- Kasumigamide, an antialgal peptide from the cyanobacterium Microcystis aeruginosa
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Kasumigamide (1), a novel antialgal tetrapeptide containing an N-terminal α-hydroxy acid, was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-87). Its structure was elucidated by two-dimensional 1H-1H and 1H-13C NMR correlation experiments and confirmed by mass spectral and amino acid analyses. The absolute stereochemistry of 1 was determined by chemical studies. This peptide showed an antialgal activity against the green alga Chlamydomonas neglecta (NIES-439).
- Ishida, Keishi,Murakami, Masahiro
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- Intermolecular Amine Transfer to Enantioenriched trans-3Phenylglycidates by an α/β-Aminomutase to Access Both anti-Phenylserine Isomers
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β-Hydroxy-α-amino acids are noncanonical amino acids with two stereocenters and with useful applications in the pharmaceutical and agrochemical sectors. Here, a 5-methylidene-3,5-dihydro-4H-imidazol-4-one-dependent aminomutase from Taxus canadensis (TcPAM) was repurposed to transfer the amino group irreversibly from (2S)-styryl-α-alanine to exogenously supplied trans-3-phenylglycidate enantiomers, producing anti-phenylserines stereoselectively. TcPAM catalysis inverted the intrinsic regioselective chemistry from amination at Cβ to Cα of enantioenriched trans-3-phenylglycidates to make phenylserine predominantly (97%)phenylisoserine (~3% relative abundance). Gas chromatography?mass spectrometry analysis of the chiral auxiliary derivatives of the biocatalyzed products confirmed that the amine transfer was stereoselective for each glycidate enantiomer. TcPAM converted (2S,3R)-3-phenylglycidate to (2S)-anti-phenylserine predominantly (89%) and (2R,3S)-3-phenylglycidate to (2R)-anti-phenylserine (88%)their antipodes, with inversion of the configuration at Cα in each case. Both glycidate enantiomers formed a small amount (~10%) of syn-phenylserine by retaining the configuration at Cα. The minor syn-isomer likely came from a β-hydroxy oxiranone intermediate formed by intramolecular ring opening of the oxirane ring by the carboxylate before amine transfer. TcPAM had a slight preference toward (2S,3R)-3-phenylglycidate, which was turned(kcat = 0.3 min?1) 1.5 times faster than the (2R,3S)-glycidate (kcat = 0.2 min?1). The catalytic efficiencies (kcatapp/KMapp ≈ 20 M?1s?1) of TcPAM for the antipodes were similar. The kinetic data supported a two-substrate ping-pong mechanism for the amination of the phenylglycidates, with competitive inhibition at higher glycidate substrate concentrations.
- Shee, Prakash K.,Yan, Honggao,Walker, Kevin D.
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p. 15071 - 15082
(2020/12/21)
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- Exploring the scope of an α/β-aminomutase for the amination of cinnamate epoxides to arylserines and arylisoserines
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Biocatalytic process-development continues to advance toward discovering alternative transformation reactions to synthesize fine chemicals. Here, a 5-methylidene-3,5-dihydro-4H-imidazol-4-one (MIO)-dependent phenylalanine aminomutase from Taxus canadensis (TcPAM) was repurposed to irreversibly biocatalyze an intermolecular amine transfer reaction that converted ring-substituted trans-cinnamate epoxide racemates to their corresponding arylserines. From among 12 substrates, the aminomutase ring-opened 3′-Cl-cinnamate epoxide to 3′-Cl-phenylserine 140 times faster than it opened the 4′-Cl-isomer, which was turned over slowest among all epoxides tested. GC/MS analysis of chiral auxiliary derivatives of the biocatalyzed phenylserine analogues showed that the TcPAM-transamination reaction opened the epoxides enantio- A nd diastereoselectively. Each product mixture contained (2S)+(2R)-anti (erythro) and (2S)+(2R)-syn (threo) pairs with the anti-isomers predominating (-90:10 dr). Integrating the vicinal proton signals in the 1H NMR spectrum of the enzyme-catalyzed phenylserines and calculating the chemical shift difference (?"?) between the anti and syn proton signals confirmed the diastereomeric ratios and relative stereochemistries. Application of a (2S)-threonine aldolase from E. coli further established the absolute stereochemistry of the chiral derivatives of the diastereomeric enzymatically derived products. The 2R:2S ratio for the biocatalyzed anti-isomers was highest (88:12) for 3′-NO2-phenylserine and lowest (66:34) for 4′-F-phenylserine. This showed that the stereospecificity of TcPAM is in part directed by the substituent-type on the cinnamate epoxide analogue. The catalyst also converted each cinnamate epoxide analogue to its corresponding isoserine, highlighting a biocatalytic route to arylisoserines, which play a key role in building the pharmacophore seen in anticancer and protease inhibitor drugs.
