- Zinc-mediated carbon radical addition to glyoxylic imines in aqueous media for the synthesis of α-amino acids
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The addition of carbon radicals to glyoxylic imines was studied using zinc dust as a radical initiator. The zinc-mediated radical reaction of glyoxylic oxime ethers and hydrazones proceeded smoothly to give the alkylated products via a carbon-carbon bond-
- Ueda, Masafumi,Miyabe, Hideto,Sugino, Hisako,Naito, Takeaki
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Read Online
- Synthesis and solid-phase application of suitably protected γ-hydroxyvaline building blocks
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(Chemical Equation Presented) Recently, an unexpected modified residue, γ-hydroxy-D-valine (D-Hyv), was identified within ribosomally expressed polypeptide chains of four conopeptides from the venoms of Conus gladiator and Conus mus. To assemble Hyv-conta
- Cudic, Mare,Mari, Frank,Fields, Gregg B.
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Read Online
- Design and synthesis of novel symmetric fluorene-2,7-diamine derivatives as potent hepatitis C virus inhibitors
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Hepatitis C virus (HCV) is an international challenge. Since the discovery of NS5A direct-acting antivirals, researchers turned their attention to pursue novel NS5A inhibitors with optimized design and structure. Herein we explore highly potent hepatitis C virus (HCV) NS5A inhibitors; the novel analogs share a common symmetrical prolinamide 2,7-diaminofluorene scaffold. Modification of the 2,7-diaminofluorene backbone included the use of (S)-prolinamide or its isostere (S,R)-piperidine-3-caboxamide, both bearing different amino acid residues with terminal carbamate groups. Compound 26 exhibited potent inhibitory activity against HCV genotype (GT) 1b (effective concentration (EC50) = 36 pM and a selectivity index of >2.78 × 106). Compound 26 showed high selectivity on GT 1b versus GT 4a. Interestingly, it showed a significant antiviral effect against GT 3a (EC50 = 1.2 nM). The structure-activity relationship (SAR) analysis revealed that picomolar inhibitory activity was attained with the use of S-prolinamide capped with R- isoleucine or R-phenylglycine residues bearing a terminal alkyl carbamate group.
- Mousa, Mai H. A.,Ahmed, Nermin S.,Schwedtmann, Kai,Frakolaki, Efseveia,Vassilaki, Niki,Zoidis, Grigoris,Weigand, Jan J.,Abadi, Ashraf H.
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- Enantioselective inclusion of pyrene-1-sulfonate salts of α-amino acids with crystals of α-cyclodextrin
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Enantioselective inclusion of α-amino acids with crystals of α-cyclodextrin (α-CD) has been achieved by converting the amino acids into sulfonate salts with pyrene-1-sulfonic acid (PyS). For example, crystals of α-CD selectively include L-leucine/PyS (1:1) salt in a host/guest ratio of ~1 with 92%ee from a solution of the racemic salt in ethanol/N-methylformamide (91:9) at 40 °C. Under conditions optimized for individual amino acids, the PyS salts of valine, phenylalanine, and methionine are also included with good enantioselectivities (up to 86%ee). Mechanistic studies for the inclusion of leucine/PyS salt reveals that the enantioselectivity originates from the difference in stability between the inclusion complexes of D- and L-leucine/PyS salts with α-CD in crystals.
- Hattori, Tetsutaro,Kitamoto, Yuichi,Maeda, Tetsuya,Miyoshi, Ikuko,Morohashi, Naoya
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supporting information
(2020/04/01)
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- Chiral tetraaryl-and tetraalkynylborates as chiral solvating agents for tetraalkylammonium salts
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The application of tetracarbon-substituted chiral borate sodium salts (NaBR*4) as NMR chiral solvating agents for various tetraalkylammonium salts (R4NX) has been successfully demonstrated. Ion exchange between R4NX and NaBR*4 proceeded in excellent yields and provided the corresponding dia-stereomeric salts (R4NBR*4). The ee values of the R4NX salts were determined by1H NMR analysis of R4NBR*4. Two types of chiral borates, tetraaryl-and tetraalkynylborates with optically active 1,1′-binaphthyl components were used. At the beginning of this research, we investigated the efficacy of a known chiral tetraar-ylborate developed by Pommerening et al. for R4NX. To expand the possibility of further structural design of the chiral borate, we designed chiral tetraalkynylborates as a new structure. Their synthesis and application are also described.
