- The peculiar behavior of Picha in the formation of metallacrown complexes with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution
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The thermodynamic stability of the metallacrown complexes formed by picolinehydroxamic acid (Picha) with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution has been determined by potentiometry, and the speciation models were validated by ESI-MS and UV-visible spectrophotometry. Cu(ii) and Zn(ii) form 12-MC-4 species as the unique metallacrowns present in the solution. While for Cu(ii) the 12-MC-4 is slightly less stable than that obtained with alaninehydroxamic acid (Alaha), the opposite was found for Zn(ii). Moreover, with Cu(ii) unprecedented 15-MC-5 and 18-MC-6 species were identified under ESI-MS conditions. Picha with Ni(ii) forms, in contrast, a 15-MC-5 complex as a unique metallacrown species. Structural studies of the framework of the 12-MC-4 complexes by ab initio methods were also carried out. The results of our investigations allowed us to rationalize not only the different behaviour of Picha in the formation of metallacrowns with the three metal ions, but also the reasons which underpin the strategies for stabilization of these species reported in the literature using ancillary ligands such as pyridine. This journal is
- Marchi, Luciano,Marchetti, Nicola,Atzeri, Corrado,Borghesani, Valentina,Remelli, Maurizio,Tegoni, Matteo
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- Epoc group: Transformable protecting group with gold(iii)-catalyzed fluorene formation
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This study presents the novel concept of a transformable protecting group, which changes its properties through structural transformation. Based on this concept, we developed a 2-(2-ethynylphenyl)-2-(5-methylfuran-2-yl)-ethoxycarbonyl (Epoc) group. The Epoc group was transformed into an Fmoc-like structure with gold(iii)-catalyzed fluorene formation and was removable under Fmoc-like mild basic conditions post-transformation even though it was originally stable under strongly basic conditions. As an application for organic synthesis, the Epoc group provides the novel orthogonality of gold(iii)-labile protecting groups in solid-phase peptide synthesis. In addition, the high turnover number of fluorene formation in aqueous media is suggestive of the applicability of the Epoc group to biological systems. This journal is
- Yamamoto, Tomoya,Chang, Tsung-Che,Tanaka, Katsunori
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- Interactions between Terminally Substituted Amino Acids in an Aqueous and a Non-Aqueous Environment. Enthalpic Interaction Coefficients in Water and in N,N-Dimethylformamide at 25 deg C
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Enthalpies of dilution of the N-acetyl amides of glycine, L-alanine, L-valine, L-leucine, and L-phenylalanine, dissolved in N,N-dimethylformamide (DMF) as a solvent have been measured at 25 deg C.The results obtained have been analyzed to give the enthalpic interaction (or virial) coefficients of the solutes and these are compared with information previously obtained in aqueous systems.There are marked differences in the interaction properties in the two solvents and, while the additivity approache of Savage and Wood is applicable to the solutes in water it is suitable for representing the interactions in DMF.A correlation is presented between the enthalpic second virial coefficients in DMF and the propensity of side-chains to be in proximity in globular proteins.
- Kent, Hilary E.,Lilley, Terence H.,Milburn, Peter J.,Bloemendal, Michael,Somsen, Gus
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- Improvement in the one-carbon chain extension of esters with dimethylsulfoxonium methylide
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A recent report suggests that the reaction of dimethylsulfoxonium methylide with esters does not produce a chain-extended sulfur ylide as previously reported, but rather affords the corresponding carboxylate salt. We have investigated this assertion by using a combination of ab initio molecular orbital calculations, spiking studies, and isotopic labeling. The formation of carboxylate is unambiguously demonstrated to arise through hydrolysis involving adventitious water, principally derived from moisture in commercial trimethylsulfoxonium chloride. Careful vacuum drying of this reagent diminishes the competing hydrolytic pathway resulting in higher yields for the chain-extension reaction than previously reported. Copyright
- Luong, Hoa,Luss-Lusis, Eduard,Tanoury, Gerald J.,Nugent, William A.
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- Cyclodextrin-mediated deacylation of amino acid esters with marked stereoselectivity.
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With respect to the hydrolysis (deacylation) of Z-D(L)-amino acid esters (N-(benzyloxycarbonyl)-D(L)-amino acid p-nitrophenyl esters) mediated by alpha-, beta- and gamma-cyclodextrins (CyDs), a remarkably high enantioselectivity (L/D=9.0) was observed for the deacylation of Ala substrate with gamma-CyD. The kinetic results on the basis of the Michaelis-Menten principle indicate that the enantioselectivity should be mainly originated in the deacylation process of substrates following the formation of gamma-CyD-substrate (1 : 1) complexes. The computer modeling (molecular mechanics) studies on the inclusion complexes are also described.
