- Concentration- and Structure-Dependent Effects of Amides on Protease Activity in Organic Solvents
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The catalytic activity of α-chymotrypsin (CT) in the transesterification of N-acetyl-L-tyrosine methyl ester to its ethyl ester in aqueous-organic media was markedly enhanced by replacing a part of water with foramide.The activity of CT was strongly dependent on the formamide/water ratio, and excess formamide retarded the activity.Addition of formamide to reaction mixtures at constant water contents exhibited similar activation-deactivation profiles for CT.A kinetic study revealed that the rate acceleration is due to an increase in kcat rather than a change in Km.At a given concentration of amides (0.5 M, M = mol dm-3), propionamide and DMF were much less effective than formamide for activation of CT.The results suggest that foramide interacts with CT in a different way from water.
- Yamamoto, Yasuhito,Kise, Hideo
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- Catalytic specificity exhibited by p-sulfonatocalix[n]arenes in the methanolysis of N-acetyl-L-amino acids
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Specific acid catalysis of p-sulfonatocalix[n]arenes (n = 4, Calix-S4; n = 6, Calix-S6; n = 8, Calix-S8) was observed in the alcoholysis of N-acetyl-L-amino acids in methanol. The methanolysis rates of basic amino acid substrates (His, Lys, and Arg) were
- Goto, Koichi,Yano, Yoshihiro,Okada, Eiji,Liu, Chin-Wen,Yamamoto, Kiyoto,Ueoka, Ryuichi
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- Effects of metal salts on the structure and activity of α-chymotrypsin in ethanol/water
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The catalytic activity and circular dichroic (CD) spectra of α- chymotrypsin (CT) were measured in ethanol/water (95/5, v/v) solution containing small amounts of metal salts. Although the catalytic activity of CT increased upon the addition of all the metal salts used, the magnitude of activity increase was different for different metal salts. Especially, calcium acetate accelerated the transesterification of amino acid up to 6 fold at 100 μM. The secondary and tertiary structures of CT were also changed by metal salts, as studied by CD measurements. The effects of metal salts on the stability of CT in ethanol/water were also studied, and it was found that the residual activity of CT after 7 days in ethanol/water in the presence of Ca(OCOCH3)2 was about 20% of the initial activity. The change in activity was closely correlated with the change in the mean residue ellipticity of CT at 208 or 230 nm.
- Sasaki, Toshiya,Kise, Hideo
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- Solid-Supported tert-Alkoxycarbonylation Reagents for Anchoring of Amines during Solid Phase Organic Synthesis
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The preparation and characterization of a homologous series of solid phase synthesis resins for anchoring amines via a Boc-like linker are described. The scope and limitations of these resins are explored with respect to procedures for attachment and clea
- Hernandez, Andres S.,Hodges, John C.
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- Increase of catalytic activity of alpha-chymotrypsin by metal salts for transesterification of an amino acid ester in ethanol.
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alpha-Chymotrypsin-catalyzed transesterification of N-acetyl-L-tyrosine methyl ester in ethanol was markedly accelerated by addition of small amounts of divalent metal salts. The reaction rate dependent not only on the nature of metal ions but also on the nature of anionic counter ions. Calcium acetate was the most effective among the metal salts used. The reaction followed Michaelis-Menten kinetics, and it was found that the reaction increase is due to the increase in kcat.
