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《Chemie in Unserer Zeit》2018,52(4):238-248
Quinine, isolated in pure form already in 1820 is a medication that was and is used to treat malaria since centuries. As its source, the cinchona tree, it is a legend and of utmost medical benefit until today. We present excerpts of reviews, which describe the background story of cinchona tree, and quinine as well as of the efforts made for isolation, structure elucidation and total synthesis of this alkaloid. This illustrates how this work forwarded organic chemistry as a whole. A possible personal uptake of quinine as bitter substance is discussed, looking at Tonic Water, Gin Tonic, and their impressive blue fluorescence under UV irradiation. Other uses of quinine in pharmacy and organic synthesis are shown. We describe the isolation of pure quinine from cinchona bark and present its complete set of spectra together with interpretations. Based on a laboratory project this paper is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009). 相似文献
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Bo Xu Bingyang Wang Wen Xun Fayang G. Qiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5810-5813
A concise and highly stereoselective total synthesis of the Daphniphyllum alkaloids (?)‐daphenylline has been accomplished. The synthesis was started from (S)‐carvone and proceeded via a stereoselective Mg(ClO4)2‐catalyzed intramolecular amide addition cyclization, an intramolecular Diels–Alder reaction to construct the ABCD tetracyclic core architecture, and a Robinson annulation coupled with an oxidative aromatization sequence. Finally, the DF ring system was installed through an intramolecular Friedel–Crafts cyclization. The total synthesis of (?)‐daphenylline is achieved in 19 steps in the longest reaction sequence and in 7.6 % overall yield. 相似文献
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Meike Sapotta Anja Hofmann David Bialas Frank Würthner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3554-3558
Herein, we report a water‐soluble macrocyclic host based on perylene bisimide (PBI) chromophores that recognizes natural aromatic alkaloids in aqueous media by intercalating them into its hydrophobic cavity. The host–guest binding properties of our newly designed receptor with several alkaloids were studied by UV/Vis and fluorescence titration experiments as the optical properties of the chromophoric host change significantly upon complexation of guests. Structural information on the host–guest complexes was obtained by 1D and 2D NMR spectroscopy and molecular modelling. Our studies reveal a structure–binding property relationship for a series of structurally diverse aromatic alkaloids with the new receptor and higher binding affinity for the class of harmala alkaloids. To our knowledge, this is the first example of a chromophoric macrocyclic host employed as a molecular probe for the recognition of aromatic alkaloids. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9190-9194
Hapalindole U ( 4 ) is a validated biosynthetic precursor to ambiguine alkaloids (Angew. Chem. Int. Ed . 2016 , 55 , 5780), of which biogenetic origin remains unknown. The recent discovery of AmbU4 (or FamC1) protein encoded in the ambiguine biosynthetic pathway (J. Am. Chem. Soc . 2015 , 137 , 15366), an isomerocyclase that can rearrange and cyclize geranylated indolenine ( 2 ) to a previously unknown 12‐epi ‐hapalindole U ( 3 ), raised the question whether 3 is a direct precursor to 4 or an artifact arising from the limited in vitro experiments. Here we report a systematic approach that led to the discovery of an unprecedented calcium‐dependent AmbU1‐AmbU4 enzymatic complex for the selective formation of 4 . This discovery refuted the intermediacy of 3 and bridged the missing links in the early‐stage biosynthesis of ambiguines. This work further established the isomerocyclases involved in the biogenesis of hapalindole‐type alkaloids as a new family of calcium‐dependent enzymes, where the metal ions are shown critical for their enzymatic activities and selectivities. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3757-3761
The asymmetric total syntheses of a group of structurally complex Kopsia alkaloids, (−)‐kopsine, (−)‐isokopsine, (+)‐methyl chanofruticosinate, (−)‐fruticosine, and (−)‐kopsanone, has been achieved. The key strategies for the construction of the molecular complexity in the targets included an asymmetric Tsuji–Trost rearrangement to set the first quaternary carbon center at C20, an intramolecular cyclopropanation by diazo decomposition to install the second and third quaternary carbon centers at C2 and C7, respectively, and a SmI2‐promoted acyloin condensation to assemble the isokopsine core. A radical decarboxylation of an isokopsine‐type intermediate results in a thermodynamic partial rearrangement to give N‐decarbomethoxyisokopsine and N‐decarbomethoxykopsine, two key intermediates for the syntheses of Kopsia alkaloids with different subtype core structures. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):10970-10974
The total synthesis of (−)‐virosaine A ( 1 ) was achieved in ten steps starting from furan and 2‐bromoacrolein. A one‐pot Diels–Alder cycloaddition/organolithium addition initiated an efficient sequence to access a key oxime/epoxide intermediate. Heating this intermediate in acetic acid resulted in an intramolecular epoxide opening/nitrone [3+2] cycloaddition cascade to construct the caged core of 1 in a single step. Several methods of C−H functionalization were assessed on the cascade product, and ultimately, a directed lithiation/bromination effected selective C14 functionalization, enabling the synthesis of 1 . 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(45):14425-14428
Here we report asymmetric total syntheses of communesin F and a putative member of the communesin family of bis‐aminal alkaloid natural products. The successful strategy featured the invention of an asymmetric organocatalytic reaction to unify two oxindole subunits, a Ti(OiPr)4‐mediated dehydrative skeletal rearrangement, and a late‐stage Pd(OAc)2‐catalyzed directed CH‐alkenylation reaction. Collectively, the synthetic technologies disclosed herein enabled the preparation of a late‐stage polycyclic intermediate catered for the synthesis of both naturally occurring and designed communesins. More importantly, speculated and yet to be discovered member(s) of the communesin family can now be accessed to facilitate a better understanding of the communesin biosynthetic network. 相似文献
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