- Ferrocene-modified amino acids: synthesis and in vivo bioeffects on hippocampus
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A method for the ferrocene modification of amino acids of natural and synthetic origin has been developed. In the in vivo studies, the hippocampal electrical activity under the action of ferrocenyl(phenylpyrazolyl)glycine (1) was assessed. A meaningful rise (up to 25% compared to the control) in the response amplitudes of the focal potentials of the hippocampal region СА1 after intraperitoneal administration of compound 1 at the dose of 2.0 mg kg–1 was established.
- Rodionov,Snegur,Simenel,Dobryakova, Yu. V.,Markevich
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p. 136 - 142
(2017/07/05)
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- Regiodivergent Enantioselective γ-Additions of Oxazolones to 2,3-Butadienoates Catalyzed by Phosphines: Synthesis of α,α-Disubstituted α-Amino Acids and N,O-Acetal Derivatives
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Phosphine-catalyzed regiodivergent enantioselective C-2- and C-4-selective γ-additions of oxazolones to 2,3-butadienoates have been developed. The C-4-selective γ-addition of oxazolones occurred in a highly enantioselective manner when 2-aryl-4-alkyloxazol-5-(4H)-ones were employed as pronucleophiles. With the employment of 2-alkyl-4-aryloxazol-5-(4H)-ones as the donor, C-2-selective γ-addition of oxazolones took place in a highly enantioselective manner. The C-4-selective adducts provided rapid access to optically enriched α,α-disubstituted α-amino acid derivatives, and the C-2-selective products led to facile synthesis of chiral N,O-acetals and γ-lactols. Theoretical studies via DFT calculations suggested that the origin of the observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic oxazolide and the electrophilic phosphonium intermediate.
- Wang, Tianli,Yu, Zhaoyuan,Hoon, Ding Long,Phee, Claire Yan,Lan, Yu,Lu, Yixin
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supporting information
p. 265 - 271
(2016/01/25)
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- Selective oxidation of amines to aldehydes or imines using laccase-mediated bio-oxidation
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An efficient and practical chemo-enzymatic aerobic oxidation in water of benzylamines to obtain aldehydes or imines is described. Laccase from Trametes versicolor was chosen as biocatalyst, and TEMPO (radical 2,2,6,6-tetramethylpiperidine 1-oxyl) as mediator. A study on the pH dependence of the aqueous medium allowed us to realise a fine tuning on product selectivity. Under our optimized reaction conditions, the bio-oxidation of a series of primary, secondary and cyclic amines has been achieved.
- Galletti, Paola,Funiciello, Federica,Soldati, Roberto,Giacomini, Daria
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p. 1840 - 1848
(2015/06/02)
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- C-5′-substituted cinchona alkaloid derivatives catalyse the first highly enantioselective dynamic kinetic resolutions of azlactones by thiolysis
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The highly enantioselective dynamic kinetic resolution (DKR) of azlactones by thiolysis has been achieved for the first time. Although both the parent alkaloid quinine and known C-5′-urea derivatives fail to promote the reaction effectively, a new class of C-5′-hydroxylated catalysts proved capable of catalysing the DKR of a range of azlactones derived from both unbranched- and, previously challenging, branched-chain amino acids in 84-92 % ee, including an example of the synthesis of an enantioenriched N-protected thioester derived from an extraterrestrial amino acid isolated from the Murchison meteorite. The highly enantioselective dynamic kinetic resolution (DKR) of azlactones by thiolysis has been achieved for the first time. Although both the parent alkaloid quinine and known C-5′-urea derivatives fail to promote the reaction effectively, a new class of C-5′-hydroxylated catalysts proved capable of catalysing the DKR of a range of azlactones in 84-92 % ee. Copyright
- Palacio, Carole,Connon, Stephen J.
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supporting information
p. 5398 - 5413
(2013/09/02)
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- Highly tunable arylated cinchona alkaloids as bifunctional catalysts
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We report the design and evaluation of a library of chiral bifunctional organocatalysts in which the distance between the catalytically active units can be systematically varied.
- Quigley, Cormac,Rodriguez-Docampo, Zaida,Connon, Stephen J.
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supporting information; scheme or table
p. 1443 - 1445
(2012/03/11)
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- Antimicrobial toxicity studies of ionic liquids leading to a 'hit' MRSA selective antibacterial imidazolium salt
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Imidazolium salts can be classed as surfactants, detergents, ionic liquids, reagents, catalysts or solvents. A study of the toxicity and ecotoxicity of these salts yields valuable information for their use as pharmaceuticals as well as impact on the environment. Our approach to screen a series of chiral imidazolium salts for toxicity to bacteria and fungi, including clinical pathogen strains, has led to the identification of a 'hit' MRSA selective antimicrobial compound. Preliminary structure-activity-relationship (SAR) information (required position of l-phenylalanine and l-valine group) is also elucidated within this first generation of compounds. Conversely, most of the imidazolium salts were nontoxic (IC95 > 2 mM) to the 12 fungi strains and 8 bacteria strains screened, and we propose that they are suitable candidates for 'green chemistry' applications. Ecotoxicity studies (Biodegradation ISO 14593 'CO2 Headspace Test') of two bromide ionic liquids containing l-phenylalanine residues indicate that these ionic liquids passed the test (>60% in 28 days) and classed as readily biodegradable.
