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881.
Benjamin Doistau Arnaud Tron Dr. Sergey A. Denisov Dr. Gediminas Jonusauskas Dr. Nathan D. McClenaghan Geoffrey Gontard Dr. Valérie Marvaud Prof. Dr. Bernold Hasenknopf Dr. Guillaume Vives 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15799-15807
The design and synthesis of switchable molecular tweezers based on a luminescent terpy(Pt‐salphen)2 ( 1 ; terpy=terpyridine) complex is reported. Upon metal coordination, the tweezers can switch from an open “W”‐shaped conformation to a closed “U”‐shaped form that is adapted for selective recognition of cations. Closing of the tweezers by metal coordination (M=Zn2+, Cu2+, Pb2+, Fe2+, Hg2+) was monitored by 1H NMR and/or UV/Vis titrations. During the titration, exclusive formation of the 1:1 complex [M( 1 )] was observed, without appearance of an intermediate 1:2 complex [M( 1 )2]. The crystallographic structure of the 1:1 complex was obtained with Pb2+ and showed a distorted helical structure. Selective intercalation of Hg2+ cations by the closed “U” form was observed. The tweezers were reopened by selective metal decoordination of the terpyridine ligand by using tris(2‐aminoethyl)amine (tren) as a competitive ligand without modification of the Pt–salphen complex. Detailed photophysical studies were performed on the open and closed tweezers. Structured emission was observed in the open form from the Pt–salphen moieties, with a high quantum yield and a long lifetime. The emission is slightly modified upon closing with 1 equivalent of Zn2+ or Hg2+, whereas a dramatic quenching was obtained upon intercalation of additional Hg2+. 相似文献
882.
Diastereoselective Synthesis of Open‐Chain Secondary Alkyllithium Compounds and Trapping Reactions with Electrophiles 下载免费PDF全文
Dr. Guillaume Dagousset Kohei Moriya Rasmus Mose Dr. Guillaume Berionni Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2014,53(5):1425-1429
A practical stereoselective iodide–lithium exchange was used in the first general preparation of functionalized stereodefined acyclic secondary nonstabilized lithium reagents from the corresponding secondary alkyl iodides. These lithium reagents react with various electrophiles including carbon electrophiles with high retention of configuration. Kinetic data on the configurational stability of these acyclic alkyllithium reagents are given. This methodology offers a new entry to chiral synthons for the stereoselective synthesis of open‐chain molecules. 相似文献
883.
Spontaneous Biomimetic Formation of (±)‐Dictazole B under Irradiation with Artificial Sunlight 下载免费PDF全文
Adam Skiredj Dr. Mehdi A. Beniddir Prof. Dr. Delphine Joseph Karine Leblanc Dr. Guillaume Bernadat Dr. Laurent Evanno Prof. Dr. Erwan Poupon 《Angewandte Chemie (International ed. in English)》2014,53(25):6419-6424
Guided by biosynthetic considerations, the total synthesis of dictazole B is reported for the first time. Experimental evidence for an easy access to challenging cyclobutane alkaloids of marine origin, which are often postulated to be biosynthetic precursors of more complex structures, is provided. 相似文献
884.
Dr. Martin Rahm Guillaume Bélanger‐Chabot Prof. Ralf Haiges Prof. Karl O. Christe 《Angewandte Chemie (International ed. in English)》2014,53(27):6893-6897
The elusive nitryl cyanide, NCNO2, has been synthesized and characterized. It was prepared in good yield, isolated by fractional condensation, characterized by NMR and vibrational spectroscopy, and studied by theoretical calculations. Nitryl cyanide holds promise as a high energy density material (HEDM) and might also prove useful as a HEDM building block. The simplicity and inherent stability of nitryl cyanide, together with the known multitude of nitriles in interstellar space, suggest that the compound might also be a potential candidate for observations in atmospheric and interstellar chemistry. 相似文献
885.
From Chitin to Bioactive Chitooligosaccharides and Conjugates: Access to Lipochitooligosaccharides and the TMG‐chitotriomycin 下载免费PDF全文
Guillaume Despras Aurélien Alix Dominique Urban Boris Vauzeilles Jean‐Marie Beau 《Angewandte Chemie (International ed. in English)》2014,53(44):11912-11916
The direct and chemoselective N‐transacylation of peracetylated chitooligosaccharides (COSs), readily obtained from chitin, to give per‐N‐trifluoroacetyl derivatives offers an attractive route to size‐defined COSs and derived glycoconjugates. It involves the use of various acceptor building blocks and trifluoromethyl oxazoline dimer donors prepared with efficiency and highly reactive in 1,2‐trans glycosylation reactions. This method was applied to the preparation of the important symbiotic glycolipids which are highly active on plants and to the TMG‐chitotriomycin, a potent and specific inhibitor of insect, fungal, and bacterial N‐acetylglucosaminidases. 相似文献
886.
Guillaume Robichaud Jeremy A. Barry Kenneth P. Garrard David C. Muddiman 《Journal of the American Society for Mass Spectrometry》2013,24(1):92-100
Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling.
Design and integration of a versatile IR-MALDESI imaging source offering multi-shot capability with a commercial FT-ICR mass spectrometer 相似文献
887.
Aurlien Chardon Arnaud Osi Damien Mahaut Thu‐Hong Doan Nikolay Tumanov Johan Wouters Luca Fusaro Benoît Champagne Guillaume Berionni 《Angewandte Chemie (International ed. in English)》2020,59(30):12402-12406
A highly bent triarylborane, 9‐boratriptycene, was generated in solution by selective protodeboronation of the corresponding tetra‐aryl boron ate complex with the strong Brønsted acid HNTf2. The iptycene core confers enhanced Lewis acidity to 9‐boratriptycene, making it unique in terms of structure and reactivity. We studied the stereoelectronic properties of 9‐boratriptycene by quantifying its association with small N‐ and O‐centered Lewis bases, as well as with sterically hindered phosphines. The resultant Lewis adducts exhibited unique structural, spectroscopic, and photophysical properties. Beyond the high pyramidalization of the 9‐boratriptycene scaffold and its low reorganization energy upon Lewis base coordination, quantum chemical calculations revealed that the absence of π donation from the triptycene aryl rings to the boron vacant pz orbital is one of the main reasons for its high Lewis acidity. 相似文献
888.
889.
Yingchao Dou Cyrille Kouklovsky Vincent Gandon Guillaume Vincent 《Angewandte Chemie (International ed. in English)》2020,59(4):1527-1531
The first total synthesis of the caged monoterpene indole alkaloid cymoside is reported. This natural product displays a unique hexacyclic‐fused skeleton whose biosynthesis implies an early oxidative cyclization of strictosidine. Our approach to the furo[3,2‐b]indoline framework relied on an unprecedented biomimetic sequence which started by the diastereoselective oxidation of the indole ring into a hydroxyindolenine which triggered the addition of an enol ether and was followed by the trapping of an oxocarbenium intermediate. 相似文献
890.
Thomas Varlet Coralie Gelis Pascal Retailleau Guillaume Bernadat Luc Neuville Graldine Masson 《Angewandte Chemie (International ed. in English)》2020,59(22):8491-8496
An efficient enantioselective construction of tetrahydronaphthalene‐1,4‐diones as well as dihydronaphthalene‐1,4‐diols by a chiral phosphoric acid catalyzed quinone Diels–Alder reaction with dienecarbamates is reported. The nature of the protecting group on the diene is key to the success of achieving high enantioselectivity. The divergent “redox” selectivity is controlled by using an adequate amount of quinones. Reversible redox switching without erosion of enantioselectivity was possible from individual redox isomers. 相似文献