- Goto, Koichi,Nakashima, Kentaro,Tanoue, Osamu,Nukushina, Satoshi,Toudo, Isao,Imamura, Chikara,Ihara, Yasuji,Matsumoto, Yoko,Ueoka, Ryuichi
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- The role of protecting groups in the formation of organogels through a nano-fibrillar network formed by self-assembling terminally protected tripeptides
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A series of eight synthetic self-assembling terminally blocked tripeptides have been studied for gelation. Some of them form gels in various aromatic solvents including benzene, toluene, xylene, and chlorobenzene. It has been found that the protecting groups play an important role in the formation of organogels. It has been observed that, if the C-terminal has been changed from methyl ester to ethyl ester the gelation property does not change significantly (keeping the N-terminal protecting group same), while the change of the protecting group from ethyl ester to isopropyl ester completely abolishes the gelation property. Similarly, keeping the identical C-terminal protecting group (methyl ester) the results of the gelation study indicate that the substitution of N-terminal protection Boc- (tert-butyloxycarbonyl) to Cbz- (benzyloxycarbonyl) does change the gelation property insignificantly, while the change from Boc- to pivaloyl (Piv-) or acetyl (Ac-) group completely eliminates the gelation property. Morphological studies of the dried gels of two of the peptides indicate the presence of an entangled nano-fibrillar network that might be responsible for gelation. FTIR studies of the gels demonstrate that an intermolecular hydrogen bonding network is formed during gelation. Results of X-ray powder diffraction studies for these gelator peptides in different states (dried gels, gel, and bulk solids) reflected that the structure in the wet gel is distinctly different from the dried gel and solid state structures. Single crystal X-ray diffraction studies of a non-gelator peptide, which is structurally similar to the gelator molecules reveal that the peptide forms an antiparallel β-sheet structure in crystals.
- Das, Apurba K.,Bose, Partha Pratim,Drew, Michael G.B.,Banerjee, Arindam
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- STEREOSELECTIVE HYDROLYSIS OF AMINO ACID ESTERS BY MODIFIED POLY(ETHYLENIMINE)S WITH COVALENTLY-LINKED DIPEPTIDE CONTAINING A HISTIDYL RESIDUE
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Stereoselective hydrolyses of chiral substrates were examined in poly(ethylenimine) derivatives with optically active groups.A high stereoselective effect, kL/kD = 3.6, is observed.The effect of the substrate structure influenced both the rate constant and the stereoselective ratio in the hydrolyses by poly(ethylenimine) derivatives.
- Kimura, Yoshiharu,Nango, Mamoru,Ihara, Yasuji,Kuroki, Nobuhiko
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- STEREOSELECTIVE HYDROLYSIS OF AMINO ACID ESTERS IN MODIFIED LINEAR POLY(ETHYLENIMINE) DOMAINS
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A large rate enhancement and a stereoselective preference are exhibited in the hydrolysis catalysed by N-decanoyl-L-histidine (2a) and a dipeptide containing L-histidyl residue (2b) in the domain of linear poly(ethylimine) derivatives.
- Kimura, Yoshiharu,Kanda, Shinichi,Nango, Mamoru,Ihara, Yasuji,Koga, Joichi,et al.
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- Enantioconvergent Cu-Catalyzed Radical C-N Coupling of Racemic Secondary Alkyl Halides to Access α-Chiral Primary Amines
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α-Chiral alkyl primary amines are virtually universal synthetic precursors for all other α-chiral N-containing compounds ubiquitous in biological, pharmaceutical, and material sciences. The enantioselective amination of common alkyl halides with ammonia is appealing for potential rapid access to α-chiral primary amines, but has hitherto remained rare due to the multifaceted difficulties in using ammonia and the underdeveloped C(sp3)-N coupling. Here we demonstrate sulfoximines as excellent ammonia surrogates for enantioconvergent radical C-N coupling with diverse racemic secondary alkyl halides (>60 examples) by copper catalysis under mild thermal conditions. The reaction efficiently provides highly enantioenrichedN-alkyl sulfoximines (up to 99% yield and >99% ee) featuring secondary benzyl, propargyl, α-carbonyl alkyl, and α-cyano alkyl stereocenters. In addition, we have converted the masked α-chiral primary amines thus obtained to various synthetic building blocks, ligands, and drugs possessing α-chiral N-functionalities, such as carbamate, carboxylamide, secondary and tertiary amine, and oxazoline, with commonly seen α-substitution patterns. These results shine light on the potential of enantioconvergent radical cross-coupling as a general chiral carbon-heteroatom formation strategy.
- Cheng, Jiang-Tao,Dong, Xiao-Yang,Gu, Qiang-Shuai,Li, Zhong-Liang,Liu, Juan,Liu, Xin-Yuan,Luan, Cheng,Wang, Fu-Li,Wang, Li-Lei,Yang, Ning-Yuan,Zhang, Yu-Feng
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supporting information
p. 15413 - 15419
(2021/09/30)
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- A General Stereocontrolled Synthesis of Opines through Asymmetric Pd-Catalyzed N-Allylation of Amino Acid Esters
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A stereo-divergent synthesis of natural and unnatural opines in stereochemically pure form is based on the direct palladium-catalyzed N-allylation of α-amino acid esters (up to 97 % ee or 99 : 1 d.r.) using methyl (E)-2-penten-4-yl carbonate in the presence of only 1 mol% of a catalyst, prepared in-situ from the C2-symmetric diphosphine iPr-MediPhos and [Pd(allyl)Cl]2. Selected target compounds (incl. a derivative of the drug enalapril) were efficiently obtained from the N-allylated intermediates by oxidative cleavage (ozonolysis) of the allylic C=C bond under temporary N-Boc-protection.
- Albat, Dominik,Neud?rfl, J?rg-Martin,Schmalz, Hans-Günther
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supporting information
p. 2099 - 2102
(2021/07/22)
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- SuFExable Isocyanides for Ugi Reaction: Synthesis of Sulfonyl Fluoro Peptides
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Herein, the sulfonyl fluoro isocyanides were first developed as a new type of SuFExable synthon, and they are used as building blocks in the Ugi reaction (U-4CR). The Ugi reaction was established and the substrate scope was investigated, and various sulfonyl fluoro α-amino amides and peptides could be reached in a one-step synthesis. Therefore, this protocol opens a new vision for SuFExable building blocks and click chemistry, and it also provides a distinct approach to sulfonyl fluoro peptides.
