cas 32644-15-8, (S)-(-)-2-BROMOPROPIONIC ACID

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Enantioselective Construction of Axially Chiral Azepine-Containing P,N-Ligands from l -Alanine
A family of axially chiral azepine-containing seven-membered cyclic P,N-ligands (named Indole-azepinap) have been prepared by using l-alanine as an original chirality source. The direct chromatographic separation of two diastereomeric phosphine oxides on silica gel enabled these ligands to be easy available, allowing further structural and electronic modifications. Preliminary application of these Indole-azepinaps has been demonstrated in a Pd-catalyzed asymmetric allylic alkylation with high yields and moderate enantioselectivities.
Zhang, Jinlong,Gao, Zeng,Qian, Jinlong,Yang, Huameng,He, Maosheng,Jiang, Gaoxi
supporting information
p. 7814 - 7818
(2021/10/20)

Atropselective Dibrominations of a 1,1′-Disubstituted 2,2′-Biindolyl with Diverging Point-to-Axial Asymmetric Inductions. Deriving 2,2′-Biindolyl-3,3′-diphosphane Ligands for Asymmetric Catalysis
On the 1H NMR timescale, 2,2′-biindolyls with (R)-configured (1-alkoxyprop)-2-yl, (1-hydroxyprop)-2-yl, or (1-siloxyprop)-2-yl substituents at C-1 and C-1′ are atropisomerically stable at 30 °C. A 2,2′-biindolyl (R,R)-17 a of that kind and achiral (!) brominating reagents gave the atropisomerically stable 3,3′-dibromobiindolyls (M)- and/or (P)-18 a at best atropselectively—because of point-to-axial asymmetric inductions—and atropdivergently, exhibiting up to 95 % (M)- and as much (P)-atropselectivity. This route to atropisomerically pure biaryls is novel and should extend to other substrates and/or different functionalizations. The dibromobiindolyls (M)- and (P)-18 a furnished the biindolyldiphosphanes (M)- and (P)-14 without atropisomerization. These syntheses did not require the resolution of a racemic mixture, which distinguishes them from virtually all biaryldiphosphane syntheses known to date. (M)- and (P)-14 acted as ligands in catalytic asymmetric allylations and hydrogenations. Remarkably, the β-ketoester rac-25 c was hydrogenated trans-selectively with 98 % ee; this included a dynamic kinetic resolution.
Baumann, Thomas,Brückner, Reinhard
supporting information
p. 4714 - 4719
(2019/03/26)

α-Aminoxy Oligopeptides: Synthesis, Secondary Structure, and Cytotoxicity of a New Class of Anticancer Foldamers
α-Aminoxy peptides are peptidomimetic foldamers with high proteolytic and conformational stability. To gain an improved synthetic access to α-aminoxy oligopeptides we used a straightforward combination of solution- and solid-phase-supported methods and obtained oligomers that showed a remarkable anticancer activity against a panel of cancer cell lines. We solved the first X-ray crystal structure of an α-aminoxy peptide with multiple turns around the helical axis. The crystal structure revealed a right-handed 28-helical conformation with precisely two residues per turn and a helical pitch of 5.8 ?. By 2D ROESY experiments, molecular dynamics simulations, and CD spectroscopy we were able to identify the 28-helix as the predominant conformation in organic solvents. In aqueous solution, the α-aminoxy peptides exist in the 28-helical conformation at acidic pH, but exhibit remarkable changes in the secondary structure with increasing pH. The most cytotoxic α-aminoxy peptides have an increased propensity to take up a 28-helical conformation in the presence of a model membrane. This indicates a correlation between the 28-helical conformation and the membranolytic activity observed in mode of action studies, thereby providing novel insights in the folding properties and the biological activity of α-aminoxy peptides.
Diedrich, Daniela,Moita, Ana J. Rodrigues,Rüther, Anja,Frieg, Benedikt,Reiss, Guido J.,Hoeppner, Astrid,Kurz, Thomas,Gohlke, Holger,Lüdeke, Steffen,Kassack, Matthias U.,Hansen, Finn K.
p. 17600 - 17611
(2016/11/28)