- Tayama, Eiji,Sugawara, Takeshi
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p. 803 - 811
(2019/01/18)
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- Expanding the chemical space of anti-HCV NS5A inhibitors by stereochemical exchange and peptidomimetic approaches
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Here we report a series of potent anti-HCV agents bearing a symmetrical benzidine l-prolinamide backbone with different capping groups including alkyl/aryl carbamates of natural and unnatural valine and leucine amino acids. All compounds were investigated for their inhibitory activity in an HCV replicon assay on genotype 1b. The novel compounds share some chemical and clinical attributes of commercially available NS5A inhibitors. Compounds 5 and 6 with unnatural capping residue and ethyl and isobutyl carbamates showed EC50 values in the picomolar range with a low toxicity profile and selectivity indices of several orders of magnitude. These findings enlarge the chemical space from which NS5A inhibitors may be discovered by adopting unnatural amino acids, amino acids other than valine and carbamates other than methyl as the capping groups.
- Ramsis, Triveena M.,Abdel Karim, Shereen E.,Vassilaki, Niki,Frakolaki, Efseveia,Kamal, Ahmed A. M.,Zoidis, Grigoris,Ahmed, Nermin S.,Abadi, Ashraf H.
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- HETEROCYCLIC UREA DERIVATIVES AND METHODS OF USE THEREOF
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Compounds of formula (IA) and their pharmaceutically acceptable salts are described. Processes for their preparation, pharmaceutical compositions containing them, their use as medicaments and their use in the treatment of bacterial infections are also described.
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Page/Page column 92
(2010/12/29)
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- A bismuth(III)-catalyzed friedel-crafts cyclization and stereocontrolled organocatalytic approach to (-)-platensimycin
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A high yielding route to the (-)-platensimycin core is communicated. This entailed the discovery of Bi(OTf)3 to catalyze a Friedel-Crafts cyclization of a free lactol, supplemented by LiClO4 to suppress the Lewis basicity of the sulfonate group. After TBAF-promoted cyclodearomatization, a diastereoselective conjugate reduction of a dienone was achieved by adopting amine-based organocatalytic rationales to reverse the inherent steric control of the substrate.
- Eey, Stanley T.-C.,Lear, Martin J.
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supporting information; experimental part
p. 5510 - 5513
(2011/03/18)
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- Synthesis and structure-activity relationship of a novel series of heterocyclic sulfonamide γ-secretase inhibitors
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γ-Secretase inhibitors have been shown to reduce the production of β-amyloid, a component of the plaques that are found in brains of patients with Alzheimer's disease. A novel series of heterocyclic sulfonamide γ-secretase inhibitors that reduce β-amyloid levels in cells is reported. Several examples of compounds within this series demonstrate a higher propensity to inhibit the processing of amyloid precursor protein compared to Notch, an alternative γ-secretase substrate.
- Pu, Jun,Kreft, Anthony F.,Aschmies, Suzan H.,Atchison, Kevin P.,Berkowitz, Joshua,Caggiano, Thomas J.,Chlenov, Micheal,Diamantidis, George,Harrison, Boyd L.,Hu, Yun,Huryn, Donna,Steven Jacobsen,Jin, Mei,Lipinski, Kerri,Lu, Peimin,Martone, Robert L.,Morris, Koi,Sonnenberg-Reines, June,Riddell, Dave R.,Sabalski, Joan,Sun, Shaiu-Ching,Wagner, Erik,Wang, Yiqun,Xu, Zheng,Zhou, Hua,Resnick, Lynn
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experimental part
p. 4708 - 4717
(2009/10/23)
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- A Stereoselective entry into functionalized 1,2-diamines by zinc-mediated homologation of α-aminoacids
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A general, stereoselective synthsis of 4,5-disubstituted imidazolidines-2-ones from α-aminoacids has been developed: the key steps are a Biaise reaction of bromoacetate on α-aminonitriles and further reduction. Although reduction with sodium cyanoborohydride afforded a mixture of cis and trans isomers 6a-e with moderate to good stereoselectivity, reduction with sodium in liquid ammonia gave the trans isomers 8a-e with complete stereoselectivity. Acidic hydrolysis of the urea gave 4-amino-pyrrolidinones, which can be precursors to β,γ-diaminoacids or 3-aminopyrrolidines.