- Xu, Shuheng,Cui, Sunliang
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supporting information
p. 5197 - 5202
(2021/07/20)
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- Synthesis, characterization and docking studies of anti-HCV molecules
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The present study reports the synthesis and characterization of novel molecules inhibiting the spread of hepatitis C. The molecules were designed as to block the NS3/4A protease enzyme on HCV RNA. The molecules were synthesized using usual peptide synthesis techniques. Compounds with purity more than 95% were characterized and docking studies were also performed. All the compounds were characterized using physico-chemical techniques such as determination of melting point by DSC and NMR, mass, IR spectral studies. The docking studies were also conducted to assess the activity of molecules for inhibition of hepatitis C virus.
- Kumar, Satish,Santra,Dwivedi,Aryan
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p. 1221 - 1229
(2020/06/09)
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- A Next-Generation Air-Stable Palladium(I) Dimer Enables Olefin Migration and Selective C?C Coupling in Air
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We report a new air-stable PdI dimer, [Pd(μ-I)(PCy2tBu)]2, which triggers E-selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C?C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C?Br, C?OTf/OFs, and C?Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C?OTf.
- Kundu, Gourab,Rissanen, Kari,Schoenebeck, Franziska,Sperger, Theresa
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p. 21930 - 21934
(2020/10/02)
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- 1,3,2-Diazaphospholenes Catalyze the Conjugate Reduction of Substituted Acrylic Acids
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The potent nucleophilicity and remarkably low basicity of 1,3,2-diazaphospholenes (DAPs) is exploited in a catalytic, metal-free 1,4-reduction of free α,β-unsaturated carboxylic acids. Notably, the reduction occurs without a prior deprotonation of the carboxylic acid moiety and hence does not consume an additional hydride equivalent. This highlights the excellent nucleophilic character and low basicity of DAP-hydrides. Functional groups such as Cbz group or alkyl halides which can be problematic with classical transition-metal catalysts are well tolerated in the DAP-catalyzed process. Moreover, the transformation is characterized by a low catalyst loading, mild reaction conditions at ambient temperature as well as fast reaction times and high yields. The proof-of-principle for a catalytic enantioselective version is described.
- Reed, John H.,Cramer, Nicolai
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p. 4262 - 4266
(2020/07/13)
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- Diazaphosphinyl radical-catalyzed deoxygenation of α-carboxy ketones: A new protocol for chemo-selective C-O bond scission: Via mechanism regulation
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C-O bond cleavage is often a key process in defunctionalization of organic compounds as well as in degradation of natural polymers. However, it seldom occurs regioselectively for different types of C-O bonds under metal-free mild conditions. Here we report a facile chemo-selective cleavage of the α-C-O bonds in α-carboxy ketones by commercially available pinacolborane under the catalysis of diazaphosphinane based on a mechanism switch strategy. This new reaction features high efficiency, low cost and good group-tolerance, and is also amenable to catalytic deprotection of desyl-protected carboxylic acids and amino acids. Mechanistic studies indicated an electron-transfer-initiated radical process, underlining two crucial steps: (1) the initiator azodiisobutyronitrile switches originally hydridic reduction to kinetically more accessible electron reduction; and (2) the catalytic phosphorus species upconverts weakly reducing pinacolborane into strongly reducing diazaphosphinane. This journal is
- Cheng, Jin-Pei,Yang, Jin-Dong,Zhang, Jingjing
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p. 8476 - 8481
(2020/09/07)
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- Engineered Substrate for Cyclooxygenase-2: A Pentapeptide Isoconformational to Arachidonic Acid for Managing Inflammation
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Beyond the conventional mode of working of anti-inflammatory agents through enzyme inhibition, herein, COX-2 was provided with an alternate substrate. A proline-centered pentapeptide isoconformational to arachidonic acid, which exhibited appreciable selectivity for COX-2, overcoming acetic acid- and formalin-induced pain in rats to almost 80%, was treated as a substrate by the enzyme. Remarkably, COX-2 metabolized the pentapeptide into small fragments consisting mainly of di- and tripeptides that ensured the safe breakdown of the peptide under in vivo conditions. The kinetic parameter Kcat/Km for COX-2-mediated metabolism of the peptide (6.3 × 105 M-1 s-1) was quite similar to 9.5 × 105 M-1 s-1 for arachidonic acid. Evidenced by the molecular dynamic studies and the use of Y385F COX-2, it was observed that the breakage of the pentapeptide has probably been taken place through H-bond activation of the peptide bond by the side chains of Y385 and S530.
- Kaur, Baljit,Kaur, Manpreet,Kaur, Navjot,Garg, Saweta,Bhatti, Rajbir,Singh, Palwinder
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p. 6363 - 6376
(2019/07/08)
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- Preparation of chiral right-half models of antitumor bistetrahydroisoquinolinequinone natural products
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– The preparation of chiral right-half model compounds of bistetrahydroisoquinolinequinone natural products having a lactam carbonyl group (-)-1 or an aminonitrile group (+)-2 from (-)-14 was presented. The crucial steps of this synthesis include the N-methylation of compound (-)-12 and ring closure to generate (-)-19a without any epimerization at C-2.1
- Senbonmatsu, Yuki,Kimura, Shinya,Akiba, Megumi,Ando, Shingo,Saito, Naoki
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p. 1050 - 1067
(2019/07/31)
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- Synthesis and evaluation of chirally defined side chain variants of 7-chloro-4-aminoquinoline to overcome drug resistance in malaria chemotherapy
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A novel 4-aminoquinoline derivative [(S)-7-chloro-N-(4-methyl-1-(4-methyl-piperazin-1-yl)pentan-2-yl)-quinolin-4-amine triphosphate] exhibiting curative activity against chloroquine-resistant malaria parasites has been identified for preclinical development as a blood schizonticidal agent. The lead molecule selected after detailed structure-activity relationship (SAR) studies has good solid-state properties and promising activity against in vitro and in vivo experimental malaria models. The in vitro absorption, distribution, metabolism, and excretion (ADME) parameters indicate a favorable drug-like profile.
