- Formal synthesis of aspidospermidine via the intramolecular cascade transannular cyclization
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A formal synthesis of aspidospermidine is reported through a novel preparation of Stork's penultimate tricyclic ketone intermediate. The key steps of the synthesis consist of an intramolecular cascade transannular cyclization, triggered by the removal of Boc group, which simultaneously forms the C, D, and E rings of aspidospermidine and conveniently setting up the quaternary stereocenter via decarboxylative alkylation reaction of the β-keto ester. Georg Thieme Verlag Stuttgart. New York.
- Huang, Jiu-Zhong,Jie, Xiao-Ke,Wei, Kun,Zhang, Hongbin,Wang, Min-Cai,Yang, Yu-Rong
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- Chiral tricyclic keto-amine compound as well as synthetic method and application thereof
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The invention discloses a chiral tricyclic keto-amine compound as well as a synthetic method and an application thereof. The invention discloses a (31S,6aR,9aR)-6a-ethyldecahydro-1H-pyrrolo-[3,2,1-ij]quinoline-9(2H)-ketone compound shown by a formula (1) and a preparation method thereof. According to the preparation method, the chiral tricyclic keto-amine compound is obtained through reactions of 5 steps of performing [4+2] cycloaddition on 3-ethyl-5-bromo-2-pyrone and (S)-2,3-dihydro-1H-pyrrole-1,2-di-tert-butyl dicarboxylate, performing decarboxylation, performing Pd/C catalytic hydrogenation and cyclization, and the like. The compound shown by the formula (1) is an advanced intermediate which can be used for preparing quebracho alkaloid, and the compound can be used for preparing the quebracho alkaloid and derivatives. The method starts from low-price and easily-available raw materials, and provides a good technical support for subsequent implementation of large-scale production and structure-activity relationship research of a quebracho alkaloid natural product.
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- Total Synthesis of (-)-Rhazinilam and Formal Synthesis of (+)-Eburenine and (+)-Aspidospermidine: Asymmetric Cu-Catalyzed Propargylic Substitution
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A total synthesis of (-)-rhazinilam and formal syntheses of (+)-eburenine and (+)-aspidospermidine that rely on a copper(I)-catalyzed asymmetric propargylic substitution as the key step are reported. A salient feature of the reaction is the asymmetric con
- Shemet, Andrej,Carreira, Erick M.
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p. 5529 - 5532
(2017/10/25)
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- Divergent Asymmetric Total Synthesis of (+)-Vincadifformine, (-)-Quebrachamine, (+)-Aspidospermidine, (-)-Aspidospermine, (-)-Pyrifolidine, and Related Natural Products
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A uniformly strategic total synthesis of Aspidosperma alkaloids (+)-vincadifformine, (-)-quebrachamine, (+)-aspidospermidine, (-)-aspidospermine, (-)-pyrifolidine, and nine others from efficiently constructed tricyclic ketone 13 is reported. Highlights of these divergent and practical syntheses include (i) stereoselective intermolecular [4 + 2] cycloaddition to establish a C-E ring with one all-carbon quaternary stereocenter (C-5) and two bridged contiguous cis-stereocenters (C-12 and C-19), (ii) a Pd/C-catalyzed hydrogenation/deprotection/amidation cascade process to assemble the D ring, and (iii) Fischer indolization to forge the A-B ring.
- Wang, Nengzhong,Du, Shuo,Li, Dong,Jiang, Xuefeng
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supporting information
p. 3167 - 3170
(2017/06/23)
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- Synthesis of biologically active natural products by [3?+?2] cycloaddition of non-stabilized azomethine ylides (AMY): Concepts and realizations
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Non-stabilized azomethine ylides (AMY) which are represented as a zwitterionic form of a C[sbnd]N[sbnd]C unit having four electrons in three parallel atomic π orbitals perpendicular to the plane of the dipole, undergoes 1,3-dipolar cycloaddition to produc
- Pandey, Ganesh,Dey, Debasis,Tiwari, Sandip Kumar
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p. 699 - 705
(2017/03/31)
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- Domino double Michael-Claisen cyclizations: A powerful general tool for introducing quaternary stereocenters at C(4) of cyclohexane-1,3-diones and total synthesis of diverse families of sterically congested alkaloids
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(Chemical Equation Presented) Reactions of substituted acetone derivatives with acrylic acid esters (>200 mol %) in the presence of t-BuOK (200 mol %) in t-BuOH-THF (1:1 by volume) turned out to proceed as a cascade process consisting of the first Michael addition, the second Michael addition, and the last Claisen reaction to afford 4,4-disubstituted cyclohexane-1,3-diones. Only more substituted enolates play the role of a Michael donor in this cascade process, and therefore the ketone took up two alkoxycarbonylethyl groups on the same carbon bearing more substituents. Such intermediates were followed by intramolecular Claisen reactions leading to cyclohexane-1,3-diones bearing quaternary stereogenic centers at C(4), which bears an alkoxycarbonylethyl group and the substituent of the starting acetone derivatives. Thus-obtained 4,4-disubstituted cyclohexane-1,3-diones were successfully employed for total syntheses of intricate alkaloids of biological interest such as (+)-aspidospermidine, (±)-galanthamine, (±)-lycoramine, and (±)-mesembrine, all featuring quaternary stereogenic centers. DFT calculations provided us with clear-cut explanations for the observed chemoselectivity of the cascade process involving ketone-based enolates under thermodynamically controlled conditions.
- Ishikawa, Teruhiko,Kudo, Kazuhiro,Kuroyabu, Ken,Uchida, Satoshi,Kudoh, Takayuki,Saito, Seiki
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p. 7498 - 7508
(2008/12/22)
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- Revisiting a classic approach to the Aspidosperma alkaloids: An intramolecular Schmidt reaction mediated synthesis of (+)-aspidospermidine
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A total synthesis of (+)-aspidospermidine (1) is described. The key reactions used in the synthesis of this pentacyclic Aspidosperma alkaloid were a deracemizing imine alkylation/Robinson annulation sequence, a selective "redox ketalization", and an intramolecular Schmidt reaction. A Fischer indolization step carried out on a tricyclic ketone mirrored the sequence reported by Stork and Dolfini in their classic aspidospermine synthesis.
- Iyengar, Rajesh,Schildknegt, Klaas,Morton, Martha,Aube, Jeffrey
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p. 10645 - 10652
(2007/10/03)
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- Total synthesis of (-)-aspidospermine via diastereoselective ring-closing olefin metathesis
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(Matrix presented) An enantiocontrolled total synthesis of (-)-aspidospermine has been achieved. The key element of the strategy is the diastereoselective construction of the quaternary stereogenic center employing 1,4-asymmetric induction during the ring-closing olefin metathesis.
- Fukuda, Yu-Ichi,Shindo, Mitsuru,Shishido, Kozo
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p. 749 - 751
(2007/10/03)
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- Regiocontrol in an Intramolecular Schmidt Reaction: Total Synthesis of (+)-Aspidospermidine
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(Matrix Presented) A total synthesis of (+)-aspidospermidine (1) is described, featuring an intramolecular Schmidt reaction as the key step. The effects of stereochemistry and protecting group status on the regio- and chemoselectivity of this reaction were examined.
- Iyengar, Rajesh,Schildknegt, Klaas,Aube?, Jeffrey
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p. 1625 - 1627
(2007/10/03)
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