- Sasaki,Kise
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- Discovery of Modified Amidate (ProTide) Prodrugs of Tenofovir with Enhanced Antiviral Properties
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This study describes the discovery of novel prodrugs bearing tyrosine derivatives instead of the phenol moiety present in FDA-approved tenofovir alafenamide fumarate (TAF). The synthesis was optimized to afford diastereomeric mixtures of novel prodrugs in
- Kal?ic, Filip,Zgarbová, Michala,Hodek, Jan,Chalupsky, Karel,Dra?ínsky, Martin,Dvo?áková, Alexandra,Strmeň, Timotej,?ebestík, Jaroslav,Baszczyňski, Ond?ej,Weber, Jan,Mertlíková-Kaiserová, Helena,Janeba, Zlatko
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p. 16425 - 16449
(2021/11/16)
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- A Metal-Free Direct Arene C?H Amination
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The synthesis of aryl amines via the formation of a C?N bond is an essential tool for the preparation of functional materials, active pharmaceutical ingredients and bioactive products. Usually, this chemical connection is only possible by transition metal-catalyzed reactions, photochemistry or electrochemistry. Here, we report a metal-free arene C?H amination using hydroxylamine derivatives under benign conditions. A charge transfer interaction between the aminating reagents TsONHR and the arene substrates enables the chemoselective amination of the arene, even in the presence of various functional groups. Oxygen was crucial for an effective conversion and its accelerating role for the electron transfer step was proven experimentally. In addition, this was rationalized by a theoretical study which indicated the involvement of a dioxygen-bridged complex with a “Sandwich-like” arrangement of the aromatic starting materials and the aminating agents at the dioxygen molecule. (Figure presented.).
- Wang, Tao,Hoffmann, Marvin,Dreuw, Andreas,Hasagi?, Edina,Hu, Chao,Stein, Philipp M.,Witzel, Sina,Shi, Hongwei,Yang, Yangyang,Rudolph, Matthias,Stuck, Fabian,Rominger, Frank,Kerscher, Marion,Comba, Peter,Hashmi, A. Stephen K.
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supporting information
p. 2783 - 2795
(2021/04/05)
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- Tyrosine-Specific Modification via a Dearomatization-Rearomatization Strategy: Access to Azobenzene Functionalized Peptides
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Azobenzene functionalized peptides are of great importance in photoresponsive biosystems and photopharmacology. Herein, we report an efficient approach to prepare azobenzene functionalized peptides through late-stage modification of tyrosine-containing peptides using a dearomatization-rearomatization strategy. This approach shows good chemoselectivity and site selectivity as well as sensitive group tolerance to various peptides. This method enriches the postsynthetic modification toolbox of peptides and has great potential to be applied in medicinal chemistry and chemical biology.
- Cheng, Yulian,Cheng, Zhehong,Fang, Lijing,Li, Hongchang,Su, Wu,Wang, Pengxin,Wang, Rui,Wu, Chunlei,Zhou, Yimin
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supporting information
p. 4137 - 4141
(2021/06/27)
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- Preparation method of rosastat key intermediate
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The invention provides a preparation method of a rosastat key intermediate. The intermediate I is 4-hydroxy-1-methyl-7-phenoxy isoquinoline-3-carboxylic ester. The preparation method comprises the following steps: with tyrosine as an initial raw material, sequentially carrying out esterification, acylation, etherification, cyclization, aromatization and oxidation rearrangement reaction to preparethe rosastat key intermediate. The preparation method has the advantages of cheap and easily available raw materials, environmental protection, avoiding of use of phosphorus oxychloride, polyphosphoric acid and other environmentally unfriendly reagents in the cyclization reaction, simple process, simple operation and mild reaction conditions; and the method has the advantages of less three wastesand higher product yield and purity, and is suitable for industrial production.
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Paragraph 0053-0056
(2020/09/09)
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- REAGENTS AND PROCESS FOR DIRECT C-H FUNCTIONALIZATION
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Thianthrene derivative of the Formula (I): wherein R1 to R8 may be the same or different and are selected from hydrogen, Cl, F, a partially or fully fluorinated C1 to C6 alkyl group, and wherein n is 0 or 1, with the proviso that at least one of R1 to R8 is not hydrogen and process for C-H functionalization of aromatic compounds using this compound.