- Dola, Vasantha Rao,Soni, Awakash,Agarwal, Pooja,Ahmad, Hafsa,Raju, Kanumuri Siva Rama,Rashid, Mamunur,Wahajuddin, Muhammad,Srivastava, Kumkum,Haq,Dwivedi,Puri,Katti
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- A (S)- N - methoxy - methyl -2 - (tetrahydro-pyrrolyl) propionamide and its preparation method and application
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The invention discloses a (S)-N-methoxy-methyl-2-(pyrrolidine) propionamide shown as a formula (5). A preparation method is as follows: subjecting a starting material L-alanine to amino protection, reaction with N,O-dimethyl hydroxylamine hydrochloride, removal of amino protecting group, and alkylation; and subjecting the prepared compound shown as (5) to addition elimination and reduction to obtain an Efavirenz chiral ligand shown as the formula (7). The synthetic method of Efavirenz chiral ligand provided by the invention has the advantages of mild reaction conditions, simple operation, high yield and low production cost, and is suitable for industrialized production.
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Paragraph 0037; 0038
(2017/08/25)
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- Desyl and phenacyl as versatile, photocatalytically cleavable protecting groups: A classic approach in a different (visible) light
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A highly efficient, catalytic strategy for the deprotection of classical phenacyl (Pac) as well as desyl (Dsy) protection groups has been developed using visible light photoredox catalysis. The deliberate use of a neutral two-phase acetonitrile/water mixture with K3PO4 applying catalytic amounts of [Ru(bpy)3](PF6)2 in combination with ascorbic acid is the key to this truly catalytic deprotection of Pac- and Dsy-protected carboxylic acids. Our mild yet robust protocol allows for fast and selective liberation of the free carboxylic acids in very good to quantitative yields, while only low catalyst loadings (1 mol %) are required. Both Pac and Dsy, easily introduced from commercially available precursors, can be applied for the direct protection of carboxylic acids and amino acids, offering orthogonality to a great variety of other common protecting groups. We further demonstrate the general applicability and versatility of these formerly underrated protecting groups in combination with our catalytic cleavage conditions, as underscored by the gained high functional group tolerance. Moreover, this method could successfully be adapted to the requirements of solidphase synthesis. As a proof of principle for an efficient visible light, photocatalytic linker cleavage, a Boc-protected tripeptide was split off from commercially available brominated Wang resin.
- Speckmeier, Elisabeth,Zeitler, Kirsten
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p. 6821 - 6826
(2017/11/06)
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- PEPTIDOMIMETIC COMPOUNDS AND ANTIBODY-DRUG CONJUGATES THEREOF
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This invention relates to peptidomimetic linkers and anti-body drug conjugates thereof, to pharmaceutical compositions containing them, and to their use in therapy for the prevention or treatment of cancer.
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Page/Page column 110; 111
(2015/07/07)
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- Synthesis and applications in Henry reactions of novel chiral thiazoline tridentate ligands
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Several novel chiral tridentate ligands containing thiazoline were efficiently synthesized from commercially available l=cysteine in high yield. These ligands were subsequently applied to the asymmetric Henry reaction of nitromethane and various aldehydes. It was found that the structures of the thiazoline ligands had a significant influence on the enantioselectivity. It was shown that the optimal catalyst for this reaction was a ligand complexed with CuCl, which was formed from chiral thiazoline with chiral aminoalcohol. At -20°C, with 10 mol% of this ligand, a product with (S)-configuration was isolated in 93% yield and 98% enantiomeric excess.
- Shi, Ye,Li, Yang,Sun, Jingbo,Lai, Qi,Wei, Chiyu,Gong, Zhiyong,Gu, Qiang,Song, Zhiguang
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p. 661 - 667
(2015/09/28)
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- Autotandem catalysis: Synthesis of pyrroles by gold-catalyzed cascade reaction
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A novel synthesis of substituted pyrroles by a gold(I)-catalyzed cascade reaction has been developed. The reaction proceeded with an autotandem catalysis consisting of an initial addition of gold-acetylide to an acetal moiety and was followed by gold-catalyzed 5-endo-dig cyclization and aromatization. Gold catalysts play a dual role in activating nucleophilicity or electrophilicity of terminal acetylenes by forming gold-acetylides or by π-coordination. The formal (3 + 2) annulation of two components provided a variety of substituted pyrroles in a modular fashion.
- Ueda, Hirofumi,Yamaguchi, Minami,Kameya, Hiroshi,Sugimoto, Kenji,Tokuyama, Hidetoshi
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supporting information
p. 4948 - 4951
(2015/04/27)
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- Synthesis of enantiopure free and N-benzyloxycarbonyl-protected 3-substituted homotaurines from naturally occurring amino acids
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Enantiopure N-benzyloxycarbonyl-protected and free 3-substituted homotaurines were synthesized from naturally occurring amino acids via N-benzyloxycarbonyl protection, Arndt-Eistert homologation, reduction, esterification with thioacetic acid, and oxidation with performic acid. The current method is a convenient, practical, and salt-free method for the synthesis of enantiopure 3-substituted homotaurine with moderate to good yields.
