共查询到20条相似文献,搜索用时 15 毫秒
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Sebastian Burck Dr. Sander G. A. van Assema Dr. Bas Lastdrager Dr. J. Chris Slootweg Dr. Andreas W. Ehlers Dr. José M. Otero Dr. Bruno Dacunha‐Marinho Dr. Antonio L. Llamas‐Saiz Dr. Mark Overhand Dr. Mark J. van Raaij Dr. Koop Lammertsma Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8134-8145
The natural product Gramicidin S is a promising scaffold for novel oligopeptide‐based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine‐containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the α‐carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single‐crystal X‐ray structure analysis. By detaching the template, enantiopure L ‐phosphine amino acids resulted enabling the solid‐phase, stepwise construction of a linear sequence of the phosphine‐modified oligopeptides. On cyclization three bisphosphine‐substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands. 相似文献
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Katsunori Tanaka Dr. Yohei Fujii Hiroomi Tokimoto Dr. Yasutaka Mori Shin‐ichi Tanaka Dr. Guang‐ming Bao Eric R. O. Siwu Dr. Aiko Nakayabu Koichi Fukase Prof. Dr. 《化学:亚洲杂志》2009,4(4):574-580
On solid ground : A new solid‐phase synthesis of N‐linked glycans featuring 1) highly stereoselective β‐mannosylation and microfluidic α‐sialylation and 2) efficient glycosylation of the N‐phenyltrifluoroacetimidate units on JandaJel resin is reported. Reagent concentration effects by a fluorous solvent are effectively applied, and the use of these methods results in the first synthesis of a sialic acid containing complex‐type N‐glycan on a solid support.
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Fustero S Sánchez-Roselló M Rodrigo V Sanz-Cervera JF Piera J Simón-Fuentes A del Pozo C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(23):7019-7029
The diastereoselective synthesis of cyclic beta,beta-difluorinated alpha-amino acid derivatives bearing a quaternary stereocenter is described. The process relies on the chemo- and diastereoselective addition of allylic organometallic reagents to fluorinated alpha-imino esters and a subsequent ring-closing metathesis reaction (RCM). Complete selectivity in the nucleophilic addition was achieved with (R)-phenylglycinol methyl ether as a chiral auxiliary. The resulting amino acids were introduced into peptide chains, which could facilitate the preparation of potentially bioactive dipeptide derivatives. In addition, the solution synthesis of these cyclic fluorinated alpha-amino acids was successfully adapted to solid-phase and fluorous-phase techniques. The reaction times and final deprotection were clearly more favorable in the latter, in which a fluorous trimethylsilylethanol (TMSE) tag was used. The tag was then easily removed upon treatment with TBAF in a high-yield transesterification process. 相似文献
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Stefan Brse Dieter Enders Johannes Kbberling Frank Avemaria 《Angewandte Chemie (International ed. in English)》1998,37(24):3413-3415
Triazenes as “traceless” linkers for solid-phase synthesis have been utilized for the attachment of arenes to a solid support and yield the corresponding products after various organometallic reactions (Heck reaction and asymmetric dihydroxylation, see the reaction scheme) and cycloadditions (Diels–Alder reaction). The triazene linker is distinguished by its accessibility, thermal robustness, and capability to undergo regeneration. 相似文献
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Liquid‐Phase Synthesis of 2′‐Methyl‐RNA on a Homostar Support through Organic‐Solvent Nanofiltration 下载免费PDF全文
Dr. Piers R. J. Gaffney Dr. Jeong F. Kim Irina B. Valtcheva Dr. Glynn D. Williams Dr. Mike S. Anson Dr. Andrew M. Buswell Prof. Andrew G. Livingston 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9535-9543
Due to the discovery of RNAi, oligonucleotides (oligos) have re‐emerged as a major pharmaceutical target that may soon be required in ton quantities. However, it is questionable whether solid‐phase oligo synthesis (SPOS) methods can provide a scalable synthesis. Liquid‐phase oligo synthesis (LPOS) is intrinsically scalable and amenable to standard industrial batch synthesis techniques. However, most reported LPOS strategies rely upon at least one precipitation per chain extension cycle to separate the growing oligonucleotide from reaction debris. Precipitation can be difficult to develop and control on an industrial scale and, because many precipitations would be required to prepare a therapeutic oligonucleotide, we contend that this approach is not viable for large‐scale industrial preparation. We are developing an LPOS synthetic strategy for 2′‐methyl RNA phosphorothioate that is more amenable to standard batch production techniques, using organic solvent nanofiltration (OSN) as the critical scalable separation technology. We report the first LPOS‐OSN preparation of a 2′‐Me RNA phosphorothioate 9‐mer, using commercial phosphoramidite monomers, and monitoring all reactions by HPLC, 31P NMR spectroscopy and MS. 相似文献
