- Efficient and Practical Syntheses of Enantiomerically Pure (S)-(-)-Norcryptostyline I, (S)-(-)-Norcryptostyline II, (R)-(+)-Salsolidine and (S)-(-)-Norlaudanosine via a Resolution-Racemization Method
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Four racemic tetrahydroisoquinolines (RS)-(±)-1-4 were prepared from homoveratrylamine via amidation, Bischler-Napieralski reaction and the subsequent reduction. The enantiomerically pure tetrahydroisoquinolines (S)- (-)-norcryptostyline I [(S)-(-)-1], (S)-(-)-norcryptostyline II [(S)-(-)-2], (R)-(+)-salsolidine [(R)-(+)-3] and (S)-(-)-norlaudanosine [(S)-(-)-4] were then obtained in 45%, 40%, 41% and 38% yields, respectively, via resolution of the racemic compounds (RS)-(±)-1-4 with half equivalent of chiral acids. In addition, the enantiomerically enriched compounds (R)-(+)-1, (R)-(+)-2, (S)-(-)-3 and (R)-(+)-4 from the mother liquors were efficiently racemized via a one-pot redox method in almost quantitative yields.
- Zhu, Ruiheng,Xu, Zhangli,Ding, Wei,Liu, Shiling,Shi, Xiaoxin,Lu, Xia
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- Asymmetric Transfer Hydrogenation of Unhindered and Non-Electron-Rich 1-Aryl Dihydroisoquinolines with High Enantioselectivity
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The use of arene/Ru/TsDPEN catalysts bearing a heterocyclic group on the TsDPEN in the asymmetric transfer hydrogenation (ATH) of dihydroisoquinolines (DHIQs) containing meta- or para-substituted aromatic groups at the 1-position results in the formation of products of high enantiomeric excess. Previously, only 1-(ortho-substituted)aryl DHIQs, or with an electron-rich fused ring gave products with high enantioselectivity; therefore, this approach solves a long-standing challenge for imine ATH.
- Barrios-Rivera, Jonathan,Xu, Yingjian,Wills, Martin
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supporting information
p. 6283 - 6287
(2020/09/02)
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- Josiphos-Type Binaphane Ligands for Iridium-Catalyzed Enantioselective Hydrogenation of 1-Aryl-Substituted Dihydroisoquinolines
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Convenient synthesis and useful application of a series of Josiphos-type binaphane ligands were described. The iridium complexes of these chiral diphosphines displayed excellent enantioselectivity and good reactivity in the asymmetric hydrogenation of challenging 1-aryl-substituted dihydroisoquinoline substrates (full conversions, up to >99% ee, 4000 TON). The use of 40% HBr (aqueous solution) as an additive dramatically improved the asymmetric induction of these catalysts. This transformation provided a highly efficient and enantioselective access to chiral 1-aryl-substituted tetrahydroisoquinolines, which were of great importance and common in natural products and biologically active molecules.
- Nie, Huifang,Zhu, Yupu,Hu, Xiaomu,Wei, Zhao,Yao, Lin,Zhou, Gang,Wang, Pingan,Jiang, Ru,Zhang, Shengyong
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supporting information
p. 8641 - 8645
(2019/10/17)
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- Enantioselective Synthesis of 1-Aryl-Substituted Tetrahydroisoquinolines Through Ru-Catalyzed Asymmetric Transfer Hydrogenation
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A convenient and general asymmetric transfer hydrogenation of a wide array of 1-aryl-3,4-dihydroisoquinoline derivatives using a [RuIICl(η6-benzene)TsDPEN] complex in combination with a 5:2 HCOOH-Et3N azeotropic mixture as a hydrogen source was developed. Under mild reaction conditions, the described catalytic transformation secured a practical synthetic access to the corresponding valuable chiral 1-aryltetrahydroisoquinoline units with high atom economy, a broad substrate scope, high isolated yields (up to 97%) and good to excellent enantioselectivities (up to 99% ee). It was found that the stereochemical outcome of the reaction was strongly influenced by both the structure of the catalyst and the substituents present on the substrate. The synthetic utility of the present protocol has been demonstrated through the asymmetric synthesis of several biologically important alkaloids including the antiepileptic drug agent 1c, as well as (-)-nor-cryptostyline alkaloids I and II.
