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101.
Felix Krupp Wolfgang Frey Clemens Richert 《Angewandte Chemie (International ed. in English)》2020,59(37):15875-15879
The most reliable method to determine the absolute configuration of chiral molecules is X‐ray crystallography, but small molecules can be difficult to crystallize. We report rapid co‐crystallization of tetraaryladamantanes with small molecules as different as n‐decane to nicotine to produce crystals for X‐ray analysis and the assignment of absolute configuration when the molecules are chiral. A screen of 52 diverse compounds gave inclusion in co‐crystals for 88 % of all cases and a high‐resolution structure in 77 % of cases. Furthermore, starting from three milligrams of analyte, a combination of NMR spectroscopy and X‐ray crystallography produced a full structure in less than three days using an adamantane crystallization chaperone that encapsulates the analyte at room temperature. 相似文献
102.
Nicolas Armanino Julie Charpentier Felix Flachsmann Andreas Goeke Marc Liniger Philip Kraft 《Angewandte Chemie (International ed. in English)》2020,59(38):16310-16344
This review is the sequel to the 2000 report on the recent advances in the chemistry of odorants and it summarizes the developments in fragrance chemistry over the past 20 years. Following the olfactory spectrum set out in that report, trendsetting so‐called captive odorants (patent‐protected ingredients unavailable to the market) are presented according to the main odor families: “fruity”, “marine”, “green”, “floral”, “spicy”, “woody”, “amber”, and “musky”. The design of odorants, their chemical synthesis, and their use in modern perfumery are illustrated with prominent examples. Featured are new fruity odorants that provide signature in the top note, as well as precursor technology. In the green domain, focus is on leafy notes and green pear. New benzodioxepines and benzodioxoles have modernized the marine family and required a revision of the existing olfactophore models. The replacement of Lilial and Lyral kept the industry busy in the floral domain with a plethora of new “muguets”. There was continued activity in the domain of rose odorants, especially in the area of rose ketones. Biotechnology became significant, for example, with Clearwood and Ambrofix, and the principal odorants of vetiver oil in the woody family have been found. Fourth and fifth families of musk odorants were also discovered and populated. Thus, new avenues for further explorations into fragrance chemistry have been opened. 相似文献
103.
Felix Nußbaumer Raphael Plangger Manuel Roeck Christoph Kreutz 《Angewandte Chemie (International ed. in English)》2020,59(39):17062-17069
We present the access to [5‐19F, 5‐13C]‐uridine and ‐cytidine phosphoramidites for the production of site‐specifically modified RNAs up to 65 nucleotides (nts). The amidites were used to introduce [5‐19F, 5‐13C]‐pyrimidine labels into five RNAs—the 30 nt human immunodeficiency virus trans activation response (HIV TAR) 2 RNA, the 61 nt human hepatitis B virus ? (hHBV ?) RNA, the 49 nt SAM VI riboswitch aptamer domain from B. angulatum, the 29 nt apical stem loop of the pre‐microRNA (miRNA) 21 and the 59 nt full length pre‐miRNA 21. The main stimulus to introduce the aromatic 19F–13C‐spin topology into RNA comes from a work of Boeszoermenyi et al., in which the dipole‐dipole interaction and the chemical shift anisotropy relaxation mechanisms cancel each other leading to advantageous TROSY properties shown for aromatic protein sidechains. This aromatic 13C–19F labeling scheme is now transferred to RNA. We provide a protocol for the resonance assignment by solid phase synthesis based on diluted [5‐19F, 5‐13C]/[5‐19F] pyrimidine labeling. For the 61 nt hHBV ? we find a beneficial 19F–13C TROSY enhancement, which should be even more pronounced in larger RNAs and will facilitate the NMR studies of larger RNAs. The [19F, 13C]‐labeling of the SAM VI aptamer domain and the pre‐miRNA 21 further opens the possibility to use the biorthogonal stable isotope reporter nuclei in in vivo NMR to observe ligand binding and microRNA processing in a biological relevant setting. 相似文献
104.
Bhuvanesh Gupta Felix N. Büchi Markus Staub D. Grman Günther G. Scherer 《Journal of polymer science. Part A, Polymer chemistry》1996,34(10):1873-1880
The structure and some physico-chemical properties of radiation grafted FEP-g-polystyrenesulfonic acid proton exchange membranes were studied as a function of the degree of grafting. The distribution of grafted polymer across the membrane thickness was obtained from microprobe measurements. It was found that for low levels of grafting (ca. 3%), polystyrene chains are located near the membrane surface only, and the interior of the membrane remains ungrafted. With the increasing degree of grafting, polystyrene chains were incorporated into the interior of the membrane as well. An almost homogeneous distribution of grafts in the membrane was obtained at a graft level of > 13%. The influence of the degree of grafting on membrane properties, such as ion exchange capacity, swelling, and specific resistivity was studied. Three different states of water, viz., freezing free, freezing bound, and nonfreezing water have been identified in noncrosslinked membranes. However, the nature and the amount of crosslinker had a profound influence on the states of water in a membrane. © 1996 John Wiley & Sons, Inc. 相似文献
105.