- Hoang, Cam Thuy,Alezra, Valerie,Guillot, Regis,Kouklovsky, Cyrille
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p. 2521 - 2524
(2008/02/05)
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- Diastereoselective cationic tandem cyclizations to N-heterocyclic scaffolds: Total synthesis of (-)-dysibetaine PP
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Herein, we report a short and diastereoselective synthesis of the natural product (-)-dysibetaine PP. The key step in the synthetic sequence is a novel highly diastereoselective tandem-cyclization reaction of an enantiomerically pure dipeptide. This cyclization methodology is applied in the synthesis of a broader range of N-heterocyclic scaffolds.
- IJzendoorn, Denis R.,Botman, Peter N. M.,Blaauw, Richard H.
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p. 239 - 242
(2007/10/03)
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- Asymmetric hydrogenation of N-sulfonylated-α-dehydroamino acids: Toward the synthesis of an anthrax lethal factor inhibitor
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(Chemical Equation Presented) A novel and highly enantioselective Ru-catalyzed hydrogenation of N-sulfonylated-α-dehydroamino acids has been discovered and demonstrated in the synthesis of an anthrax lethal factor inhibitor (LFI). Herein, this methodology is used to prepare N-sulfonylated amino acids in up to 98% ee. This unprecedented hydrogenation uses a chiral Ru catalyst rather than Rh as typical for acylated dehydroamino acids and esters, and this work reports the first asymmetric hydrogenation of a tetrasubstituted dehydroamino acid derivative using a Ru catalyst.
- Shultz, C. Scott,Dreher, Spencer D.,Ikemoto, Norihiro,Williams, J. Michael,Grabowski, Edward J. J.,Krska, Shane W.,Sun, Yongkui,Dormer, Peter G.,DiMichele, Lisa
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p. 3405 - 3408
(2007/10/03)
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- Zinc-mediated radical reaction of glyoxylic oxime ether and hydrazone in aqueous media: Asymmetric synthesis of α-amino acids
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Alkyl radical addition to glyoxylic oxime ether and hydrazone in aqueous media was studied using zinc dust as a radical initiator. The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated prod
- Ueda, Masafumi,Miyabe, Hideto,Nishimura, Azusa,Sugino, Hisako,Naito, Takeaki
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p. 2857 - 2859
(2007/10/03)
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- Highly selective deprotection of tert-butyl esters using ytterbium triflate as a catalyst under mild conditions
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Ytterbium triflate catalyses the deprotection of tert-butyl esters selectively in the presence of other esters under mild conditions in almost quantitative yields. The reactions are carried out in nitromethane (45°-50°C) using 5 mole percent of the catalyst.
- Sridhar, P. Ramu,Sinha, Surajit,Chandrasekaran
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p. 157 - 160
(2007/10/03)
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- Asymmetric synthesis ofa-amino acids: Indium-mediated reactions of glyoxylic oxime ether in aqueous media
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The indium-mediated allylation and alkylation reactions of the Oppolzer camphorsultam derivative of glyoxylic oxime ether proceeded with excellent diastereoselectivity in aqueous media, providing a variety of enantiomerically purea-amino acids.
- Miyabe, Hideto,Nishimura, Azusa,Ueda, Masafumi,Naito, Takeaki
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p. 1454 - 1455
(2007/10/03)
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- A novel concept in combinatorial chemistry in solution with the advantages of solid-phase synthesis: Formation of N-betaines by multicomponent domino reactions
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Advantages of solid-phase and liquid-phase synthesis are combined in a new concept of combinatorial chemistry: a domino sequence comprising Knoevenagel and hetero-Diels-Alder reactions, with subsequent hydrogenation starting from protected aminoaldehydes, 1.3-dicarbonyl compounds, and enol ethers leads to N-heterocycles of high diversity with a betaine structure, which are isolated in highly pure form by precipitation with diethyl ether (see scheme), Cbz = benzylocycarbonyl, Bn = benzyl.