- Shee, Prakash K.,Ratnayake, Nishanka Dilini,Walter, Tyler,Goethe, Olivia,Onyeozili, Edith Ndubuaku,Walker, Kevin D.
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p. 7418 - 7430
(2019/08/20)
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- Trading N and O. Part 4: Asymmetric synthesis of syn-β-substituted-α-amino acids
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A total of nine enantiopure syn-β-substituted-α-amino acids have been synthesised, comprising both syn-β-hydroxy-α-amino acids and syn-β-fluoro-α-amino acids. The key step in the synthetic strategy towards these syn-β-substituted-α-amino acids involves a stereospecific rearrangement, which proceeds via the intermediacy of the corresponding aziridinium ions. The requisite enantiopure syn-α-hydroxy-β-amino esters were prepared via asymmetric aminohydroxylation of the corresponding α,β-unsaturated esters followed by epimerisation of the resultant anti-α-hydroxy-β-amino esters at the C(2)-position. Subsequent activation of the α-hydroxy moiety as a leaving group followed by displacement by the β-amino substituent gave the corresponding aziridinium species. Regioselective in situ ring-opening of the aziridinium intermediates with either water or fluoride gave the corresponding syn-β-hydroxy-α-amino ester or syn-β-fluoro-α-amino ester, respectively, and N-deprotection and ester hydrolysis afforded the target syn-β-substituted-α-amino acids as single diastereoisomers in good overall yield.
- Davies, Stephen G.,Fletcher, Ai M.,Greenaway, Catherine J.,Kennedy, Matthew S.,Mayer, Christoph,Roberts, Paul M.,Thomson, James E.
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p. 5049 - 5061
(2018/05/08)
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- A new d-threonine aldolase as a promising biocatalyst for highly stereoselective preparation of chiral aromatic β-hydroxy-α-amino acids
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d-Threonine aldolase is an enzyme belonging to the glycine-dependent aldolases, and it catalyzes the reversible aldol reaction of glycine and acetaldehyde to give d-threonine and/or d-allo-threonine. In this study, a putative d-threonine aldolase gene from Delftia sp. RIT313 was cloned and expressed in Escherichia coli BL21 (DE3). The purified enzyme (DrDTA, 47 KDa) exhibited 21.3 U mg-1 activity for the aldol addition of glycine and acetaldehyde in MES-NaOH buffer (pH 6.0) at 50 °C. Both pyridoxal 5′-phosphate and metal ions were needed for the reaction, and the existence of the metal ions enhanced the stability of the enzyme. It was found that the conversion and Cβ-stereoselectivity were dramatically influenced by the reaction temperature, co-solvent, amount of enzyme and reaction time, and it is possible to enable the reaction under kinetic control to retain suitable conversion and high stereoselectivity at the β-carbon, thus tackling the "Cβ-stereoselectivity problem". DrDTA showed high activity toward aromatic aldehydes with electron-withdrawing substituents. Under the optimized reaction conditions, phenylserines with a 2′-fluoro- or 3′-nitro-substituent were obtained with >90% conversion and >90% de. In addition, dl-threo-phenylserine and dl-threo-4-(methylsulfonyl)phenylserine were efficiently resolved with an excellent enantiomeric excess value (ee, >99%) using a whole cell biocatalyst in a two-phase system at 1.0 M and 0.3 M, respectively, the highest substrate concentration reported so far. These results suggested that DrDTA might be a promising biocatalyst for producing chiral aromatic β-hydroxy-α-amino acids.