Synthesis of tertiary and quaternary amine derivatives from wood resin as chiral NMR solvating agents
Chiral tertiary and quaternary amine solvating agents for NMR spectroscopy were synthesized from the wood resin derivative (+)-dehydroabietylamine (2). The resolution of enantiomers of model compounds [Mosher's acid (3) and its n-Bu4N salt (4)] (guests) by (+)-dehydroabietyl-N,N-dimethylmethanamine (5) and its ten different ammonium salts (hosts) was studied. The best results with 3 were obtained using 5 while with 4 the best enantiomeric resolution was obtained using (+)-dehydroabietyl-N,N-dimethylmethanaminium bis(trifluoromethane-sulfonimide) (6). The compounds 5 and 6 showed a 1:1 complexation behaviour between the host and guest. The capability of 5 and 6 to recognize the enantiomers of various α-substituted carboxylic acids and their n-Bu4N salts in enantiomeric excess (ee) determinations was demonstrated. A modification of the RES-TOCSY NMR pulse sequence is described, allowing the enhancement of enantiomeric discrimination when the resolution of multiplets is insufficient.
Laaksonen, Tiina,Heikkinen, Sami,W?h?l?, Kristiina
supporting information
p. 20873 - 20886
(2015/12/23)

Enantioselective protonation of α-hetero carboxylic acid-derived ketene disilyl acetals under chiral ionic Bronsted acid catalysis
Highly enantioselective protonation of α-halo and alkoxy carboxylic acid-derived ketene disilyl acetals is achieved by using P-spiro chiral diaminodioxaphosphonium barfate as a Bronsted acid catalyst, where the enantiofacial discrimination by the catalyst mainly stems from the recognition of the electronic difference between two substituents on the ketene disilyl acetal.
Uraguchi, Daisuke,Kizu, Tomohito,Ohira, Yuki,Ooi, Takashi
supporting information
p. 13489 - 13491
(2015/01/09)

Synthesis of enantiomerically enriched-bromonitriles from amino acids
Two methods were investigated for the preparation of six chiral-bromonitriles with different optic purities. The nitrous deamination of amino acids gives-bromoacids, which react with chlorosulfonyl isocyanate followed by triethylamine to afford-bromonitriles with moderate enantiomeric excess. However, the dehydration of corresponding-bromoamids using thionyl chloride gives-bromonitriles with good enantiomeric excess up to 94%. The use of phosphoryl chloride instead of thionyl chloride results in more than 30% racemization as determined by high-performance liquid chromatograpic analysis.
Tka, Najeh,Kraem, Jamil,Hassine, Bechir Ben
p. 735 - 743
(2013/01/15)

Syntheses of hydrazino peptides and conjugates
(α-Benzyloxycarbonyl-aminoacyl)benzotriazolides (Cbz = benzyloxycarbonyl) underwent a coupling reaction with α-hydrazino acids under microwave irradiation to form hybrid hydrazino dipeptides (42-71 %). Chiral acylations of β-N-Cbz-α-hydrazino acylbenzotriazolides were successfully carried out with N-, S-, O-, and C-nucleophiles in yields of 49-88 %. Benzyloxycarbonyl-protected hybrid hydrazino dipeptides and benzyloxycarbonyl-protected hydrazino aminoacyl conjugates with N-, S-, O-, and C-nucleophiles were prepared by using benzotriazole methodology. Copyright
Panda, Siva S.,El-Nachef, Claudia,Bajaj, Kiran,Katritzky, Alan R.
p. 4156 - 4162
(2013/07/19)

Conformational preference in bis(porphyrin) tweezer complexes: A versatile chirality sensor for α-chiral carboxylic acids
Metallated porphyrin tweezers have demonstrated a remarkable ability to function as reporters of absolute stereochemistry for a number of different classes of organic molecules. Flexibility in binding, however, can result in an ensemble of different Exciton Coupled Circular Dichroism (ECCD) active conformations that could lead to variable results. Linker flexibility was found to be a key determinant of binding conformation. Experimental results indicate that a balance between linker flexibility and rigidity could yield an optimum porphyrin tweezer that stabilizes a common conformation for all bound chiral guests. This leads to a more simplified approach to absolute stereochemical determination of asymmetry for small organic molecules. This was demonstrated by the use of a C3-linked zincated porphyrin tweezer that yields a common conformational preference for a variety of α-chiral carboxylic acids derivatized with a diamine carrier. Copyright
Tanasova, Marina,Borhan, Babak
supporting information; experimental part
p. 3261 - 3269
(2012/07/01)