- Coleman, Deborah,Spulak, Marcel,Garcia, M. Teresa,Gathergood, Nicholas
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body text
p. 1350 - 1356
(2012/06/16)
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- Use of diphenyliodonium bromide in the synthesis of some N-phenyl-amino acids
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The N-phenyl methyl esters 4 of glycine, alanine, valine, leucine, isoleucine, phenylalanine, methionine, proline, serine, threonine, tyrosine, aspartic acid, and glutamic acid have been synthesized in good to excellent yields using diphenyliodonium bromide, AgNO3, and a catalytic amount of CuBr starting from the relevant amino acid ester. The chiral integrity of the amino acids 5 was maintained during these reactions, which were confirmed by the synthesis of dipeptide for each N-phenyl amino acid. The structures of the new compounds were confirmed by the analysis of their IR, 1H, and 13C NMR spectra in addition to CHN microanalysis or high-resolution mass spectrometry for the new N-phenyl amino acids 5 and the esters 4.
- McKerrow, Jason D.,Al-Rawi, Jasim M. A.,Brooks, Peter
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experimental part
p. 1161 - 1179
(2010/04/28)
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- Design and synthesis of N-methylmaleimide indolocarbazole bearing modified 2-acetamino acid moieties as Topoisomerase I inhibitors
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A novel series of N-methylmaleimide indolocarbazole derivatives bearing modified 2-acetamino acid moieties are first reported. The cytotoxic effects of these compounds were tested in five human tumor cell lines. The potent compounds 9a, 9b, 9d, and 9e have been further evaluated for their effect on Topoisomerase I (TOPO I) and cancer cell cycle. It is concluded that the indolocarbazoles with alkyl piperazine or morpholine substituent groups instead of esters or glycosyl residues would have better activities against tumors.
- Li, Zhiyu,Zhai, Fuming,Zhao, Li,Guo, Qinglong,You, Qidong
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scheme or table
p. 406 - 409
(2011/02/26)
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- Probing the efficiency of N-heterocyclic carbene promoted O- to C-carboxyl transfer of oxazolyl carbonates
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(Chemical Equation Presented) Screening of a range of azolium salts, bases and solvents for reactivity indicates that triazolinylidenes, generated in situ with KHMDS in THF, promote the Steglich rearrangement of oxazolyl carbonates with high catalytic efficiency (typical reaction time 5 min at 1.5 mol % NHC). This protocol shows wide substrate applicability, even allowing the efficient generation of vicinal quaternary centers. An improved experimental procedure is also described that allows a simplified one-pot reaction protocol to be employed with similarly high catalytic efficiency.
- Thomson, Jennifer E.,Campbell, Craig D.,Concellon, Carmen,Duguet, Nicolas,Rix, Kathryn,Slawin, Alexandra M. Z.,Smith, Andrew D.
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p. 2784 - 2791
(2008/09/20)
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- Simple and effective preparation of amino sulfonylureas from amino acids: application to the synthesis of amino sulfonylurea-containing peptidomimetics
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Several amino sulfonylureas have been synthesized, starting from amino acids. The synthetic procedure is simple affording high yields of products under mild conditions. Furthermore, it is shown that these compounds can be incorporated into a peptide sequence.
- ?ink, Roman,Zega, Anamarija
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p. 3943 - 3945
(2008/09/21)
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- Organosilicon synthesis of isocyanates: IV. Synthesis of isocyanates from aliphatic and alkylaromatic amino acid esters
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Treatment of an alcoholic suspension of amino acids with trimethylchlorosilane yielded phenylglycine, valine, β-phenylalanine, and homovaline ester hydrochlorides. Their saccharin-catalyzed silylation with hexamethyldisilazane proceeds quantitatively and involves only one proton of the amino group. The best conversion of the amino acid esters to the corresponding isocyanates was achieved by phosgene treatment of their monosilyl urethanes, rather than of the silylated amino esters. Monosilyl urethanes are formed quantitatively by treatment of the amino acid ester hydrochlorides with the hexamethyldisilazane-CO2 system. The 1H NMR spectra show that monosilyl urethanes derived from α-and β-amino acid esters are characterized by intramolecular interaction of the silicon atom and the oxygen atom of the carboxy group. Nauka/Interperiodica 2007.