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Page/Page column 107-108
(2020/06/01)
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- Site-Selective C?H Oxygenation via Aryl Sulfonium Salts
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Herein, we report a two-step process forming arene C?O bonds in excellent site-selectivity at a late-stage. The C?O bond formation is achieved by selective introduction of a thianthrenium group, which is then converted into C?O bonds using photoredox chemistry. Electron-rich, -poor and -neutral arenes as well as complex drug-like small molecules are successfully transformed into both phenols and various ethers. The sequence differs conceptually from all previous arene oxygenation reactions in that oxygen functionality can be incorporated into complex small molecules at a late stage site-selectively, which has not been shown via aryl halides.
- Sang, Ruocheng,Korkis, Stamatis E.,Su, Wanqi,Ye, Fei,Engl, Pascal S.,Berger, Florian,Ritter, Tobias
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supporting information
p. 16161 - 16166
(2019/11/03)
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- Visible-Light-Induced [4+2] Annulation of Thiophenes and Alkynes to Construct Benzene Rings
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The [4+2] annulation represents an elegant and versatile synthetic protocol for the construction of benzene rings. Herein, a strategy for visible-light induced [4+2] annulation of thiophenes and alkynes, to afford benzene rings, is presented. Under simple and mild reaction conditions, the ready availability and structural diversity of thiophenes and alkynes permit the facile synthesis of several substituted aromatic rings. Valuable drugs and amino acids are also well tolerated. Moreover, DFT calculations explain the high regioselectivity of the reaction.
- Song, Chunlan,Dong, Xin,Wang, Zhongjie,Liu, Kun,Chiang, Chien-Wei,Lei, Aiwen
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supporting information
p. 12206 - 12210
(2019/07/31)
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- Selective Photoredox Trifluoromethylation of Tryptophan-Containing Peptides
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For application in drug discovery and biomedicine, it is crucial to develop new biocompatible methods to modify polypeptides. Herein, a visible-light-induced photoredox trifluoromethylation of tryptophan-containing peptides is reported. Under a mild, biocompatible, and straightforward condition, this strategy could incorporate the trifluoromethyl group into tryptophan residue with excellent chemo- and site-selectivity. The use of lower photocatalyst loading in 2 mol-% and cheap CF3SO2Na salt represents a great catalytic activity and economic CF3 source. This direct trifluoromethylation strategy allows the ready study of fluorinated peptides exploiting 19F-NMR. Additionally, the development of this protocol enables the study of biochemical systems and potentially modulates the function of biomolecules. Careful mechanistic studies (Stern-Volmer fluorescence quenching, EPR, and radical inhibition/trapping experiments) indicate that the reaction would proceed with a radical–radical cross-coupling procedure.
- Ding, Bo,Weng, Yue,Liu, Yunqing,Song, Chunlan,Yin, Le,Yuan, Jiafan,Ren, Yanrui,Lei, Aiwen,Chiang, Chien-Wei
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p. 7596 - 7605
(2019/12/15)
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- Oxidative functionalization of aliphatic and aromatic amino acid derivatives with H2O2 catalyzed by a nonheme imine based iron complex
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The oxidation of a series of N-acetyl amino acid methyl esters with H2O2 catalyzed by a very simple iminopyridine iron(ii) complex 1 easily obtainable in situ by self-assembly of 2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 was investigated. Oxidation of protected aliphatic amino acids occurs at the α-C-H bond exclusively (N-AcAlaOMe) or in competition with the side-chain functionalization (N-AcValOMe and N-AcLeuOMe). N-AcProOMe is smoothly and cleanly oxidized with high regioselectivity affording exclusively C-5 oxidation products. Remarkably, complex 1 is also able to catalyze the oxidation of the aromatic N-AcPheOMe. A marked preference for the aromatic ring hydroxylation over Cα-H and benzylic C-H oxidation was observed, leading to the clean formation of tyrosine and its phenolic isomers.
