diastereoselectivity the expected trans 2,5-disubstituted tetrahydrofurans. A study based on the role of the steric hindrance of the N-acetyloxazolidine-2-thiones is reported. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Jalce, Gael,Franck, Xavier,Figadere, Bruno
-
body text
p. 378 - 386
(2009/09/25)
-
- Structural-activity relationship study of highly-functionalized imidazolines as potent inhibitors of nuclear transcription factor-κB mediated IL-6 production
-
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.
-
body text
p. 3093 - 3103
(2009/10/02)
-
- Highly efficient dynamic kinetic resolution of azlactones by urea-based bifunctional organocatalysts
-
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
-
p. 807 - 811
(2007/10/03)
-
- Diastereochemical diversity of imidazoline scaffolds via substrate controlled TMSCI mediated cycloaddition of azlactones
-
(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.
-
p. 5091 - 5094
(2007/10/03)
-
- Enantiomerically enriched alpha , alpha -distributed amino acids and method
-
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
- -
-
-
- Aminoketone, oxazole and thiazole synthesis. Part XIII. 1 new 2-aryl-6-phenyloxazoles with 4-methyl or 4-isopropyl groups
-
Benzoylation of (±)-α-alanine and (±)-valine followed by cyclization afforded the corresponding azlactones, which reacted with benzene, toluene, o- and m-xylene yielding substituted N-benzoyl-phenacylamines. Their cyclization in the presence of phosphorus oxychloride led to the title compounds whose electronic and NMR spectra (1H and 13C) are presented.
- Schiketanz, Iosif,Istrati, Daniela,Drǎghici, Constantin,Balaban, Alexandru T.
-
p. 137 - 142
(2007/10/03)
-
- An efficient strategy to orthogonally protected (R)- and (S)-α-methyl(alkyl)serine-containing peptides via a novel azlactone/oxazoline interconversion reaction
-
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
-
p. 4080 - 4086
(2007/10/03)
-
- An Unexpected Ring Enlargemant of 3-(Dimethylamino)-2,2-dimethyl-2H-azirine to 4,5-Dihydropyridin-2(3H)-one Derivatives
-
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
-
p. 1863 - 1878
(2007/10/02)
-
- 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
-
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
-
p. 1423 - 1429
(2007/10/02)
-
- Synthesis and anti-HIV-1 activity of a series of imidazo[1,5- b]pyridazines
-
A series of substituted imidazo[1,5-b]pyridazines have been prepared and tested for inhibitory activity against the reverse transcriptase of HIV-1 (RT) and their ability to inhibit the growth of infected MT-4 cells. Crystal data are reported on two compounds, 15c and 33. From the structure-activity relationships developed within this and other series, it is proposed that key features of the interaction with RT include hydrogen-bond acceptor and aromatic π-orbital bonding with the imidazopyridazine nucleus and a benzoyl function separated from the heterocycle by a suitable spacer group. Exceptional activity against the reverse transcriptase of HIV-1 (IC50 = 0.65 nM) was obtained with a 2-imidazolyl-substituted derivative, 7-[2-(1H- imidazol-1-yl)-5-methylimidazo[1,5-b]pyridazin-7-yl]-1-phenyl-1-heptanone (33) which is attributed to additional binding of the imidazole sp2 nitrogen atom. A number of the compounds in this series also inhibit the replication of HIV-1 in vitro in MT-4 and C8166 cells at levels observed with the nucleoside AZT.
- Livermore,Bethell,Cammack,Hancock,Hann,Green,Lamont,Noble,Orr,Payne,Ramsay,Shingler,Smith,Storer,Williamson,Willson
-
p. 3784 - 3794
(2007/10/02)
-
- ASYMMETRIC SYNTHESIS OF AMINO ACIDS VIA THE CATALYTIC REDUCTION OF SUBSTITUTED ACYLAMINOACRYLIC ACID AZLACTONE DERIVATIVES. 25. REDUCTIVE AMINOLYSIS OF 2-PHENYL- AND 2-METHYL-Δ2-OXAZOLIN-5-ONES UPON TREATMENT WITH A CHIRAL PdCl2-R-PHENYLGLYCINE
-
We have studied the reaction of Δ2-oxazolin-5-ones with R-phenylglycine methyl ester in the presence of PdCl2; the reaction gives phenylalanine or valine dipeptide derivatives with the RS-configuration.The presence of triethylamine during the r
- Chel'tsova, G. V.,Karpeiskaya, E. I.,Klabunovskii, E. I.
-
p. 727 - 731
(2007/10/02)
-
- STUDIES ON THE KINETICS OF RACEMIZATION OF 2,4-DISUBSTITUTED-5(4H)-OXAZOLONES
-
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
-
p. 2540 - 2544
(2007/10/02)
-
- SYNTHESIS OF FLUORINATED α-AMINO KETONES PART I: α-BENZAMIDOALKYL MONO- DI- AND TRIFLUOROMETHYL KETONES
-
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
-
p. 1579 - 1582
(2007/10/02)
-
- 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)
-
- Studies on the Diastereoisomeric and Conformational Aspects of Benzoyl Dipeptide Esters, as a Means of assessing Racemisation using Nuclear Magnetic Resonance Spectroscopy
-
Distinct methyl ester signals in the 1H n.m.r. spectra of diastereoisomeric forms of benzoyl dipeptide methyl esters provide a means of estimating the isomer composition of diastereoisomeric mixtures.Analysis of the mixture derived from peptide-coupling r
- Davies, John S.,Thomas, R. John
-
p. 1639 - 1646
(2007/10/02)
-