- Lebedev,Lebedeva,Sheludyakov,Shatunov,Ovcharuk
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p. 581 - 585
(2008/02/11)
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- Meteoritic Cα-methylated α-amino acids and the homochirality of life: Searching for a link
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Catch a falling star: Peptides from chiral, Cα-methylated α-amino acids (see scheme) found in L enantiomeric excess in meteorites show diastereoselectivity when reacting with racemic proteinogenic amino acids. Accordingly, the prebiotic soup of proteinogenic amino acids may have evolved into a chirally unbalanced system, eventually seeding the homochirality of life.
- Crisma, Marco,Moretto, Alessandro,Formaggio, Fernando,Kaptein, Bernard,Broxterman, Quirinus B.,Toniolo, Claudio
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p. 6695 - 6699
(2007/10/03)
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- New 2-(2'-phenyl-9'-benzyl-8'-azapurin-6'-ylamino)-carboxylic acid methylesters as ligands for A1 adenosine receptors.
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Synthesis of a series of new 2-phenyl-9-benzyl-8-azaadenines bearing on N6 an alkyl or aralkyl chain having a carbonyloxymethyl group on the carbon bound to N6 were reported. The ester group could assure to the molecule a better water-solubility than the 8-azaadenines 2, 6 and 9 substituted with lipophilic groups synthesised in the past. Compounds synthesised demonstrated only little capability of binding A1 adenosine receptors.
- Biagi,Giorgi,Pacchini,Livi,Scartoni
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p. 929 - 931
(2007/10/03)
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- Metal Complexes with Biologically Important Ligands, XLV. - Palladium(II) Complexes of Dehydro-α-amino and 2-Imino Acid Esters as Ligands
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The preparation and spectroscopic data of the complexes trans-Cl2Pd(H2NC(CO2R)=C)2 (1) and trans-Cl2Pd(HN=C(CO2R)-CH)2 (6) and of (+)BF4(-) (2) are reported.The reactions of dehydroamino acid esters R(ROC)-C=C(CO2R)NH2 with Na2PdCl4 give 1-imino-3-ketonato chelate complexes cis- (3), of which one representative (3b) has been characterized by X-ray structure analysis.For comparison the structure of the dehydroamino acid derivative OC(Me)C(CO2Et)=C(CO2Et)NH2 (4) has also been determined.Palladium(II) binds the anion of dehydroarmentomycin via the N,O atoms (8).This coordination is also found with (η5-C5H5)(OC)2Mo and allylglycine (9).
- Wanjek, Herbert,Nagel, Ulrich,Beck, Wolfgang
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p. 1021 - 1026
(2007/10/02)
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- REGIOSELECTIVE CHLORINATION OF VALINE DERIVATIVES
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Reaction of N-benzoylvaline methyl ester (5a) with sulphuryl chloride gave the β-chlorovaline derivative (6a) and lesser amounts of diastereoisomers of the γ-chlorovaline derivative (7a).A similar mixture of products was obtained throuch photolysis of the N-chloroamide (13).The reactions of the valine derivatives (5a) and (13) involve regioselective intermolecular transfer of the β-valinyl hydrogen.There is no evidence for reaction at the α-position.The β-chloroalanine derivative (23) was produced through reaction of N-benzoylalanine methyl ester (17a) with sulphuryl chloride and by photolysis of the N-chloroamide (22).Chlorination of the azetidinone (16a) gave (16b) in modest yield.These reactions establish the chemical validity of a regiospecific hydrogen-atom abstraction proposed in penicillin biosynthesis.
- Bowman, Nigel J.,Hay, Michael P.,Love, Stephen G.,Easton, Christopher J.
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p. 259 - 264
(2007/10/02)
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- REGIOSELECTIVE FORMATION OF AMIDOCARBOXY-SUBSTITUTED FREE RADICALS
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Factors affecting the production of amidocarboxy-substituted free radicals have been investigated by examining reactions of derivatives of valine and sarcosine.Variations in the regioselectivity of reactions of these compounds are exemplified by the reactions of N-benzoylvaline methyl ester (4a) and N-benzoylsarcosine methyl ester (12a) with sulphuryl chloride and N-bromosuccinimide.Whereas the reaction of (4a) with sulphuryl chloride involves hydrogen-atom transfer from the β-position of (4a) with subsequent chlorine incorporation to give (4g), in direct contrast the reaction with N-bromosuccinimide proceeds via hydrogen-atom abstraction from the α-position of (4a) and yields the dibromide (4d).N-benzoylsarcosine methyl ester (12a), reacts with N-bromosuccinimide to give the α-bromosarcosine derivative (12b), whereas with sulphuryl chloride the product is the N-chloromethylglycine derivative (12c).These studies indicate that amidocarboxy-substituted radicals such as (3a) and (13) are considerably more stable than the tertiary alkyl radical (1a) and the amidosubstituted radical (14), respectively, but hydrogen-atom transfer reactions may afford the less stable products if electrophilic radicals are involved in the hydrogen-atom abstraction and if there is little development of radical character in the reaction transition state.
- Easton, Christopher J.,Hay, Michael P.,Love, Stephen G.
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p. 265 - 268
(2007/10/02)
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