- Perez, Marc,Wu, Zi,Scalone, Michelangelo,Ayad, Tahar,Ratovelomanana-Vidal, Virginie
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p. 6503 - 6514
(2015/10/19)
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- Mild rhodium(III)-catalyzed cyclization of amides with α,β- unsaturated aldehydes and ketones to azepinones: Application to the synthesis of the homoprotoberberine framework
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Seven! The title reaction can be described as an intermolecular annulation involving tandem C-H activation, cyclization to give the seven-membered ring, and condensation steps. Biologically interesting azepinone derivatives can be prepared in this way. Th
- Shi, Zhuangzhi,Grohmann, Christoph,Glorius, Frank
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p. 5393 - 5397
(2013/06/05)
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- Restraining the flexibility of the central linker in terameprocol results in constrained analogs with improved growth inhibitory activity
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The semi-synthetic lignan terameprocol inhibits the transcription of several inflammatory and oncogenic genes and has been evaluated for its anti-cancer properties. Here we investigated the effect of restricting the flexibility of the carbon linker connecting the terminal rings of terameprocol on its growth inhibitory activity. Conformational restriction was explored by introducing unsaturation, inserting polar entities with limited flexibility and cyclization of the connecting linker. Twenty three compounds were synthesized and evaluated on a panel of malignant human cells. The most promising compounds were those with non-polar linkers, as seen in butadiene 1a and the cyclized benzylideneindane analog 7. Both compounds were more potent than terameprocol on pancreatic BxPC-3 cells with GI50 values of 3.4 and 8.1 μM, respectively. Selected isomers of 1a (E,E) and 7 (Z) adopted low energy bent conformations that mimicked the low energy conformer of terameprocol. It is tempting to propose that conformational similarity to terameprocol may have contributed to their good activity. The scaffolds of 1a and 7 should be further investigated for their anticancer potential.
- Ho, Sherman Si Han,Go, Mei Lin
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supporting information
p. 6127 - 6133
(2013/11/06)
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- Synthesis of isoquinoline alkaloids via oxidative amidation-bischler- napieralski reaction
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A straightforward synthesis of -keto amides by coupling primary amines with aryl dibromoethanones under oxidative amidation conditions has been developed. The -keto amides were then subjected to heterocyclodehydration reaction under Bischler-Napieralski conditions followed by aromatization with DBU provided 1-benzoyl isoquinolines in a two-stage process. Utilizing this methodology, isoquinoline alkaloids such as thalmicrinone, papavaraldine, and pulcheotine A were synthesized in excellent yields. Georg Thieme Verlag Stuttgart · New York.
- Shankar,More, Satish S.,Madhubabu,Vembu,Syam Kumar
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supporting information; experimental part
p. 1013 - 1020
(2012/06/01)
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- A highly efficient and enantioselective access to tetrahydroisoquinoline alkaloids: Asymmetric hydrogenation with an iridium catalyst
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Efficient and enantioselective: Using the iodine-bridged dimeric iridium complex [{Ir(H)[(S,S)-(f)-binaphane]}2(μ-I)3] +I- (1) a wide range of tetrahydroisoquinoline alkaloids, including the substructure of the pharmaceutical drug solifenacin, were obtained with excellent enantioselectivities and high turnover numbers (see scheme). Copyright
- Chang, Mingxin,Li, Wei,Zhang, Xumu
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supporting information; experimental part
p. 10679 - 10681
(2011/12/05)
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- Ruthenium dioxide in fluoro acid medium. III. Aplication to the synthesis of aporphinic, homoaporphinic and dibenzazocinic alkaloids. Studies towards the preparation of azafluoranthenic skeleton
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Intramolecular oxidative couplings of phenylalkyltetrahydroisoquinoline precursors in aporphinic and homoaporphinic alkaloids by using RuO2,2H2O in fluoro acidic media were performed. A comparative study of our reagent with TTFA has been made with different precursors. The procedure was also extended to the synthesis of one dibenzazocinic alkaloid. Then, we attempted to synthetize the azafluoranthenic ring, using phenolic and non phenolic isoquinoline precursors.
- Landais,Robin
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p. 7185 - 7196
(2007/10/02)
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