Enantio-and diastereoselective oxidation of N-alkylimines using chiral-bromonitriles and hydrogen peroxide system
Chiral-bromonitriles were prepared with good chemical and optical yields starting from natural-amino acids by dehydrating the corresponding α-bromoamides with thionyl chloride. The combined system-bromonitriles/ hydrogen peroxide was examined for the enantio-and diastereoselective oxidation of N-alkylimines in basic media at room temperature. The oxidation of N-tertiobutylarylimines leads to optically active oxaziridines with moderate enantiomeric excess. However, the oxidation of (S)-1-phenylethylarylimines affords the corresponding oxaziridines with good diasteromeric excess up to 97/3 as proved by gaseous-phase chromatography.
Tka, Najeh,Kraem, Jamil,Hassine, Bechir Ben
scheme or table
p. 2994 - 3003
(2012/08/07)

MACROCYCLIC INHIBITORS OF HEPATITIS C PROTEASE
The invention provides macrocyclic compounds inhibitory to the Hepatitis C viral protease, compositions and combinations including the compounds, methods of treatment of conditions wherein inhibition of the Hepatitis C viral protease is medically indicated, and methods of treatment of a Hepatitis C viral infection in a human patient.
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Page/Page column 66-67

(2010/04/25)

An unusual conformation of α-haloamides due to cooperative binding with zincated porphyrins
CD and NMR spectroscopic evidence of cooperative binding between an α-halogen atom and a carboxamide group with a zinc porphyrin leads to an unprecedented conformation for the determination of the absolute stereochemistry of α-haloamides (α-halocarboxylic acids derivatized with 1,4-phenylenediamine) through the use of exciton-coupled circular dichroism (ECCD). With the use of chiral lactams, whose rotomeric contributions are minimized, both ECCD and NMR spectroscopy demonstrate that the porphyrin favors binding to the side of the sterically more demanding halogen atom as compared to the smaller hydrogen atom. In all, the data is strongly suggestive of an unusual conformation not observed before for α-chiral amides. A mnemonic for determining the absolute stereochemistry of α-halogenated carboxylic acids is provided.
Tanasova, Marina,Yang, Qifei,Olmsted, Courtney C.,Vasileiou, Chrysoula,Li, Xiaoyong,Anyika, Mercy,Borhan, Babak
supporting information; experimental part
p. 4242 - 4253
(2011/02/25)

METHODS AND MATERIALS FOR PREPARING ORGANIC COMPOUNDS FROM PRIMARY AMINES
Methods are disclosed for the conversion of primary amines to other functional groups. The methods can be used to prepare chiral organic compounds, including organic alcohols and organic halides. The methods can be carried out by treating a primary amine with an activating agent and a nitrosyl agent to produce the transformed compound along with nitrous oxide.
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Page/Page column 24-27

(2008/06/13)

New scalable asymmetric aminomethylation reaction for the synthesis of β2-amino acids
β-Amino acids are useful tools in the design of peptidomimetics, and the development of new methods for their syntheses, particularly the synthesis of β2-amino acids, remains an important challenge. Here we report a new scalable route based on the aminomethylation of silyl ketene N,O-acetals by Mannich-type iminium electrophiles. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Moumne, Roba,Denise, Bernard,Guitot, Karine,Rudler, Henri,Lavielle, Solange,Karoyan, Philippe
p. 1912 - 1920
(2008/02/06)

Superparamagnetic nanoparticle-supported enzymatic resolution of racemic carboxylates
Candida rugosa lipase immobilized on maghemite nanoparticles demonstrated high stereoselectivity in kinetic resolution of racemic carboxylates and improved long-term stability over its parent free enzyme, allowing the supported enzyme to be repeatedly used for a series of chiral resolution reactions. The Royal Society of Chemistry 2005.
Gardimalla, Hari M. R.,Mandal, Deendayal,Stevens, Philip D.,Yen, Max,Gao, Yong
p. 4432 - 4434
(2007/10/03)

