- Strategies for the Asymmetric Construction of Pelletierine and its Use in the Synthesis of Sedridine, Myrtine, and Lasubine
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Three methods for the asymmetric synthesis of both enantiomers of pelletierine 6 are reported. Bella's proline-based Mannich process gave (R)- and (S)-Cbz-protected 6 in good yields from Δ1-piperideine 14 and in reasonable enantiomeric excess (74–80 % ee). An intramolecular aza-Michael, cinchona-based, organocatalytic method is also reported. With commercially available 9-amino quinine (24a) and quinidine (24b) catalysts, Cbz-protected α,β-unsaturated ketone 23 also gave (R)- and (S)-Cbz-protected 6 in good yields and enantiomeric excess (90–99 % ee). This material was used to synthesize both optically active forms of deoxyhalofuginone (26), an analogue of febrifugine which is of interest as an anti-fibrotic agent. Finally, a resolution of racemic pelletierine using (R)- and (S)-mandelic acid 27 is reported. This scalable method gave both enantiomers of Cbz- and Boc-protected 6 in excellent enantiomeric excess (≥ 99 %). Both highly enantioenriched forms of 6 (obtained from the resolution study) were used to synthesize several alkaloids. Firstly, (–)-(S)-Cbz-protected pelletierine 17 was used to prepare naturally occurring sedridine (32) and its epimer allosedridine (8). Then the preparation of both enantiomers of the quinolizidine myrtine (33) by an olefination-intramolecular aza-Michael sequence is reported. Finally, the synthesis of the epimeric quinolizidine alkaloids, lasubine I (34) and lasubine II (35), from (+)- and (–)-Boc-protected pelletierine (29) respectively, is discussed.
- Zaidan, Raed K.,Evans, Paul
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p. 5354 - 5367
(2019/06/25)
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- Henry-Nef reaction: A practical and versatile chiral pool route to 2-substituted pyrrolidine and piperidine alkaloids
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The paper describes the synergistic protocol developed by combinatorial Henry and Nef reaction for the synthesis of 2-substituted pyrrolidine and piperidine alkaloids containing 1,3-aminoketone and 1,3-amino alcohol units. The utility of the protocol is demonstrated by asymmetric synthesis of 12 natural products of which asymmetric synthesis of (-)-N-methylpelletierine is presented for the first time. The one-carbon homologation described also provides an alternate route for the synthesis of key intermediates homoprolinol and homopipecolinol used as synthetic precursors for several alkaloids and construction of β-amino acids from α-amino acids.
- Bhat, Chinmay,Tilve, Santosh G.
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p. 6129 - 6143
(2013/07/27)
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- Enantioselective approach to quinolizidines: Total synthesis of cermizine D and formal syntheses of senepodine G and cermizine C
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The formal syntheses of C5-epi-senepodine G and C 5-epi-cermizine C have been accomplished through a novel diastereoselective, intramolecular amide Michael addition process. The total synthesis of cermizine D has been achieved throug
- Veerasamy, Nagarathanam,Carlson, Erik C.,Collett, Nathan D.,Saha, Mrinmoy,Carter, Rich G.
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p. 4779 - 4800
(2013/06/27)
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- Asymmetric synthesis of (+)-vertine and (+)-lythrine
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The total syntheses of the Lythracea alkaloids (+)-vertine and (+)-lythrine are described. Enantioenriched pelletierine is used as a chiral building block and engaged into a two step pelletierine condensation leading to two quinolizidin-2-one diastereomers in a 8:1 ratio. The major product is used in the synthesis of (+)-vertine via aryl-aryl coupling and ring closing metathesis to provide a Z-alkene α to the lactone carbonyl function. The same procedure was used for (+)-lythrine after base induced epimerization of the main quinolizidin-2-one diastereomer. Alternative classical ring closure strategies like macrolactonisation or aryl-aryl coupling failed.
- Chausset-Boissarie, La?titia,àrvai, Roman,Cumming, Graham R.,Guénée, Laure,Kündig, E. Peter
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p. 6473 - 6479
(2012/09/08)
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- Biomimetic organocatalytic asymmetric synthesis of 2-substituted piperidine-type alkaloids and their analogues
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Natural substances such as pelletierine and its analogues have been prepared in up to 97% ee and good yield by a protective-group-free, biomimetic approach. Usage of benzonitrile or acetonitrile as solvents effectively prevents product racemization.
