Protecting‐Group‐Free Total Synthesis of (−)‐Rhazinilam and (−)‐Rhazinicine using a Gold‐Catalyzed Cascade Cyclization

Sugimoto, Kenji; Toyoshima, Kazuki; Nonaka, Shiori; Kotaki, Kenta; Ueda, Hirofumi; Tokuyama, Hidetoshi

doi:10.1002/ange.201303067

Cited by 25 publications

(5 citation statements)

References 52 publications

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“…Der goldene Ringschluss: Gleich mehrere Arbeitsgruppen setzten im letzten Jahr erfolgreich goldkatalysierte kaskadenartige Cyclisierungen in der Alkaloidsynthese ein. Die Arbeitsgruppe um Tokuyama entwickelte und optimierte hierfür extra eine neuartige Ringschlussreaktion,22 um aus linearen Vorläufern über eine sequenzielle Reaktionskaskade das bicyclische 5‐Indolizinon (23) aufzubauen (Abbildung 11, S. 268) 23. Der Inamidbaustein (24), der bereits alle nötigen Kohlenstoffatome für den späteren Naturstoff enthält, wurde in einer neunstufigen Reaktionssequenz erhalten.…”

Section: Naturstoff(total)syntheseunclassified

Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI

Feng

Zhu

et al. 2015

Chemistry A European J

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Diamagnetic chemical exchange saturation transfer (CEST) contrast agents offer an alternative to Gd3+-based contrast agents for MRI. They are characterized by containing protons that can rapidly exchange with water and it is advantageous to have these protons resonate in a spectral window that is far removed from water. Here, we report the first results of DFT calculations of the 1H nuclear magnetic shieldings in 41 CEST agents, finding that the experimental shifts can be well predicted (R2 = 0.882). We tested a subset of compounds with the best MRI properties for toxicity and for activity as uncouplers, then obtained mice kidney CEST MRI images for three of the most promising leads finding 16 (2,4-dihydroxybenzoic acid) to be one of the most promising CEST MRI contrast agents to date. Overall, the results are of interest since they show that 1H NMR shifts for CEST agents—charged species—can be well predicted, and that several leads have low toxicity and yield good in vivo MR images.

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Section: Naturstoff(total)syntheseunclassified

Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI

Feng

Zhu

et al. 2015

Chemistry A European J

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“…The successful development of an alkynyl Heck reaction would allow direct access to chiral β-alkynyl carbonyl compounds, which are versatile intermediates that have extensive applications in organic synthesis. [6] Traditionally, these types of compounds have been synthesized using enantioselective conjugate addition technologies, pioneered by Carreira, [7] Hayashi, [8] and others, through organometallic acetylide addition to α,β-unsaturated carbonyl substrates. [9] However, we envisioned that a redox-relay Heck approach that utilized allylic alcohol substrates would provide an attractive alternative to this field due to the ease of preparation, handling and improved stability of such alkenols.…”

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confidence: 99%

Palladium‐Catalyzed Enantioselective Redox‐Relay Heck Alkynylation of Alkenols To Access Propargylic Stereocenters

et al. 2017

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“…During the course of our continuing studies on the synthesis of monoterpene indole alkaloids,3 we recently established a highly efficient synthesis of substituted indolizidines via a gold‐catalyzed double cyclization cascade3c (Scheme ). One of the advantages of this cascade reaction is the facile preparation of completely functionalized acyclic substrates with the required substituents by assembling three components in modular fashion, which results in multi‐substituted indolizidines after a simple one‐pot operation.…”

Section: Methodsmentioning

confidence: 99%

“…One of the advantages of this cascade reaction is the facile preparation of completely functionalized acyclic substrates with the required substituents by assembling three components in modular fashion, which results in multi‐substituted indolizidines after a simple one‐pot operation. The utility of this reaction was demonstrated by our total synthesis of (−)‐rhazinilam and the first asymmetric total synthesis of (−)‐rhazinicine 3c…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Substituted Quinolizidines via a Gold‐Catalyzed Double Cyclization Cascade

et al. 2016

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An ovels ynthesis of quinolizidinesb y ac ationic gold-catalyzed double cyclization cascade has been developed. Ther eactionw as initiated by the gold-catalyzed 6-exo-dig cyclization of ynamides,w hich was followed by as econd cyclization of an enamide intermediate to provide the corresponding quinolizidine derivatives.T he utility of this reactionw as demonstratedb ya pplicationt o the synthesis of multi-substituted quinolizidines and by the total synthesiso faquinolizidine alkaloid, (AE)-lupinine.Keywords: alkaloids;c yclization;d omino reaction; gold;quinolizidines Numerous alkaloids containingaq uinolizidine (octahydro-2H-quinolizine,n orlupinane) core (Figure 1), including cytosine and sparteine,h ave been found in Nature.[1] Because members of this class of natural productso ften possess diverse and important biological activities, these compoundsh ave attracted broad interest from the synthesis community and have provided an attractivep latform to demonstrate the utility of novels ynthetic methodologies and tactics. Oneo f the conventional strategies to prepare this nitrogencontainingb icyclic heterocycle is fusion of the second ring on ap iperidine ring with installationo fp eripheral substituents or conversion of pyridine derivatives to bicyclic compounds,a nd subsequent hydrogenation of the pyridine ring.[2] Theses tepwises trategies generally require lengthys equences andc areful stereocontrol and/or regiocontrol for introducing the requisite functionalitiesa tt he desired positions,w hich is not always astraightforward task.During the course of our continuing studies on the synthesiso fm onoterpene indole alkaloids, [3] we recently established ah ighly efficient synthesis of substitutedi ndolizidines via ag old-catalyzed double cyclization cascade [3c] (Scheme 1). Oneo ft he advantages of this cascade reactioni st he facile preparation of completely functionalized acyclic substratesw ith the requireds ubstituents by assembling three components in modular fashion,w hich results in multi-substituted indolizidines after as impleo ne-pot operation. The utility of this reactionw as demonstrated by our total

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Protecting‐Group‐Free Total Synthesis of (−)‐Rhazinilam and (−)‐Rhazinicine using a Gold‐Catalyzed Cascade Cyclization

Cited by 25 publications

References 52 publications

Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI

Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI

Palladium‐Catalyzed Enantioselective Redox‐Relay Heck Alkynylation of Alkenols To Access Propargylic Stereocenters

Synthesis of Substituted Quinolizidines via a Gold‐Catalyzed Double Cyclization Cascade

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