- Tietze, Lutz F.
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p. 903 - 905
(2007/10/03)
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- Total syntheses and biological investigations of tamandarins A and B and tamandarin A analog
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Tamandarins A (1) and B (2), two natural products similar in structure to didemnin B (3), were recently isolated from a Brazilian marine ascidian of the family Didemnidae. The cytotoxicity of 1 was reported to be somewhat more potent in vitro than that of 3 against various human cancer cell lines. The present account describes the first total syntheses of 1 and 2, and the syntheses of tamandarin A side chain analogues. The cytotoxicity data for these compounds show that the side chain modifications exhibit a parallel effect for both didemnins and tamandarins. This observation supports tamandarins' role as didemnins' mimic.
- Liang,Richard,Portonovo,Joullie
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p. 4469 - 4474
(2007/10/03)
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- Asymmetric synthesis of α-amino acids based on carbon radical addition to glyoxylic oxime ether
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The first asymmetric synthesis of α-amino acids based on diastereoselective carbon radical addition to glyoxylic imine derivatives is reported. The addition of an isopropyl radical, generated from i-PrI, Bu3SnH, and Et3B in CH2Cl2 at 25 °C, to achiral glyoxylic oxime ether 1 proceeded regioselectively at the imino carbon atom of the oxime ether group to give an excellent yield of the C-isopropylated product 2. The competitive reaction using glyoxylic oxime ether 1 and aldoxime ether 4 showed that the reactivity of the glyoxylic oxime ether toward nucleophilic carbon radicals was enhanced by the presence of a neighboring electron-withdrawing substituent. Thus, the alkyl radical addition to glyoxylic oxime ether 1 proceeded smoothly even at -78 °C, in contrast to the unactivated aldoxime ether 4. A high degree of stereocontrol in the carbon radical addition to the glyoxylic oxime ether was achieved by using Oppolzer's camphorsultam as a chiral auxiliary. The stannyl radical-mediated reaction of the camphorsultam derivative 6 with an isopropyl radical at -78 °C afforded a 96:4 diastereomeric mixture, 7a, of the C-isopropylated product. The reductive removal of the benzyloxy group of the major diastereomer (R)-7a, by treatment with Mo(CO)6 and the subsequent removal of the sultam auxiliary by standard hydrolysis, afforded the enantiomerically pure D-valine (R)-12 without any loss of stereochemical purity. To evaluate the new methodology, a variety of alkyl radicals were employed in the addition reaction which gave the alkylated products 7 with excellent diastereoselectivity, allowing access to a wide range of enantiomerically pure natural and unnatural α-amino acids. Even in the absence of Bu3SnH, treatment of 6 with alkyl iodide and Et3B at 20 °C gave the C-alkylated products 7 with moderate diastereoselectivities. The use of Et2Zn as a radical initiator, instead of Et3B, was also effective for the radical reaction. The enantioselective isopropyl radical addition to 1 using (R)-(+)-2,2'-isopropylidenebis(4-phenyl-2-oxazoline) and MgBr2 gave excellent chemical yield of the valine derivative 2 in 52% ee.
- Miyabe, Hideto,Ushiro, Chikage,Ueda, Masafumi,Yamakawa, Kumiko,Naito, Takeaki
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p. 176 - 185
(2007/10/03)
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- Total synthesis of (-)-tamandarin B
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The synthesis of tamandarin B is described. Key steps in the synthesis of the macrocycle component include a diastereoselective ketone reduction, linear precursor formation via an activated pentafluorophenyl ester, and HATU-promoted cyclization. Side-chain coupling was achieved in excellent yield with the newly developed coupling reagent DEPBT. (C) 2000 Published by Elsevier Science Ltd.