- Zheng, Yongpeng,Xu, Jiaxi
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p. 5197 - 5206
(2014/12/10)
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- A palladium nanoparticle-nanomicelle combination for the stereo-selective semihydrogenation of alkynes in water at room temperature
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The addition of NaBH4 to Pd(OAc) 2 in water containing nanomicelles leads to the generation of H2 and Pd nanoparticles. Subsequent reduction of disubstituted alkynes affords Z-alkenes in high yields. These reactions are general, take place in water at ambient temperatures, and offer recycling of the aqueous reaction mixture along with low overall E Factors.
- Slack, Eric D.,Gabriel, Christopher M.,Lipshutz, Bruce H.
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supporting information
p. 14051 - 14054
(2015/02/19)
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- Photoinduced release of neurotransmitter amino acids from coumarin-fused julolidine ester cages
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The photoinduced release of several neurotransmitter amino acids (glycine, alanine, glutamic acid, β-alanine and γ-aminobutyric acid) was accomplished from ester cages based on a new photoremovable protecting group consisting of a coumarin built on the julolidine nucleus, namely a (11-oxo-2,3,5,6,7,11-hexahydro-1H-pyrano[2,3-f]pyrido[3,2,1-ij]quinolin-9-yl) methyl group. Photolysis and steady-state sensitization studies revealed that release of the active molecule occurred in short irradiation times at long wavelengths, with a very promising performance at 419 nm. Given the interest in the development of novel protecting groups that are cleavable with UV A or even visible radiation, it was found that a structural modification in the coumarin ring by assembly of a fused julolidine leads to a promising photolabile protecting group for organic synthesis and also for bioapplications. Photolysis and steady-state sensitization studies of several neurotransmitter amino acids from ester cages based on a new photoremovable protecting group consisting of a coumarin-fused julolidine nucleus, revealed that the release of the active molecule occurred in short irradiation times at long wavelengths, especially at 419 nm. Copyright
- Piloto, Ana M.,Hungerford, Graham,Costa, Susana P. G.,Goncalves, M. Sameiro T.
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p. 7715 - 7723
(2013/12/04)
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- Protecting-group-free total synthesis of (-)-rhazinilam and (-)-rhazinicine using a gold-catalyzed cascade cyclization
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'Rhaz'zmatazz: A total synthesis of (-)-rhazinilam and the first asymmetric total synthesis of (-)-rhazinicine were accomplished by using constructing the indolizinone core through the gold-catalyzed cyclization of a fully elaborated linear ynamide. The scope and generality of this cascade reaction for the construction of highly substituted indolizinones were also investigated. Copyright
- Sugimoto, Kenji,Toyoshima, Kazuki,Nonaka, Shiori,Kotaki, Kenta,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 7168 - 7171
(2013/07/26)
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- Unusual reactivity of dimethylsulfoxonium methylide with esters
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The dimethylsulfoxonium methylide was treated with esters under mild conditions to rapidly afford the corresponding carboxylic acids at room temperature. Moreover, by performing the procedure on enantiopure substrates, it was demonstrated that the reaction occurs without racemization. 18O-labeled reagents showed that the reaction does not proceed through an ester hydrolysis mechanism. The reactions are characterized by an unusual reactivity of the dimethylsulfoxonium methylide. This methodology is general and can be considered a valid alternate route for ester cleavage when a substrate is sensitive to hydrolysis conditions.
- Leggio, Antonella,De Marco, Rosaria,Perri, Francesca,Spinella, Mariagiovanna,Liguori, Angelo
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supporting information; experimental part
p. 114 - 118
(2012/02/14)
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- Regioselective double Boekelheide reaction: First synthesis of 3,6-dialkylpyrazine-2,5-dicarboxaldehydes from dl-alanine
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Pyrazine-2,5-dicarboxaldehyde was synthesized on a multi-gram scale by MnO2 oxidation of 2,5-bis(hydroxymethyl)pyrazine, which in turn was obtained from 2,5-dimethylpyrazine employing double Boekelheide reaction as a key step as reported previously. This reaction was subsequently utilized in a regioselective fashion as a key step to synthesize efficiently, for the first time, 3,6-di(long-chain)alkylpyrazine-2,5-dicarboxaldehydes starting from dl-alanine. These monomers are certain to have importance as electron deficient and chemically versatile components for new materials development.
- Das, Sajal Kumar,Frey, Joseph
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scheme or table
p. 3869 - 3872
(2012/08/14)
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- A mild method for the cleavage of the 4-picolyloxy group with magnesium under neutral conditions
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A mild and efficient method for the selective hydrolysis of 4-picolyl esters with magnesium in methanol or water in the presence of other esters and sensitive protecting groups is described. 4-Picolyl aryl ethers and thioethers are also smoothly deprotected to give the corresponding phenols and thiophenols. Georg Thieme Verlag Stuttgart. New York.
- Zhu, Jianwei,Miao, Wenjun,Bao, Lingling,Ji, Tao,Tang, Guo,Xu, Pengxiang,Zhao, Yufen
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supporting information; experimental part
p. 142 - 144
(2012/02/04)
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- Identification of the amino acid labionin and its desulfurised derivative in the type-III lantibiotic LabA2 by means of GC/MS
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A GC-MS method for the rapid and unambiguous identification of the amino acid labionin (Lab) occurring in type-III lantibiotics is presented. This method will constitute a valuable tool for the characterisation and structure elucidation of labyrinthopeptins and their differentiation from lanthionine-type lantibiotics.