- Ticconi, Barbara,Colcerasa, Arianna,Di Stefano, Stefano,Lanzalunga, Osvaldo,Lapi, Andrea,Mazzonna, Marco,Olivo, Giorgio
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p. 19144 - 19151
(2018/05/31)
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- Radical arylation of tyrosine residues in peptides
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The radical arylation of the phenolic side chain of tyrosine in peptides was investigated. Aryl radicals were generated from aryldiazonium salts using titanium(III) chloride as stoichiometric reductant. Due to the high selectivity with which 3-aryltyrosine derivatives were formed, this reaction type represents a new strategy for the direct functionalization of peptides.
- Fehler, Stefanie K.,Pratsch, Gerald,?streicher, Christiane,Fürst, Michael C.D.,Pischetsrieder, Monika,Heinrich, Markus R.
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supporting information
p. 7888 - 7893
(2016/11/17)
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- Oxidative damage of aromatic dipeptides by the environmental oxidants NO2 and O3
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Irreversible oxidative damage at both aromatic side chains and dipeptide linkage occurs in the aromatic N- and C-protected dipeptides 7-11 upon exposure to the environmental pollutants NO2 and O3. The reaction proceeds through initial oxidation of the aromatic ring by in situ generated NO3, or by NO2, respectively, which leads to formation of nitroaromatic products. The indole ring in Phe-Trp undergoes oxidative cyclization to a pyrroloindoline. An important reaction pathway for dipeptides with less oxidisable aromatic side chains proceeds through fragmentation of the peptide bond with concomitant acyl migration. This process is likely initiated by an ionic reaction of the amide nitrogen with the NO2 dimer, N2O4. This journal is
- Gamon,White,Wille
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p. 8280 - 8287
(2015/01/08)
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- Total synthesis of (-)-renieramycin G from l-tyrosine
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(-)-Renieramycin G was synthesized in 21 steps for the longest linear sequences employing l-tyrosine methyl ester as the chiral starting material in 8.5% overall yield. Two of the four chiral centers came from l-tyrosine methyl ester, and the other two we
- Liao, Xiang Wei,Liu, Wei,Dong, Wen Fang,Guan, Bao He,Chen, Shi Zhi,Liu, Zhan Zhu
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supporting information; experimental part
p. 5709 - 5715
(2009/12/04)
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- Discovery of hydrolytic catalysts in a peptidocalixarene library by binding assay with a transition state analogue for the hydrolysis
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Hydrolytic catalysts were found in a peptidocalixarene library by binding assay with a transition state analogue for the hydrolysis. The rate of the reaction can be specifically enhanced up to 50-fold in the presence of the discovered catalyst. The Royal
- Hioki, Hideaki,Nishimoto, Ryosuke,Kawaguchi, Kota,Kubo, Miwa,Harada, Kenichi,Fukuyama, Yoshiyasu
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supporting information; experimental part
p. 7194 - 7196
(2010/03/25)
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- Methanolysis of ethyl esters of N-acetyl amino acids catalyzed by cyclosophoraoses isolated from Rhizobium meliloti
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Methanolysis of four ethyl esters, N-acetyl-l-phenylalanine ethyl ester, N-acetyl-l-tyrosine ethyl ester, N-acetyl-l-tryptophan ethyl ester, and ethyl phenylacetate was catalyzed by a mixture of microbial cyclooligosaccharides termed cyclosophoraoses isolated from Rhizobium meliloti. Cyclosophoraoses [cyclic-(1→2)-β-d-glucans, collectively 'Cys'] are a mixture of large-ring molecules consisting of various numbers of glucose residues (17-27) linked by β-(1→2)-glycosidic bonds. Cys as a catalytic carbohydrate enhanced the methanolysis about 233-fold for N-acetyl-l-tyrosine ethyl ester in comparison with a control. The effect of dry organic solvents on the methanolysis of N-acetyl-l-tyrosine ethyl ester was investigated by high-performance liquid chromatography (HPLC), and it was found that the rate enhancement correlated closely with the hydrophobicity of the solvent.