- Joullie,Portonovo,Liang,Richard
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p. 9373 - 9376
(2007/10/03)
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- New facile alkoxycarbonylating agent, alkyl pyrazole-1-carboxylates. The preparation and the utilities
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Alkyl pyrazole-1-carboxylates (2), which were readily prepared from alkyl chloroformate or carbazate in good yields, were provided as the new facile alkoxycarbonylating agents toward the Grignard reagents for the synthesis of one carbon higher carboxylic esters. Also amines were alkoxycarbonylated by 2 to produce the corresponding urethanes even in an aqueous medium. Benzyl 3,5-dimethylpyrazole-1-carboxylate (2d) could be utilized for the Cbz-protection of amino acids and esters in good yield without any racemization.
- Kashima, Choji,Tsuruoka, Shiro,Mizuhara, Saori
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p. 14679 - 14688
(2007/10/03)
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- Synthesis of Racemic α-Amino Carboxamides via Lewis Acid-Mediated Reactions of α-Methoxyglycinamide Derivatives with Allylsilanes: Enzymatic Resolution to Optically Active α-Amino Acids
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A short and expedient synthetic route to optically active, saturated and γ,δ-unsaturated α-amino acids is reported.The key step is a BF3*Et2O-mediated reaction of allylsilanes with N-(alkoxycarbonyl)-α-methoxyglycinamides 11-15, leading to the corresponding γ,δ-unsaturated α-aminocarboxamides.The genuine SN1-character of this process with iminium ion 6 as intermediate is proven in the case of the glycine ester 10.Thus, reaction of enzymatically resolved 10 with ?-nucleophiles leads to racemic products.The most useful iminium precursors are the N-methoxyamides 12-14 providing good yields of coupling products.The most convenient N-protective group is the allyloxycarbonyl group.Deprotection proceeds via a Pd(O)-catalyzed transprotection to the corresponding BOC-protected analogues.Four examples of the enzymatic resolution of α-amino carboxamides, by using an L-specific aminopeptidase from Pseudomonas putida, are described in detail.Most notably, secondary N-methoxyamides are good substrates for the enzyme to provide the desired α-amino acids in high optical purity.
- Roos, Eric C.,Mooiweer, Hendrik H.,Hiemstra, Henk,Speckamp, W. Nico,Kaptein, Bernard,et al.
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p. 6769 - 6778
(2007/10/02)
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- Synthesis and functional evaluation of a peptide derivative of 1-β-D- arabinofuranosylcytosine
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We have synthesized a peptidyl prodrug derivative of 1-β-D- arabinofuranosylcytosine (1) designed to be a selective substrate of plasmin. D-Val-Leu-Lys-ara-C (2) was obtained by coupling the protected peptide Cbz-D- Val-Leu-(N6-Cbz)Lys-OH and a
- Balajthy,Aradi,Kiss,Elodi
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p. 3344 - 3349
(2007/10/02)
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- Optical Resolution of Unusual Amino-Acids by Lipase-catalysed Hydrolysis
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The 2-chloroethyl esters of the N-benzyloxycarbonyl (Z) derivatives of several unusual amino-acids are converted by Aspergillus niger lipase into enantiomerically enriched Z-amino-acids with fairly high optical purities, the L-enantiomers being preferentially hydrolysed.
- Miyazawa, Toshifumi,Takitani, Tadanori,Ueji, Shinichi,Yamada, Takashi,Kuwata, Shigeru
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p. 1214 - 1216
(2007/10/02)
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- Amino alcohols as C-Terminal Protecting Groups in Peptide Synthesis
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The synthesis of peptides using amino alcohols as C-terminal protecting groups is described.C-Terminal protection of amino acid could be accomplished by reduction of the terminal carboxyl group to a hydroxymethyl group, and regeneration of the carboxyl group could be achieved by Jones' oxidation.This method was applied to the formation of di- and tripeptides.
- Kashima, Choji,Harada, Kazuo,Fujioka, Yoko,Maruyama, Tatsuya,Omote, Yoshimori
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p. 535 - 540
(2007/10/02)
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- Direct Optical Resolution of Carboxylic Acids by Chyral HPLC on Tris(3,5-dimethylphenylcarbamate)s of Cellulose and Amylose
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A variety of racemic carboxylic acids have been for the first time directly resolved by normal-phase, high-performance liquid chromatography using a hexane-2-propanol eluting system containing a small amount (ca. 1percent) of a strong carboxylic acid, like formic acid, trichloroacetic acid, and trifluoroacetic acid.