- Pesic, Alexander,Henkel, Maik,Suessmuth, Roderich D.
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supporting information; experimental part
p. 7401 - 7403
(2011/08/05)
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- Papain-catalyzed peptide bond formation: Enzyme-specific activation with guanidinophenyl esters
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The substrate mimetics approach is a versatile method for small-scale enzymatic peptide-bond synthesis in aqueous systems. The protease-recognized amino acid side chain is incorporated in an ester leaving group, the substrate mimetic. This shift of the specific moiety enables the acceptance of amino acids and peptide sequences that are normally not recognized by the enzyme. The guanidinophenyl group (OGp), a known substrate mimetic for the serine proteases trypsin and chymotrypsin, has now been applied for the first time in combination with papain, a cheap and commercially available cysteine protease. To provide insight in the binding mode of various Z-XAA-OGp esters, computational docking studies were performed. The results strongly point at enzyme-specific activation of the OGp esters in papain through a novel mode of action, rather than their functioning as mimetics. Furthermore, the scope of a model dipeptide synthesis was investigated with respect to both the amino acid donor and the nucleophile. Molecular dynamics simulations were carried out to prioritize 22 natural and unnatural amino acid donors for synthesis. Experimental results correlate well with the predicted ranking and show that nearly all amino acids are accepted by papain.
- de Beer, Roseri J.A.C.,Zarzycka, Barbara,Amatdjais-Groenen, Helene I.V.,Jans, Sander C.B.,Nuijens, Timo,Quaedflieg, Peter J.L.M.,van Delft, Floris L.,Nabuurs, Sander B.,Rutjes, Floris P.J.T.
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experimental part
p. 2201 - 2207
(2012/05/05)
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- Hexafluoro-2-propanol as a potent cosolvent for chemical ligation of membrane proteins
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The study on membrane proteins is an important challenge mainly because of their very poor solubility in various solvents. The traditional recombinant expression strategy and the native chemical ligation method both have difficulty in generating sufficient amounts of desired proteins with high efficiency. Previous studies have shown that multiply fluorinated alcohols exhibit good ability to dissolve difficult peptide sequences, especially hexafluoro-2- propanol (HFIP). In the present study we systematically studied the capability of solvents containing different percentage of HFIP in dissolving transmembrane peptides. Through both HPLC and UV analyses we concluded that 60% HFIP/8 M urea constituted a good solvent system. In this solvent system we also optimized conditions to perform native chemical ligation (NCL). Under the optimized conditions we successfully achieved NCL's for both dipeptide formation and the synthesis of a model protein (Trifolitoxin). These results suggested that HFIP was a potential cosolvent that could be used in the ligation of poorly soluble peptides for the generation of membrane proteins.
- Shen, Fei,Tang, Shan,Liu, Lei
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experimental part
p. 110 - 116
(2012/01/03)
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- 2-Oxo-2H-benzo[h]benzopyran as a new light sensitive protecting group for neurotransmitter amino acids
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Aiming at the development of new benzopyran-based photocleavable protecting groups, novel chloromethylated and hydroxymethylated 2-oxo-2H-benzo[h] benzopyran derivatives bearing a methoxy substituent were designed and used in the synthesis of a series of fluorescent bioconjugates, by linking through an ester or urethane bond to several model neurotransmitter amino acids (glycine, alanine, β-alanine and γ-aminobutyric acid, GABA). The resulting fluorescent bioconjugates with emission in the visible range and high fluorescent quantum yields, were subjected to photocleavage reaction in methanol/HEPES buffer (80:20) solution at different wavelengths of irradiation (250, 300, 350 and 419 nm) and photocleavage kinetic data were obtained.
- Soares, Ana M. S.,Costa, Susana P. G.,Goncalves, M. Sameiro T.
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experimental part
p. 121 - 133
(2010/09/07)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 51
(2010/12/31)
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- Addition of allylzinc to a-amino acid-derived imines: Synthesis of diamino alcohols by Hydroboration
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Imines obtained by condensation of Z-pro- tected or Boc-protected α-amino aldehydes with α-amino tert-butyl esters or with O-silyl-protected amino alcohols were reacted with preformed allyl zinc yielding homoal- lylamines with yields around 50% and selectivities ranging from 50:50 to 90:10. Hydroboration of the terminal double bond furnished diamino alcohols with yields up to 97%. The configuration of the substrates was determined by X-ray-crystallographic analysis of a hydroboration product and comparison of physical data. Springer-Verlag 2010.
- Virlouvet, Mickael,Goesmann, Helmut,Feldmann, Claus,Podlech, Joachim
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scheme or table
p. 177 - 198
(2010/08/05)
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- Oxazole light triggered protecting groups: Synthesis and photolysis of fused heteroaromatic conjugates
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Fused oxazole derivatives were synthesized and evaluated as new light triggered protecting groups by using amino acids as model bifunctional molecules. The photosensitivity of ester conjugates was tested under irradiation at 254, 300, and 350 nm. Oxazole
- Soares, Ana M.S.,Costa, Susana P.G.,Gonalves, M. Sameiro T.
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experimental part
p. 8189 - 8195
(2010/11/04)
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- FLUORENE COMPOUND
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Particular compounds having a fluorene skeleton are superior in broad utility and stability, as a protecting reagent for liquid phase synthesis of amino acids and/or peptides.