- Chen, Qijia,Chen, Xi,Cui, Yunfeng,Ren, Jie,Lu, Wei,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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p. 5964 - 5973
(2017/12/26)
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- METHOD FOR SYNTHESIZING OPTICALLY ACTIVE a-AMINO ACID USING CHIRAL METAL COMPLEX COMPRISING AXIALLY CHIRAL N-(2-ACYLARYL)-2-[5,7-DIHYDRO-6H-DIBENZO[c,e]AZEPIN-6-YL] ACETAMIDE COMPOUND AND AMINO ACID
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Objects of the present invention are to provide an industrially applicable method for producing an optically active α-amino acid in high yield and in a highly enantioselective manner, to provide a simple production method of an optically active α,α-disubstituted α-amino acid, and to provide an intermediate useful for the above production methods of an optically active α-amino acid and an optically active α,α-disubstituted α-amino acid. The present invention provides a production method of an optically active α-amino acid or a salt thereof, the production method comprising introducing a substituent into the α carbon in the α-amino acid moiety of a metal complex represented by the following Formula (1): by an alkylation reaction, an aldol reaction, the Michael reaction, or the Mannich reaction, and releasing an optically pure α-amino acid enantiomer or a salt thereof by acid decomposition of the metal complex.
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Paragraph 0385-0390
(2016/05/10)
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- METHOD FOR SYNTHESIZING OPTICALLY ACTIVE α-AMINO ACID USING CHIRAL METAL COMPLEX COMPRISING AXIALLY CHIRAL N-(2-ACYLARYL)-2-[5,7-DIHYDRO-6H-DIBENZO[c,e]AZEPIN-6-YL]ACETAMIDE COMPOUND AND AMINO ACID
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Objects of the present invention are to provide an industrially applicable method for producing an optically active ±-amino acid in high yield and in a highly enantioselective manner, to provide a simple production method of an optically active ±,±-disubstituted ±-amino acid, and to provide an intermediate useful for the above production methods of an optically active ±-amino acid and an optically active ±,±-disubstituted ±-amino acid. The present invention provides a production method of an optically active ±-amino acid or a salt thereof, the production method comprising introducing a substituent into the ± carbon in the ±-amino acid moiety of a metal complex represented by the following Formula (1): by an alkylation reaction, an aldol reaction, the Michael reaction, or the Mannich reaction, and releasing an optically pure ±-amino acid enantiomer or a salt thereof by acid decomposition of the metal complex.
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Paragraph 0647; 0649; 0650; 0659
(2016/11/17)
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- Biocatalytic Synthesis of Enantiopure β-Methoxy-β-arylalanine Derivatives
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Chiral β-hydroxy-β-arylalanine and β-methoxy-β-arylalanine derivatives, which occur widely in marine nature products, were stereoselectively synthesized with 99 % ee values. The two erythro isomers were prepared by L- or D-aminoacylase-catalyzed resolution of the corresponding N-acetyl derivatives, whereas the two threo isomers were obtained only by D-aminoacylase-catalyzed resolution of the derivatives. erythro-β-Hydroxy-β-arylalanine derivatives were prepared by diastereoselective hydrogenation of ethyl 2-(hydroxyimino)-3-oxo-3-arylpropanoates, which were in turn acquired by the oximation of ethyl 3-oxo-3-arylpropanoates with ethyl nitrite in the presence of nano-K2CO3 with yields of 72 % to 80 %. β-Methoxy-β-arylalanine derivatives were synthesized through Williamson reactions between the corresponding β-hydroxy-β-arylalanines and iodomethane with silver oxide as base.
- Fan, Shiming,Liu, Shouxin,Zhang, Hubo,Liu, Ying,Yang, Yihuang,Jin, Longyi
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p. 5591 - 5597
(2014/10/15)
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- Diastereo- And enantioselective synthesis of β-Hydroxy-α-amino acids: Application to the synthesis of a key intermediate for lactacystin
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The development of a highly efficient and stereoselective methodology for the preparation of β-hydroxy-α- amino acids is described. Nucleophilic addition of enolates of tricyclic iminolactones 1a and 1b to aldehydes in the presence of 6 equiv of lithium chloride in THF at -78 °C leads to aldol adducts in good yield (63-86%) and high diastereoselectivity (up to >25:1 dr). Subsequently, hydrolysis of the aldol adducts under acidic conditions leads to the corresponding β-hydroxy-a-amino acids in good yields (up to 83%) and excellent enantiomeric excesses (99% ee) with good recovery yields of the chiral auxiliaries 6 and 7. This methodology was applied to the facile synthesis of the key intermediate for lactacystin along with several isomers.