106.
107.
Cover Picture: Total Synthesis of Resveratrol‐Based Natural Products Using a Palladium‐Catalyzed Decarboxylative Arylation and an Oxidative Heck Reaction (Angew. Chem. Int. Ed. 9/2014) 下载免费PDF全文
Felix Klotter Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2014,53(9):2253-2253
108.
Xin-Liang Li Lars G. Ljungdahl Eduardo A. Ximenes Huizhong Chen Carlos R. Felix Michael A. Cotta Bruce S. Dien 《Applied biochemistry and biotechnology》2004,113(1-3):233-250
A β-glucosidase (BglA, EC 3.2.1.21) gene from the polycentric anaerobic fungus Orpinomyces PC-2 was cloned and sequenced. The enzyme containing 657 amino acid residues was homologous to certain animal, plant, and
bacterial β-glucosidases but lacked significant similarity to those from aerobic fungi. Neither cellulose- nor protein-binding
domains were found in BglA. When expressed in Saccharomyces cerevisiae, the enzyme was secreted in two forms with masses of about 110 kDa and also found in two forms associated with the yeast
cells. K
m
and V
max
values of the secreted BglA were 0.762 mM and 8.20 μmol/(min·mg), respectively, with p-nitrophenyl-β-d-glucopyranoside (pNPG) as the substrate and 0.310 mM and 6.45 μmol/(min·mg), respectively, for the hydrolysis of cellobiose. Glucose competitively inhibited the hydrolysis of
pNPG with a K
i
of 3.6 mM. β-Glucosidase significantly enhanced the conversion of cellulosic materials into glucose by Trichoderma reesei cellulase preparations, demonstrating its potential for use in biofuel and feedstock chemical production.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may be
suitable. 相似文献
109.
Metal‐Free Catalyst for the Chemoselective Methylation of Amines Using Carbon Dioxide as a Carbon Source 下载免费PDF全文
Dr. Shoubhik Das Felix D. Bobbink Prof. Dr. Gabor Laurenczy Prof. Dr. Paul J. Dyson 《Angewandte Chemie (International ed. in English)》2014,53(47):12876-12879
N‐methylation of amines is an important step in the synthesis of many pharmaceuticals and has been widely applied in the preparation of other key intermediates and chemicals. Therefore, the development of efficient methylation methods has attracted considerable attention. In this respect, carbon dioxide is an attractive C1 building block because it is an abundant, renewable, and nontoxic carbon source. Consequently, we developed a highly chemoselective, metal‐free catalytic system that operates under ambient conditions for the N‐methylation of amines. 相似文献
110.
Synthesis and EPR/UV/Vis‐NIR Spectroelectrochemical Investigation of a Persistent Phosphanyl Radical Dication 下载免费PDF全文
Kai Schwedtmann Stephen Schulz Felix Hennersdorf Prof. Dr. Thomas Strassner Dr. Evgenia Dmitrieva Prof. Dr. Jan J. Weigand 《Angewandte Chemie (International ed. in English)》2015,54(38):11054-11058
The reaction of the bis(imidazoliumyl)‐substituted PI cation [(2‐ImDipp)P(4‐ImDipp)]+ ( 10 +) (2‐Im=imidazolium‐2‐yl; 4‐Im=imidazolium‐4‐yl; Dipp=2,6‐di‐isopropylphenyl) with trifluoromethanesulfonic acid (HOTf) or methyl trifluoromethylsulfonate (MeOTf) yields the corresponding protonated [(2‐ImDipp)PH(4‐ImDipp)]2+ ( 11 2+) and methylated [(2‐ImDipp)PMe(4‐ImDipp)]2+ ( 12 2+) dications, respectively. EPR/UV/Vis‐NIR spectroelectrochemical investigation of the low‐coordinated PI cation 10 + predicted a stable and “bottleable” P‐centered radical dication [(2‐ImDipp)P(4‐ImDipp)]2+. ( 13 2+.). The reaction of 10 + with the nitrosyl salt NO[OTf] yields the persistent phosphanyl radical dication 13 2+. as triflate salt in crystalline form. Quantum chemical investigation revealed an exceptional high spin density at the P atom. 相似文献