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- Development of new HPLC chiral stationary phases based on native and derivatized cyclofructans
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An unusual class of chiral selectors, cyclofructans, is introduced for the first time as bonded chiral stationary phases. Compared to native cyclofructans (CFs), which have rather limited capabilities as chiral selectors, aliphatic-and aromatic-functionalized CF6s possess unique and very different enantiomeric selectivities. Indeed, they are shown to separate a very broad range of racemic compounds. In particular, aliphatic-derivatized CF6s with a low substitution degree baseline separate all tested chiral primary amines. It appears that partial derivatization on the CF6 molecule disrupts the molecular internal hydrogen bonding, thereby making the core of the molecule more accessible. In contrast, highly aromaticfunctionalized CF6 stationary phases lose most of the enantioselective capabilities toward primary amines, however they gain broad selectivity for most other types of analytes. This class of stationary phases also demonstrates high "loadability" and therefore has great potential for preparative separations. The variations in enantiomeric selectivity often can be correlated with distinct structural features of the selector. The separations occur predominantly in the presence of organic solvents.
- Sun, Ping,Wang, Chunlei,Breitbach, Zachary S.,Zhang, Ying,Armstrong, Daniel W.
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experimental part
p. 10215 - 10226
(2010/05/01)
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- AmIno Acid Homologation by the Blaise Reaction: A new entry into nitrogen heterocycles
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(Chemical Equation Presented) A general strategy for the amino acid homologation via Blaise reaction and subsequent reduction is presented. This strategy involves the preparation of protected α-amino nitriles from the corresponding amino acids, followed by the zinc-mediated condensation of tert-butyl bromoacetate, to give the imidazolidones after iminozincate cyclization. Reduction gave the saturated imidazolidinones with cis or trans stereochemistry, depending on the reduction conditions. This strategy was applied to nonfunctionalized amino acids and to functionalized amino acids such as serine and aspartic acid. Additionally, acidic hydrolysis of cis or trans imidazolidinones to the corresponding chiral 4-aminopyrrolidones is described.
- Cam, Thuy Hoang,Bouillere, Francelin,Johannesen, Sine,Zulauf, Anais,Panel, Cecilia,Pouilhes, Annie,Gori, Didier,Alezra, Valerie,Kouklovsky, Cyrille
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scheme or table
p. 4177 - 4187
(2009/09/08)
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- Expedient solid-phase synthesis of both symmetric and asymmetric diol libraries targeting aspartic proteases
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C2-symmetric diols have been shown to be highly potent against HIV-1 protease (PR). However, gaining access to these compounds has been hampered by the need of multistep solution-phase reactions which are often tedious and inefficient. In this Letter, we have disclosed a solid-phase strategy for rapid preparation of small molecule-based, symmetric and asymmetric diols as potential HIV-1 protease inhibitors. Upon biological screening, we found one of them, SYM-5, to be a potent and selective inhibitor (Ki = 400 nM) against HIV-1 protease.
- Shi, Haibin,Liu, Kai,Leong, Wendy W.Y.,Yao, Shao Q.
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supporting information; experimental part
p. 3945 - 3948
(2010/03/30)
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- Synthesis and utilization of chiral α-methylated α-amino acids with a carboxyalkyl side chain in the design of novel Grb2-SH2 peptide inhibitors free of phosphotyrosine
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The growth factor receptor-bound protein 2 (Grb2) is an SH2 domain-containing docking module that represents an attractive target for anticancer therapeutic intervention. To improve the potency and bioavailability of the Grb2-SH2 inhibitors, the chiral α-methyl-α-carboxyalkyl amino acid [(α-Me)Aa] was designed to cover dual structural and functional features separately contributed by 1-aminocyclohexanecarboxylic acid (Ac6c) and α-aminoadipic acid (Adi) in position Y + 1. The enantiopure L(or D)-(α-Me)Aa bearing various chain length carboxylalkyl side chain was conveniently synthesized by an optimized oxazolidinone methodology. The incorporation of (S)-(α-Me)Aa into the non-pTyr-containing peptide framework with a 5-amino acid sequence binding motif of X-2-Leu- (3′-substituted-Tyr)0-X+1-Asn really improved the inhibitory activity, affording potent (R)-sulfoxide-bridged cyclic and an open-chain series of pentapeptide inhibitors of Grb2-SH2 domain (IC50 = 1.1-5.8 μM). More significantly, these (α-Me)Aa incorporated peptide inhibitors showed excellent activities in inhibiting the growth of erbB2-dependent MDA-MB-453 tumor cell lines with low micromolar IC50 values, owing to the reduced peptidic nature and absence of pTyr or pTyr mimetics.
- Long, Ya-Qiu,Xue, Ting,Song, Yan-Li,Liu, Zu-Long,Huang, Shao-Xu,Yu, Qiang
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experimental part
p. 6371 - 6380
(2009/10/17)
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- Resolution of non-proteinogenic amino acids via microbial lipase-catalyzed enantioselective transesterification
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A number of non-proteinogenic amino acids bearing aliphatic side chains were resolved with moderate to good enantioselectivities (E = 15-42) through the Burkholderia cepacia lipase-catalyzed enantioselective transesterification of the 2,2,2-trifluoroethyl esters of their N-benzyloxycarbonyl derivatives with methanol as a nucleophile in diisopropyl ether.