Fast and chemoselective N-debenzylation route to chiral 2-substituted thiomorpholin-3-ones
Reaction time was found to be the critical parameter for the chemoselective N-debenzylation of thiomorpholin-3-one-derivatives with lithium in ammonia. This paper also reports the first preparation of a chiral 2-substituted thiomorpholine building block.
Franceschini, Nicolas,Da Nascimento, Sophie,Miel, Hugues,Sonnet, Pascal
p. 509 - 512
(2007/10/03)

Diethyl zinc catalyzed diastereoselective addition of ketenes to (S)-(+)-3-hydroxytetrahydrofuran
The reaction of (S)-(+)-3-hydroxytetrahydrofuran with phenyl methyl ketene in presence of n-BuLi and Et2Zn results in the formation of the diastereomeric esters (SS+SR) with a high degree of diastereoselectivity (98:2).
Tandon, Vishnu K.
p. 5985 - 5987
(2007/10/03)

Enantioselective synthesis of α-bromo acid derivatives and bromohydrins from tartrate derived bromoacetals
Bromination of the acetals 4 derived from aryl alkyl ketones, ArCOR, and (2R,3R)-tartaric acid results in bromoacetals 5 with 78-90% de. Hydrolysis of those compounds with Ar = 4-methoxyphenyl or 3-bromo-4-methoxyphenyl results, after recrystallisation, in α-bromoketones 8 with 66-98% ee which are shown to undergo the Baeyer-Villiger oxidation to α-bromoesters 9 with minimal racemisation, α-Bromoketone 8d is shown to undergo carbonyl reduction to threo-bromohydrin 15 with retention of stereochemistry.
Boyes, Scott A.,Hewson, Alan T.
p. 2759 - 2765
(2007/10/03)

(R)- and (S)-3-Hydroxy-4,4-dimethyl-1-phenyl-2-pyrrolidinone as chiral auxiliaries for the asymmetric synthesis of α-hydroxy acids
Rac-α-bromo acids, rac-4, have been converted into(R)- or(S)-α-hydroxy acids, (R)- or (S)-9 by DCC-induced esterification with the chiral auxiliaries (R)or (S)-1, followed by reaction with sodium p-methoxyphenoxide in the presence of tetra-n-hexylammonium iodide, conditions of dynamic kinetic resolution, to give quite diastereoselectively the (αR,3S)- or (αS,3R)-α-(p-methoxyphenoxy) esters, 7, which were then oxidized with eerie ammonium nitrate and hydrolyzed under controlled acid conditions.
Camps, Pelayo,Perez, Francesc,Soldevilla, Nuria
p. 1877 - 1894
(2007/10/03)

Difference in the behavior of methyl (S)-α-bromopropionate in its addition to trimethylvinylsilane depending on the method of initiation
The addition of methyl (S)-2-bromopropionate to trimethylvinylsilane initiated by systems based on iron pentacarbonyl affords a racemic adduct and is accompanied by racemization of the unreacted chiral ester. In the presence of benzoyl peroxide, the reaction proceeds similarly, but no racemization of the starting chiral ester occurs.
Terentiev,Vasilieva,Kuz'mina,Orlova,Ikonnikov,Mysov,Kolehmainen,Laihia,Belokon'
p. 676 - 679
(2007/10/03)

Asymmetric Synthesis of 2-Chloro- and 2-Bromo-alkanoic acids by Halogenation of α-D-Glucofuranose-Derived Silyl Ketene Acetals.
Optically active (S)-2-bromo- and 2-chloro-alkanoic acids 6 and 7 have been obtained via the diastereoselective halogenation of chiral silyl ketene acetals 3a-f, and subsequent saponification of the resulting crude esters.Examples characterized by e.e. values up to 95percent are reported.The diastereoface selectivity is independent of the silyl ketene acetal E/Z configuration.
Angibaud, P.,Chaumette, J. L.,Desmurs, J. R.,Duhamel, L.,Ple, G.,et al.
p. 1919 - 1932
(2007/10/03)