- Okamoto, Yoshio,Aburatani, Ryo,Kaida, Yuriko,Hatada, Koichi
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p. 1125 - 1128
(2007/10/02)
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- PAPAIN-ASSISTED RESOLUTION OF NATURAL AND XENOBIOTIC α-AMINO ACIDS
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A new and convenient method for the preparation of pure enantiomers of α-amino acids is described.Industrial papain, catalyzes the synthesis of L-Z-amino acid ethyl esters in ethanolic medium, with good yields.These esters are obtained from DL-Z-amino acids with 100percent optical purity.Unreactive D-Z-amino acids are readily isolated from reaction medium.Physical constants of natural and xenobiotic L-Z-amino acid esters and D-Z-amino acids are described.
- Moriniere, J. L.,Danree, B.,Lemoine, J.,Guy, A.
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p. 441 - 444
(2007/10/02)
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- Composition containing a penem or carbapenem antibiotic and the use of the same
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Administration of an N-acylated amino acid in association with a penem or carbapenem antibiotic relieves or eliminates the renal problems associated with administration of the antibiotic alone. The amino acid derivative and antibiotic may be formulated together as a composition or administered separately, either simultaneously or sequentially.
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- UTILISATION DES HYDROLASES EN CHIMIE ORGANIQUE: SYNTHESE DE LIAISONS ESTER ET AMIDE CATALYSEE PAR LA PAPAINE INDUSTRIELLE
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The use of hydrolases in organic chemistry: synthesis of amide and ester bonds catalyzed by industrial papain.Industrial papain, which is readily available, catalyzed the synthesis of L-Z-alanine ethyl ester (L-ZAEt) in organic medium, under different conditions, with good yields.L-ZAEt was obtained from DL-Z-alanine with 100 percent optical purity.We studied the effects of pH, the solvent/substrate and papain/substrate ratios and the type of organic solvent added, on the L-ZAEt yield.Unreactive D-ZA was also easily isolated from the aqueous phase with good optical purity.This attractive method has been applied to other N-Z-amino acid esters with the same succes.This procedure has been developed for the preparation of peptides using carboxylic or phosphonic substrates.These peptides have anti-bacterial activity. enzymatic catalysis / papain / chymopapain / stereospecific esterification of carboxylic amino acids / dipeptides / phosphonopeptides / anti-bacterial activity
- Moriniere, Jean-Luc,Danree, Bernard,Guy, Alain
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p. 347 - 358
(2007/10/02)
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- DIISOPROPYLETHYLAMINE ELIMINATES DIPEPTIDE FORMATION DURING THE ACYLATION OF AMINO ACIDS USING BENZOYL CHLORIDE AND SOME ALKYL CHLOROFORMATES
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Acylation of amino acids using benzoyl chloride in aqueous alkali leads to benzoylamino acids containing one percent of benzoyldipeptide.Use of diisopropylethylamine instead of sodium hydroxide as base eliminates the side reaction responsible for the contaminant.Ethoxycarbonylamino acids are advantageously prepared in the same manner using ethyl chloroformate or diethyl dicarbonate.The latter gives rise to some N-substituted dipeptide when used in aqueous alkali.The method is unsatisfactory for the benzyloxycarbonylation of amino acids.Use of 9-fluorenylmethyl chloroformate and diisopropylethylamine gives the pure derivative of leucine in moderate yield.
- Chen, Francis M. F.,Benoiton, N. Leo
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p. 1224 - 1227
(2007/10/02)
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- Composition containing a penem or carbapenem antibiotic
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Administration of an N-acylated amino acid in association with a penem or carbapenem antibiotic relieves or eliminates the renal problems associated with administration of the antibiotic alone. The amino acid derivative and antibiotic may be formulated together as a composition or administered separately, either simultaneously or sequentially. The composition may be prepared by simple mixing.
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