- Miyazawa, Toshifumi,Mio, Motoe,Watanabe, Yuko,Yamada, Takashi
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p. 219 - 224
(2008/09/20)
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- Molecular mechanism of physical gelation of hydrocarbons by fatty acid amides of natural amino acids
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A variety of fatty acid amides of different naturally occurring l-amino acids have been synthesized and they are found to form gels with various hydrocarbons. The gelation properties of these compounds were studied by a number of physical methods including FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, rheology, and it was found that gelation depended critically on the fatty acid chain length and the nature of the amino acid. Among them l-alanine based gelators were found to be the most efficient and versatile gelators as they self-assemble into a layered structure to form the gel network. Mechanisms for the assembly and formation of gels from these molecules are discussed.
- Pal, Asish,Ghosh, Yamuna K.,Bhattacharya, Santanu
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p. 7334 - 7348
(2008/02/04)
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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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- Method for synthesis of C2-symmetric diamino diol mediated by titanium complexes
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A method for synthesis of C2-symmetric diamino diol mediated by titanium complexes is provided. A substituted-L-phenylalaninal undergoes pinacol coupling to yield the corresponding C2-symmetric (1S,2R,3R,4S)-1,4-diamino 2,3-diol in the presence of Cp2TiCl2/ZnCl2 and zinc metal, mediated in good yield and highly selective. This titanium-catalyzed reaction yields diaminodiol, offering a convenient alternative method to the synthesis of C2-symmetric peptidic protease inhibitors. Consequently, the method allows to synthesize TL-3 via titanium complex in moderate yield.
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Page/Page column 2; 3
(2008/06/13)
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- Aqueous phase mono-protection of amines and amino acids as N-benzyloxycarbonyl derivatives in the presence of β-cyclodextrin
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A simple and selective protection of amines/amino acids with Cbz-Cl has been achieved in aqueous phase with catalytic amounts of β-cyclodextrin in high yields at room temperature. This reaction proceeds without the formation of any by-products and has advantages over existing methods.
- Pavan Kumar,Somi Reddy,Narender,Surendra,Nageswar,Rama Rao
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p. 6393 - 6396
(2007/10/03)
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- Synthesis of chiral tropopodands having l-amino acid moieties and ability of their metal complexes as an asymmetric catalyst
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Optical active tropopodans (10 and 11) having neutral l-amino acids and l-histidine moieties were synthesized. Within their metal complexes, Pd complexes of histidine-tropopodands (11b and 11c) bearing bulky amide moieties showed good ability as an asymmetric catalyst in conjugate addition.
- Sato, Ohki,Koshiba, Yusuke,Sagara, Satoshi,Okada, Katsuyoshi
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p. 529 - 533
(2007/10/03)
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- α-Chymotrypsin-catalyzed peptide synthesis in frozen aqueous solution using N-protected amino acid carbamoylmethyl esters as acyl donors
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A kinetically controlled peptide synthesis catalyzed by α-chymotrypsin was performed in frozen aqueous solution (ice, -24 °C). The yield of the peptide was significantly improved by the use of the carbamoylmethyl (Cam) ester as the acyl donor instead of the conventional ethyl ester. The peptide yield increased up to ca. 90% when N-benzyloxycarbonyl (CBZ)-Phe-OCam and H-Phe-NH2 were used as the acyl donor and nucleophile, respectively. Such an improvement of the peptide yield in ice was also observed in the coupling of other CBZ-amino acid Cam esters as acyl donors. Furthermore, this approach was applied to the synthesis of peptides containing d-amino acids. The peptides such as CBZ-d-Phe-Phe-NH2, CBZ-Phe-d-Phe-NH2 and CBZ-d-Phe-d-Phe-NH2 were also obtained in excellent to moderate yields in ice. A high diastereoselectivity towards the l-l peptide was observed when the racemic amino acid Cam ester was used as the acyl donor in ice.
- Salam, Sayed Mohiuddin Abdus,Kagawa, Ken-Ichi,Kawashiro, Katsuhiro
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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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- Synthesis and pharmacological evaluation of glycine-modified analogues of the neuroprotective agent glycyl-L-prolyl-L-glutamic acid (GPE)
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The synthesis of 10 G*PE analogues, wherein the glycine residue has been modified, is described by coupling readily accessible dibenzyl-l-prolyl-l- glutamate 2 with various analogues of glycine. Pharmacological evaluation of the novel compounds was undertaken to further understand the role of the glycine residue on the observed neuroprotective properties of the endogenous tripeptide GPE.
- Lai, Michelle Y.H.,Brimble, Margaret A.,Callis, David J.,Harris, Paul W.R.,Levi, Mark S.,Sieg, Frank
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p. 533 - 548
(2007/10/03)
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- Resolution of non-protein amino acids via Carica papaya lipase-catalyzed enantioselective transesterification
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Carica papaya lipase-catalyzed transesterification of the 2,2,2-trifluoroethyl esters of N-benzyloxycarbonylated dl-amino acids carrying aliphatic side chains proceeded smoothly and, in almost all the cases, enantiospecifically (E = >200), affording the l-methyl esters and leaving the d-trifluoroethyl esters intact.
- Miyazawa, Toshifumi,Onishi, Kazuki,Murashima, Takashi,Yamada, Takashi,Tsai, Shau-Wei
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p. 2569 - 2573
(2007/10/03)
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- Optically active tropocoronands having amino acid residues in linker chains: Syntheses, metal coordination properties, and their abilities as an asymmetric catalyst
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Optically active tropocoronands (7) having l-amino acid moieties were synthesized by stepwise and one-pot reactions of tropolone derivatives with amino acid linker chains. The coordination styles of their Ni(II) and Pd(II) complexes and the abilities as an asymmetric catalyst were investigated.
- Sato, Ohki,Tanbo, Akira
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p. 357 - 366
(2007/10/03)
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