Biosynthesis of the indolizidine alkaloid cyclizidine: incorporation of singly and doubly labelled precursors
Incorporation of CH313C18O2Na and CD3CH213CO2Na into the indolizidine alkaloid cyclizidine 1, produced by Streptomyces species NCIB 11649, shows that the oxygen attached to C-2 is derived intact from acetate and that the cyclopropyl ring is derived from a single intact propionate unit.However, the level and stereochemistry of the incorporation of deuteriated sodium propionate indicates that it undergoes unexpected modification during incorporation into the cyclopropyl ring.
Leeper, Finian J.,Shaw, Susan E.,Satish, Padma
p. 131 - 141
(2007/10/02)

Synthesis and study of new α-haloacid ferroelectric liquid crystal derivatives. MM2 approach to the molecular structure-ferroelectric activity relationship
In order to understand the structural factors that influence ferroelectric properties, three new series (F, Cl, and Br) of chiral naphthalene-ring derived compounds were synthesized, and their ferroelectric properties [spontaneous polarization (Ps) and response time (τ)] were evaluated in the pure compound. The chiral tails are α-halo acids derived from L-α-amino acids: L-α-alanine (1), L-leucine (2), L-isoleucine (3), and L-valine (4), with a fluorine, chlorine, or bromine atom in the chiral center. The highest Ps values were obtained for compounds containing a fluorine or chlorine atom in their asymmetric center and with chiral tail derived from L-isoleucine (3) (F-3, 102 nC/cm2; Cl-3, 100 nC/cm2). The steric requirements of the halogen atom and the bulky alkyl group in the asymmetric center determine the most stable conformations of these chiral tails, which have been studied by molecular mechanic empirical calculations, MM2. MM2 calculations prove to be a successful tool for understanding how the structure of the lateral chiral tail affects molecular arrangement and, as a consequence, the ferroelectric properties of the materials.
Sierra,Serrano,Ros,Ezcurra,Zubía
p. 7645 - 7651
(2007/10/02)

Nucleophilic Substitution Reactions of Alkyl Halides By Using New Polymer-Supported Reagents Containing Hemin
A new polymer reagent consisting of hemin, divinylbenzene, and 2-methyl-5-vinylpyridine was synthesized by suspension copolymerization.Substitution reactions of primary, secondary, and tertiary alkyl halides with the hemin copolymer combined with cyanide, azide, and thiocyanate ions were given satisfactory yields.This reaction mechanism was revealed to be a SNi type on the basis of stereochemical study.The hemin copolymer was not only a polymer-supported reagent with functional capabilities, but also served to separate the product from the reaction mixture.
Saito, Kiyoshi,Harada, Kaoru
p. 2562 - 2566
(2007/10/02)

BIOSYNTHESIS OF THE POLYETHER ANTIBIOTIC MONENSIN-A. RESULTS FROM THE INCORPORATIONS OF LABELLED ACETATE AND PROPIONATE AS A PROBE OF THE CARBON CHAIN ASSEMBLY PROCESSES
The incorporation of sodium - and (S)--propionate into the polyether antibiotic monensin-A in cultures of Streptomyces cinnamonensis occurs with retention of label only at C-4 and C-6, whereas during the incorporation of sodium (R)-propionate the deuterium label is lost to the medium.These results are consistent with the formation of (S)-methylmalonyl-CoA from the labelled propionate by carboxylation of propionyl-CoA with loss of the 2-pro-R hydrogen.The (S)-methylmalonyl-CoA is subsequently incorporated into the antibiotic by a decarboxylative condensation occuring with overall inversion.The incorporations of sodium -and -acetates into monensin-A provide evidence for a pathway of metabolism leading to methylmalonyl-CoA that does not proceed via succinyl-CoA.Instead, acetyl-CoA may be processed via butyryl-CoA and isobutyryl-CoA, to afford (S)-methylmalonyl-CoA.
Sood, Gulshan R.,Ashworth, Doreen M.,Ajaz, Abid A.,Robinson, John A.
p. 3183 - 3194
(2007/10/02)