- Park, Heylin,Jung, Seunho
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p. 274 - 281
(2008/09/19)
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- FUNCTIONALIZED AMINO ACIDS AND ABSORBABLE POLYMERS THEREFROM
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The present invention relates to compounds of formula I and II, which are functionalized amino acids, and polymers formed from the same. Polymers formed from the functionalized amino acids are expected to have controllable degradation profiles, enabling them to release an active component over a desired time range. The polymers are also expected to be useful in a variety of medical applications.
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Page/Page column 38-39
(2008/06/13)
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- FUNCTIONALIZED DIPHENOLICS AND ABSORBABLE POLYMERS THEREFROM
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The present invention relates to dephenolic compounds, an example of which is shown below, which are functionalized, and polymers formed from the same. Polymers formed from the functionalized diphenolics are expected to have controllable degradation profiles, enabling them to release an active component over a desired time range. The polymers are also expected to be useful in a variety of medical applications.
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Page/Page column 24
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- Synthesis and biological activities of prenylated tyrosine derivatives, the metabolites of Pithomyces ellis
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2-[4-(2E)-3-Methylbut-2-enyloxy)phenyl]ethan-1-ol 3 and 3-[4-(2E)-3-methylbut-2-enyloxy) phenyl]-2-(acetylamino)propanoic acid 8 have been synthesized from 4-hydroxyphenylacetic acid 1, L-tyrosine 4, respectively, with an overall yield of 55% and 37%. The spectral data of synthetic 3 and 8 are in good agreement with those of natural 3 and 8, respectively. These synthetic 3 and 8 show significant brine shrimp lethality, but weak antioxidant and antibacterial activities.
- Venkateswarlu, Somepalli,Panchagnula, Gopala K.,Subbaraju, Gottumukkala V.
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p. 1063 - 1066
(2007/10/03)
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- A mild procedure for rapid and selective deprotection of aryl acetates using natural kaolinitic clay as a reusable catalyst
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A variety of aryl acetates are selectively cleaved to the corresponding phenols using natural kaolinitic clay in methanol under mild conditions (25°C).
- Bandgar,Uppalla,Sagar,Sadavarte
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p. 1163 - 1165
(2007/10/03)
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- A highly effective phosphinite ligand derived from D-mannitol for Rh- catalyzed asymmetric hydrogenation
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A novel chiral phosphinite 1,2,5,6-di-isopropylidene-3, 4- bis(diphenylphosphino)-D-mannitol was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its derivatives with product ee's ranging from 90% to 97%.
- Chen, Yixin,Li, Xingshu,Tong, Siu-Kuen,Choi, Michael C.K.,Chan, Albert S.C.
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p. 957 - 960
(2007/10/03)
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- Studies on the Synthesis of Aryl Ethers Using Arene-Manganese Chemistry
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Selective arylation of polyfunctional phenols, using chlorobenzene- and p-chlorotoluene-manganese tricarbonyl cations, is described.The intermediate arene-manganese complexes are found to undergo stereo- and regioselective reactions with Schoellkopf's chiral glycine enolate equivalent to give dienyl-Mn(CO)3 complexes.Treatment of these complexes with N-bromosuccinimide at room temperature, followed by hydrolysis of the dihydropyrazine, gives diaryl ethers in which one of the aromatic rings is an arylglycine methyl ester.
- Pearson, Anthony J.,Bruhn, Paul R.
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p. 7092 - 7097
(2007/10/02)
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- N-METHOXYDIACETAMIDE: A NEW SELECTIVE ACETYLATING AGENT
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A simple and efficient method for the direct chemoselective acetylation of primary amines in the presence of alcohols or secondary amines using a new reagent N-methoxydiacetamide is described.
- Kikugawa, Yasuo,Mitsui, Kimiyo,Sakamoto, Takeshi,Kawase, Masami,Tamiya, Hiroshi
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p. 243 - 246
(2007/10/02)
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