- Li, Qiong,Yang, Shao-Bo,Zhang, Zhihui,Li, Lei,Xu, Peng-Fei
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supporting information; experimental part
p. 1627 - 1631
(2009/09/24)
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- Synthesis of β-hydroxy-α-amino acids with a reengineered alanine racemase
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The Y265A mutant of alanine racemase (alrY265A) was evaluated as a catalyst for the synthesis of β-hydroxy-α-amino acids. It promotes the PLP-dependent aldol condensation of glycine with a range of aromatic aldehydes. The desired products were obtained wi
- Fesko, Kateryna,Giger, Lars,Hilvert, Donald
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supporting information; experimental part
p. 5987 - 5990
(2009/06/25)
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- Threonine aldolases-an emerging tool for organic synthesis
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In a systematic study, 21 ring-substituted benzaldehydes were reacted with glycine under catalysis with a l-threonine aldolase (lTA) from Pseudomonas putida and a d-threonine aldolase (dTA) from Alcaligenes xylosoxidans to form the corresponding β-hydroxy-α-amino acids 1-18. dTA proved to be highly selective with ee's >99% (d) and de's up to 99% (syn). Two thiamphenicol precursors were synthesized utilizing dTA on a preparative scale. lTA-catalyzed reactions led to ee's >99% (l) but low to moderate de's (20-50%, syn).
- Steinreiber, Johannes,Fesko, Kateryna,Reisinger, Christoph,Schürmann, Martin,van Assema, Friso,Wolberg, Michael,Mink, Daniel,Griengl, Herfried
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p. 918 - 926
(2007/10/03)
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- An enantioselective synthesis of nitrogen protected 3-arylserine esters
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A method for the preparation of (2R,3S) nitrogen protected arylserine esters is described. The method consists of rhodium mediated insertion of tert-butylcarbamate into the corresponding 3-keto-2-diazoester, affording the N-protected α-amino-β-ketoester, followed by asymmetric reduction/dynamic resolution to afford the corresponding N-protected 3-arylserine esters in good chemical yield, and in most cases high enantiomeric excess.
- Bourdon, Lisa H.,Fairfax, David J.,Martin, Gregory S.,Mathison, Casey J.,Zhichkin, Pavel
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p. 3485 - 3487
(2007/10/03)
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- Catalytic enantio- and diastereoselective aldol reactions of glycine-derived silicon enolate with aldehydes: An efficient approach to the asymmetric synthesis of anti-β-hydroxy-α-amino acid derivatives
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We have developed an efficient method for the asymmetric synthesis of anti-β-hydroxy-α-amino acid derivatives based on highly enantio- and diastereoselective aldol reactions of the silicon enolate derived from N-trifluoroacetylglycinate with aldehydes using a chiral zirconium catalyst. The resulting N-trifluoroacetyl group is easily cleaved under either acidic or basic conditions and can be used directly as a protecting group for further transformations. Copyright
- Kobayashi, Jun,Nakamura, Masayuki,Mori, Yuichiro,Yamashita, Yasuhiro,Kobayashi, Shu
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p. 9192 - 9193
(2007/10/03)
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- Gymnangiamide, a Cytotoxic Pentapeptide from the Marine Hydroid Gymnangium regae
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A cytotoxic aqueous extract from the marine hydroid Gymnangium regae provided a novel linear pentapeptide, designated gymnangiamide (1). The planar structure of 1 was elucidated by interpretation of spectral data as well as chemical degradation and derivatization studies. In addition to the amino acids isoleucine and phenylserine, this peptide contained N-desmethyldolaisoleuine, O-desmethyldolaproine, and α-guanidino serine, three residues that have not previously been reported in a natural product. The absolute configurations of the constituent amino/guanidino acids were determined by chemical degradation and derivatization, followed by HPLC and LC-MS comparison with authentic standards. Gymnangiamide (1) was moderately cytotoxic against a number of human tumor cell lines in vitro.
- Milanowski, Dennis J.,Gustafson, Kirk R.,Rashid, Mohammad A.,Pannell, Lewis K.,McMahon, James B.,Boyd, Michael R.
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p. 3036 - 3042
(2007/10/03)
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- Preparation of optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (threo-beta-phenylserine) via optical resolution.