INHIBITORS OF HUMAN LEUCOCYTE ELASTASE. PEPTIDES INCORPORATING AN &α-AZANORVALINE RESIDUE OR A THIOMETHYLENE LINKAGE IN PLACE OF A PEPTIDE BOND
Peptides containing an α-azanorvaline residue at the C-terminus and N- group at the N-terminus have been made as inhibitors of human leucocyte elastase.A number of analogues with an amide bond replaced by a thiomethylene group have also been prepared.The analogues were tested against leucocyte elastase using MeO-Suc-Ala-Ala-Pro-Val-p-nitroanilide as a substrate and the results were obtained as IC50 values.Both types of analogues inhibited the leucocyte elastase; the most potent of these was N--L-valyl-L-prolyl-α-azanorvaline phenyl ester ( 2 ) ( IC50 0.28 μM, Ki 0.02 μM ).
Dutta, Anand S.,Giles, Michael, B.,Gormley, James J.,Williams, Joseph C.,Kusner, Edward J.
p. 111 - 120
(2007/10/02)

Asymmetric Reduction of Chiral Acetophenone Oxime Ethers to Optically Active Primary Amines
Chiral oxime ethers were synthesized from Na salt of acetophenone oxime and chiral halides, tosylates, or N-tosylaziridines which were derived from β-pinene or α-amino acids.Asymmetric reduction of the chiral oxime ether with LiAlH4 or BH3*THF gave the optically active primary amine.
Itsuno, Shinichi,Tanaka, Kazuo,Ito, Koichi
p. 1133 - 1136
(2007/10/02)

Resolution of Racemic Mixtures via Lipase Catalysis in Organic Solvents
Yeast lipase and porcine pancreatic lipase have been found to vigorously function in nearly anhydrous organic solvents and catalyze the reactions of esterification and transesterification, respectively, in highly stereoselective manner.With use of these enzymatic processes, a number of optically active alcohols, carboxylic acids, and their esters have been prepared on a gram scale.
Kirchner, Gerald,Scollar, Mark P.,Klibanov, Alexander M.
p. 7072 - 7076
(2007/10/02)

STEREOSELEKTIVE SYNTHESE VON D-α-HYDROXYCARBONSAEUREN BZW. D-α-HYDROXYCARBONSAEUREN ENTHALTENDEN DEPSIPEPTIDEN AUS L-AMINOSAEUREN
Depsipeptides containing D-α-hydroxy carboxylic acids are efficiently synthesized by the reactions of L-α-halo-carboxylic acid esters (obtained from L-amino acids) with caesium salts of N-protected amino acids.
Lerchen, Hans-Georg,Kunz, Horst
p. 5257 - 5260
(2007/10/02)

Enantiospecific Synthesis of the trans-9-carbazoles
The compounds in the title, (R,R)- and (S,S)-2, are isomers of the cis-dimethyl compound 1, which is in human trials as an antipsychotic.They were made starting with chiral alanine esters (6) and the 2-bromopropionic esters made from the alanines of opposite chirality (5) and proceeding by cyclization of the ethoxycarbonyl-protected iminodipropionic acids 9, via anhydride 10, with 3-(9-carbazolyl)propylamine and subsequent BH3 reduction of the imides 12 followed by hydrolytic removal of the COOEt.Selection of the reagents necessary to minimize racemization D 20 values at each condensation stage and the 1H and 13C NMR absorption data required for structure proof of 2 are given; a ring inversion rate of 5200 s-1 is calculated based on low and ambient temperature 13C NMR data.
Harfenist, Morton,Hoerr, David C.,Crouch, Ronald
p. 1356 - 1359
(2007/10/02)

Synthesis of the 2-ethyl-3-methylsuccinic acids via a stereospecific malonic ester alkylation
Reaction of (-)-(S)-methyl 2-bromopropionate (4) (obtained from L-alanine) with dibenzyl ethylmalonate gave stereospecifically in four steps (+)-(2R,3S)-2-ethyl-3-methylsuccinic acid (8a) and its diastereoisomer (8b).The malonic ester alkylation proceeded with Walden inversion.The chiroptical properties of the acids and the intermediates are in conformity with the known absolute configurations.
Leeuwen, F. F. van,Noordam, A.,Maat, L.,Beyerman, H. C.
p. 96 - 99
(2007/10/02)