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Nicole Bzay Gregor Dudziak Andreas Liese Horst Kunz 《Angewandte Chemie (International ed. in English)》2001,40(12):2292-2295
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Rikard Wärme Lars Juhlin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2402-2408
Cyanuric fluoride, in solution or loaded onto a Wang resin, is successfully used as a fluorinating agent for phosphorus oxy acids. The reaction is very efficient with high yields and easy workup procedures, thereby in general generating products in quantitative yields. The cyanuric fluoride is proven suitable for micromolar scale synthesis of analytical standards, particularly in its resin-bound form. 相似文献
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Dr. Amy C. Topley Valerio Isoni Dr. Thomas A. Logothetis Dr. Duncan Wynn Dr. Harry Wadsworth Dr. Alex M. R. Gibson Imtiaz Khan Dr. Neil J. Wells Prof. Cécile Perrio Prof. Richard C. D. Brown 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1720-1725
A Resin‐linker‐vector (RLV) strategy is described for the radiosynthesis of tracer molecules containing the radionuclide 18F, which releases the labelled vector into solution upon nucleophilic substitution of a polystyrene‐bound arylsulfonate linker with [18F]‐fluoride ion. Three model linker‐vector molecules 7 a – c containing different alkyl spacer groups were assembled in solution from (4‐chlorosulfonylphenyl)alkanoate esters, exploiting a lipase‐catalysed chemoselective carboxylic ester hydrolysis in the presence of the sulfonate ester as a key step. The linker‐vector systems were attached to aminomethyl polystyrene resin through amide bond formation to give RLVs 8 a – c with acetate, butyrate and hexanoate spacers, which were characterised by using magic‐angle spinning (MAS) NMR spectroscopy. On fluoridolysis, the RLVs 8 a , b containing the longer spacers were shown to be more effective in the release of the fluorinated model vector (4‐fluorobutyl)phenylcarbamic acid tert‐butyl ester ( 9 ) in NMR kinetic studies and gave superior radiochemical yields (RCY≈60 %) of the 18F‐labelled vector. The approach was applied to the synthesis of the radiopharmaceutical O‐(2‐[18F]‐fluoroethyl)‐L ‐tyrosine ([18F]‐FET), delivering protected [18F]‐FET in >90 % RCY. Acid deprotection gave [18F]‐FET in an overall RCY of 41 % from the RLV. 相似文献
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Pierrick Nun Violaine Pérez Monique Calmès Jean Martinez Frédéric Lamaty 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3773-3779
The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase‐transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified. 相似文献
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Lukas Rigger Rachel L. Schmidt Kaitlyn M. Holman Prof. Miljan Simonović Prof. Dr. Ronald Micura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(47):15872-15878
The twenty first amino acid, selenocysteine (Sec), is the only amino acid that is synthesized on its cognate transfer RNA (tRNASec) in all domains of life. The multistep pathway involves O‐phosphoseryl‐tRNA:selenocysteinyl‐tRNA synthase (SepSecS), an enzyme that catalyzes the terminal chemical reaction during which the phosphoseryl–tRNASec intermediate is converted into selenocysteinyl‐tRNASec. The SepSecS architecture and the mode of tRNASec recognition have been recently determined at atomic resolution. The crystal structure provided valuable insights that gave rise to mechanistic proposals that could not be validated because of the lack of appropriate molecular probes. To further improve our understanding of the mechanism of the biosynthesis of selenocysteine in general and the mechanism of SepSecS in particular, stable tRNASec substrates carrying aminoacyl moieties that mimic particular reaction intermediates are needed. Here, we report on the accurate synthesis of methylated, phosphorylated, and phosphonated serinyl‐derived tRNASec mimics that contain a hydrolysis‐resistant ribose 3′‐amide linkage instead of the natural ester bond. The procedures introduced allow for efficient site‐specific methylation and/or phosphorylation directly on the solid support utilized in the automated RNA synthesis. For the preparation of (S)‐2‐amino‐4‐phosphonobutyric acid–oligoribonucleotide conjugates, a separate solid support was generated. Furthermore, we developed a three‐strand enzymatic ligation protocol to obtain the corresponding full‐length tRNASec derivatives. Finally, we developed an electrophoretic mobility shift assay (EMSA) for rapid, qualitative characterization of the SepSecS‐tRNA interactions. The novel tRNASec mimics are promising candidates for further elucidation of the biosynthesis of selenocysteine by X‐ray crystallography and other biochemical approaches, and could be attractive for similar studies on other tRNA‐dependent enzymes. 相似文献