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To obtain optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (1), (2RS,3SR)-2-benzoylamino-3-hydroxy-3-phenylpropanoic acid [(2RS,3SR)-2] was first optically resolved using (1S,2S)- and (1R,2R)-2-amino-1-(4-nitrophenyl)-1,3-propanediol as the resolving agents to afford (2R,3S)- and (2S,3R)-2 in yields of 73% and 66%, based on half of the starting amount of (2RS,3SR)-2. Next, the racemic structures of ammonium and some organic ammonium salts of (2RS,3SR)-2 were examined based on melting point, solubility, and infrared spectrum, with the aim of optical resolution by preferential crystallization. The benzylammonium salt of (2RS,3SR)-2 was suggested to exist as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization of the racemic salt afforded the (2R,3S)- and (2S,3R)-salts with optical purities of 90-97%. The (2R,3S)- and (2S,3R)-2 obtained from the purified salts were hydrolyzed by reflux in hydrochloric acid to give (2R,3S)- and (2S,3R)-1.
- Shiraiwa, Tadashi,Saijoh, Reiichi,Suzuki, Masahiro,Yoshida, Kyosuke,Nishimura, Satoshi,Nagasawa, Hisashi
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p. 1363 - 1367
(2007/10/03)
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- Synthesis of all stereoisomers and some congeners of isocytoxazone
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cis-Isocytoxazone 2a and trans-isocytoxazone 2b, structural isomers of the antiasthmatic agent cytoxazone (-)-1, and their 5-substituted congeners 23-28 have been prepared. Aldol reaction of para-substituted benzaldehydes with 7-chloro-1-methyl-5-phenyl-1,4-benzodiazepin-2-one, followed by separation of diastereomeric racemates afforded 3-10. Acid-catalyzed 1,4-benzodiazepine ring opening, and transformation of the methyl esters of β-aryl-β-hydroxy-α-amino acids (11-16) via 4-methoxycarbonyl derivatives of 1,3-oxazolidin-2-one (17-22) and their reduction afforded the target oxazolidin-2-one derivatives 23-28. Racemic isocytoxazones 2a and 2b were prepared by an independent route starting from 4-methoxystyrene epoxide. Pure enantiomers of these diastereomeric racemates were separated by HPLC chromatography on chiral stationary phases. Their CD spectra, along with those of previously prepared enantiomers of cis-cytoxazone 1a and trans-cytoxazone 1b are discussed.
- Hamer?ak, Zdenko,?epac, Dragan,?iher, Dinko,?unji?, Vitomir
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p. 375 - 382
(2007/10/03)
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- Peptide inhibitors of CDK2-cyclin A that target the cyclin recruitment-Site: Structural variants of the C-Terminal Phe
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A focused series of octapeptides based on the lead compound H-His-Ala-Lys-Arg-Arg-Leu-Ile-Phe-NH2 1, in which the C-terminal phenylalanine residue was replaced by α and/or β-modified variants, was synthesized using solid-phase chemistry. Both the L-threo-β-hydroxy-phenylalanine (β-phenylserine, Pse) and (2S)-phenylalaninol derivatives, as competitive binders at the cyclin-recruitment site, displayed potent inhibitory activity towards the CDK2-cyclin A complex. Unexpectedly, the D-threo-Pse derivatives also showed inhibitory activity.
- Atkinson, Gail E.,Cowan, Angela,McInnes, Campbell,Zheleva, Daniella I.,Fischer, Peter M.,Chan, Weng C.
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p. 2501 - 2505
(2007/10/03)
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- A new synthesis of enantiomerically pure syn-(S)-β-hydroxy-α-amino acids via asymmetric aldol reactions of aldehydes with a homochiral Ni(II)-glycine/(S)-BPB Schiff base complex
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syn-(S)-β-Hydroxy-α-amino acids were synthesised stereoselectively via elaboration of the asymmetric aldol reactions of aldehydes with a chiral Ni(II)-(S)-BPB/glycine Schiff base complex in the presence of equimolar NaH in THF. The stereoselectivity of the reaction was studied as a function of time, the reaction conditions, the nature of the carbonyl compounds and the base used. The synthetic potential of this asymmetric method was demonstrated in the preparation of syn-(S)-β-hydroxyleucine on a multi-gram scale.
- Belokon, Yuri N.,Kochetkov, Konstantin A.,Ikonnikov, Nikolai S.,Strelkova, Tatiana V.,Harutyunyan, Syuzanna R.,Saghiyan, Ashot S.
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p. 481 - 485
(2007/10/03)
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- syn/anti Diastereoselectivity in the aldol reaction of aldehydes with the C(3) carbanion of 1,3-dihydro-2H-1,4-benzodiazepin-2-one
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The aldol reaction of the C(3) carbanion of 7-chloro-1,3-dihydro-1- methyl-5-phenyl-2H-1,4-benzodiazepin-2-one (2) with a series of aromatic and aliphatic aldehydes at -78°afforded threo/erythro diastereoisomers 3-16 of 7-chloro-1,3-dihydro-3-(hydroxymethyl)-1-methyl-5-phenyl-2H-1,4- benzodiazepinones, substituted at the C(3) side chain, in a ratio from 55:45 to 94:6 (Scheme 1). Lewis acids exhibited limited effect on the syn/anti diastereoselectivity of this reaction, and kinetic control of the reaction was confirmed. 1H-NMR Data suggested the assignment of the threo relative configuration to the first-eluted diastereoisomers 3, 5 7, and 9 on reversed- phase HPLC, and the erythro configuration to the second-eluted counterparts 4, 6, 8, and 10, respectively. The structures and relative configurations threo and erythro of the diastereoisomers 5 and 6, respectively, were established by single-crystal X-ray analysis, confirming the assignment based on the 1H-NMR data. A tentative mechanistic explanation of the diastereoselectivity invokes the enolate anion of 1,3-dihydro-2H-1,4- benzodiazepin-2-one as the reactive species (Scheme 2). Acid-catalyzed hydrolytic ring opening of 3 afforded threo-β-hydroxy-phenylalanine 17, whereas from 4, the N-(benzyloxy)carbonyl derivative 18 of erythro-β- hydroxy-phenylalanine was obtained (Scheme 3); in both cases, neither elimination of H2O from the C(3)-CHOH moiety nor epimerization at C(3) were observed. This result opens a new pathway to various configurationally uniform α-amino-β-hydroxy carboxylic acids and their congeners of biological importance.
- Markovic, Dean,Hamersak, Zdenko,Visnjevac, Aleksandar,Kojic-Prodic, Biserka,Sunjic, Vitomir
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p. 603 - 615
(2007/10/03)
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- Novel synthesis of 4-carboxymethyl 5-alkyl/aryl oxazolidin-2-ones by rearrangement of 2-carboxymethyl 3-alkyl/aryl N-tert-butoxycarbonyl aziridines
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(matrix presented) A two-step approach for the diastereoselective synthesis of 4-carboxymethyl 5-alkyl/aryl oxazolidin-2-ones is described, which proceeds via the intermediate formation of 2-carboxymethyl 3-alkyl/aryl N-tert-butoxycarbonyl (N-Boc) aziridines. By reaction of N-Boc β-amino methyl esters with LiHMDS and iodine, trans 2,3-disubstituted N-Boc aziridines are obtained with high stereoselectivities and yields. The final rearrangement to oxazolidin-2-ones is achieved by treatment with a catalytic amount of a Lewis acid and proceeds with high yield and complete regio- and stereoselectivity.
- Tomasini, Claudia,Vecchione, Andrea
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p. 2153 - 2156
(2008/02/09)
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- Enantioselective synthesis of cis-2-oxazoline-4-carboxylates by Lewis acid catalyzed formal [3+2] cycloadditions of 5-alkoxyoxazoles with aldehydes
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Formal [3+2] cycloaddition of 2-o-methoxyphenyl-5-methoxyoxazole with benzaldehyde, m- and p-substituted benzaldehydes in the presence of 30 mol% of (R)-methylaluminum β-binaphthoxide, which was prepared from (R)-2,2'-dihydroxy-1,1'-dinaphthyl and 1.1 - 1.05 equiv. of trimethylaluminum, gave cis-2-oxazoline-4-carboxylates in high enantoselectivity.
- Suga, Hiroyuki,Ikai, Kosei,Ibata, Toshikazu
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p. 869 - 872
(2007/10/03)
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- Preparation and use in amino acid synthesis of a new chiral glycine derivative - (R)- and (S)-tert-Butyl 2-tert-Butyl-4-methoxy-2,5-dihydroimidazole-1-carboxylate (BDI)
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The title compound BDI is prepared on multigram scale, either by resolution of the precursor 2-tert-butylimidazolidin-4-one (from glycine amide and pivalaldehyde) through diastereomeric salts (Scheme 2) or by preparative chromatographic enantiomer separation on a chiral column. Lithiated BDI derivatives are highly nucleophilic species, combining the structural elements of a Li enaminate, of an enolether and of an N-Boc-enaminate (E, G). They react with complete diastereoselectivity (NMR analysis) from the face trans to the tert-butyl group. The electrophiles employed are primary and secondary alkyl, allyl, benzyl, and propargyl halides (Schemes 3 and 5), enoates (in Michael additions, Scheme 7), as well as aliphatic and aromatic aldehydes (in aldol additions, Scheme 8). When a third, exocyclic, stereocenter is formed in these reactions, there is a high degree of enantiomer differentiation (with tac. sec. halides, products 10-12) and of enantiotopic face differentiation (with enoates and aldehydes, products 40-50). The reactions are so clean that highly efficient in-situ double alkylations are feasible, in which the sequence of addition of the two different electrophiles determines the configuration at the newly formed stereogenic center (Scheme 5). In contrast to derivatives of previously reported chiral glycine reagents, the products from BDI are converted to methyl esters of amino acids under mild conditions and without concomitant formation (... and the need for recovery or removal) of a chiral auxiliary; the method is compatible with acid-sensitive side chains in the α-amino acids and α-branched α-amino acids to be synthesized (Schemes 4 and 6). The addition of Li-BDI to aldehydes furnishes, after hydrolysis, α-amino-β-hydroxy acids of erythro configuration (allo-threonine analogs, Scheme 8); a model for the stereochemical course of this reaction (rel. topicity unlike) is proposed, and compared with the corresponding conversions of analogous oxazolidinone and imidazolidinone Li enolates which occur with rel. topicity like.
- Seebach, Dieter,Hoffmann, Matthias
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p. 1337 - 1351
(2007/10/03)
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- Stereocontrolled Conversion of L-Serine into a Series of Valuable Unnatural α-Amino Acids
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Stereocontrolled synthesis of (2R,3S)- and (2R,3R)-phenylserine, (R)-3,3-diphenylserine and (R)-3,3-diphenylalanine are described.
- Koskinen, Ari M. P.,Hassila, Heikki,Myllymaeki, Vesa T.,Rissanen, Karl
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p. 5619 - 5622
(2007/10/02)
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- Synthesis, resolution and absolute configuration determination of (S)- and (R)-4-formyl-5-hydroxyparacyclophane and its application in the asymmetric synthesis of α-amino acids
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Racemic (R,S)-4-formyl-5-hydroxyparacyclophane (FHPC) was resolved into enantiomers via its Schiff's base with (S)- and (R)-α-phenylethylamine (α-PEAM) and its absolute configuration was determined by an X-ray diffraction structural study.Scalemic FHPC or its derivatives can be used as chiral auxiliaries for the asymmetric synthesis of β-hydroxy-α-amino acids and α-methylphenylalanine with ees ranging mostly from 45 to 98percent.
- Antonov, Dmitri Yu.,Belokon, Yuri N.,Ikonnikov, Nikolai S.,Orlova, Svetlana A.,Pisarevsky, Aleksander P.,et al.
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p. 1873 - 1880
(2007/10/02)
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- Preparation of (2R,3S)-β-hydroxy-α-amino acids by use of novel Streptomyces aldolase as a resolving agent for racemic material
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A unique aldolase, which was isolated from Streptomyces amakusaensis, is used to catalyse a reverse aldol reaction on representative racemic β-hydroxy-α-amino acids (3-6) to give samples of the (2R,3S)-(D-threo)-enantiomers with excellent enantiomeric purity.
- Herbert, Richard B.,Wilkinson, Barrie,Ellames, George J.
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p. 114 - 117
(2007/10/02)
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- Stereoselective Synthesis of β-Phenylserine from Glycine and Benzaldehyde as Mediated by Catalytic Bilayer Membranes, Artificial Vitamin B6-dependent Enzymes
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The aldolation of glycine with benzaldehyde to yield β-phenylserine was catalyzed by supramolecular assemblies formed with a synthetic peptide lipid, a hydrophobic vitamin B6 derivative, and zinc(II) ions in aqueous media under mild conditions.A diastereomeric ratio of the reaction products was much dependent on a size and a phase property of the vesicular catalyst.
- Kikuchi, Jun-ichi,Takashima, Toru,Nakao, Hidetoshi,Hie, Ken-ichi,Etoh, Hiroshi,et al.
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p. 553 - 556
(2007/10/02)
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- General Method for the Synthesis of Enantiomerically Pure β-Hydroxy-α-amino Acids, containing Fluorine Atoms in the Side Chains. Case of Stereochemical Distinction between Methyl and Trifluoromethyl Groups. X-Ray Crystal and Molecular Structure of the Nickel(II) Complex of ...
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The chiral NiII complex 1 of a Schiff's base derived from (S)-o-benzophenone (BPB) and glycine was treated with fluoro-substituted aldehydes (aliphatic and aromatic) in MeOH or CHCl3.The addition proceeds with high diastereoselectivity to give, if catalysed by MeONa in MeOH, the corresponding complexes of syn-(2R)-3-fluorophenylserines (84-100percent) d.e.) and syn-(2S)-fluoroalkylserines (90percent d.e.), and, if catalysed by NEt3 or DABCO (MeOH or CHCl3), the corresponding complexes of syn-(2S)-, and anti-(2S)-3-fluorophenylserines and fluoroalkylserines.The second-order asymmetric transformation may be successfully employed to obtain diastereoisomerically pure complexes of anti-(2R)-3-fluorophenylserines.Condensation of trifluoroacetone with complex 1, catalysed by MeONa, gave predominantly (at least >95percent d.e.) the diastereoisomeric complex, containing (2S,3S)-β-(trifluoromethyl)threonine, as shown by an X-ray diffraction structural study.Diastereoisomerically and enantiomerically pure fluorine-containing 3-phenyl- and 3-alkyl-serines were obtained from the corresponding diastereomerically pure complexes, separated by chromatography or crystallization.The initial chiral auxiliary BPB was recovered (80-98percent).The influence of the reaction's conditions and the nature of the corresponding fluoro-substituted aldehydes on the diastereoselectivity of the reactions is discussed.
- Soloshonok, Vadim A.,Kukhar, Valeri P.,Galushko, Sergei V.,Svistunova, Nataly Yu.,Avilov, Dimitri V.,et al.
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p. 3143 - 3156
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF HETEROORGANIC ANALOGS OF NATURAL COMPOUNDS. 3. GENERAL PREPARATIVE METHOD OF DIASTEREO- AND ENANTIOSELECTIVE SYNTHESIS OF FLUORINE-CONTAINING 2(R),3(S)-β-PHENYLSERINES
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The diastereo- and enantioselective synthesis of the previously unknown 2(R),3(S)-β-phenylserines containing fluorine atoms, the O-CHF2-, O-CF3-, and CF3 groups in the benzene ring, was carried out by alkylation of a Ni(II) complex of a Schiff base of glycine with (S)-2-N-(N'-benzylprolyl)aminobenzophenone by fluorine-substituted benzaldehydes.The factors influencing the stereochemical result of the reactions studied are not the steric characteristics of the substituents in benzaldehydes, but their electronic nature.
- Soloshonok, V. A.,Kukhar, V. P.,Galushko, S. V.,Kolycheva, M. T.,Rozhenko, A. B.,Belokon, Yu. N.
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p. 1046 - 1054
(2007/10/02)
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- 142. Praeparative chromatographische Enantiomerentrennung von synthetisch nuetzlichen cyclischen Acetalen
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Preparative Chromatographic Resolution of Sunthetically Useful Cyclic Acetals Racemic cyclic acetals derived from aldehydes and glycine, glycolic acid, thioglycolic acid, formylacetic acid, and acetoacetic acid (oxazolidinones 4-13, dioxolanones 14,15, ox
- Seebach, Dieter,Mueller, Stefan G.,Gysel, Urs,Zimmermann, Juerg
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p. 1303 - 1318
(2007/10/02)
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- DIBENZYLAMINOACETATES AS USEFUL SYNTHETIC EQUIVALENTS OF GLYCINE IN THEi SYNTHESIS OF α-AMINO-β-HYDROXYACIDS
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The stereochemical course of three new simple methodologies for the preparation of α-amino-β-hydroxyacids starting from dibenzylaminoacetates as synthetic equivalents of glycine is described.While the aldol-type condensation via lithium enolates gave results highly dependent on the aldehyde employed, producing in some cases diastereoselectivities up to 5:1 for the anti isomers, the acid-catalysed aldol condensation of silyl ketene acetals yielded predominantly syn adducts with selectivities from 5:1 to 32:1.Finally the acylation-reduction procedure gave the best results in terms of yields and stereoselectivities, affording syn isomers with excellent induction ( 13:1).
- Guanti, Giuseppe,Banfi, Luca,Narisano, Enrica,Scolastico, Carlo
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p. 3671 - 3684
(2007/10/02)
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