- Monaco, Mattia R.,Renzi, Polyssena,Scarpino Schietroma, Daniele M.,Bella, Marco
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supporting information; experimental part
p. 4546 - 4549
(2011/10/31)
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- Regioselective and stereoselective copper(I)-Promoted allylation and conjugate addition of N -Boc-2-lithiopyrrolidine and N -Boc-2-lithiopiperidine
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Copper salts have been screened for transmetalation and electrophilic quench of N-tert-butoxycarbonyl-2-lithiopyrrolidine (N-Boc-2-lithiopyrrolidine) and N-Boc-2-lithiopiperidine, formed by deprotonation of N-Boc-pyrrolidine and N-Boc-piperidine, respectively. Transmetalation with zinc chloride then (lithium chloride solubilized) copper cyanide followed by allylation typically gives mixtures of regioisomers (SN2 and SN2′ products), whereas transmetalation with copper iodideTMEDA then allylation occurs regioselectively (SN2 mechanism). Addition to an enone or α,β-unsaturated ester occurs by 1,4-addition. Asymmetric deprotonation of N-Boc-pyrrolidine or dynamic resolution in the presence of a chiral ligand of N-Boc-2-lithiopiperidine followed by the zinc/copper chemistry was successful and gave the allylated pyrrolidine and piperidine products with good enantioselectivity, although use of the copper iodide chemistry resulted in some loss of enantiopurity. The chemistry provides formal syntheses of (+)-allosedridine, (+)-lasubine II, and (+)-pseudohygroline and has been used for the synthesis of (+)-coniine, (-)-pelletierine, (+)-coniceine, (-)-norhygrine, and the ant extract alkaloids cis- and trans-2-butyl-5- propylpyrrolidine.
- Coldham, Iain,Leonori, Daniele
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experimental part
p. 4069 - 4077
(2010/08/20)
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- Preparation of enantiopure substituted piperidines containing 2-alkene or 2-alkyne Chains: Application to total syntheses of natural quinolizidine- alkaloids
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"Chemical Equation Presented" A general method, for the preparation of enantiopure 2-alkene- or 2-alkyne-containing chain substituted piperidines was established by using nonracemic Betti base as a chiral auxiliary. The key step is that the auxiliary residue was removed by a novel base-catalyzed N-debenzylation via a formation of o-quinone methide mechanism in stead, of the traditional hydrogenolysis, by which the alkene or alkyne groups survived. By this method, ten 2-alkene- or 2-alkyne-containing chain substituted piperidines were prepared on the gram scale within a few hours. To demonstrate the efficiency of the method and the versatility of the product, total, syntheses of natural alkaloids (+)-pelletierine((-)-lasubine II, and (-)-cermizine C were achieved by using (S)-2-allyl-N-Bocpiperidine as a versatile building block.
- Cheng, Guolin,Wang, Xinyan,Su, Deyong,Liu, Hui,Liu, Fei,Hu, Yuefei
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supporting information; experimental part
p. 1911 - 1916
(2010/06/15)
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- Highly enantioselective catalytic dynamic resolution of N-boc-2-lithiopiperidine: Synthesis of (R)-(+)- N-boc-pipecolic acid, (S)-(-)-coniine, (S)-(+)-pelletierine, (+)-β-conhydrine, and (S)-(-)-ropivacaine and formal synthesis of (-)-lasubine II and (+)-cermizine C
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The catalytic dynamic resolution (CDR) of rac-2-lithio-N-Boc-piperidine using chiral ligand 8 or its diastereomer 9 in the presence of TMEDA has led to the highly enantioselective syntheses of both enantiomers of 2-substituted piperidines using a wide range of electrophiles. The CDR has been applied to the synthesis of (R)- and (S)-pipecolic acid derivatives, (+)-β-conhydrine, (S)-(+)-pelletierine, and (S)-(-)-ropivacaine and the formal synthesis of ()-lasubine II and (+)-cermizine C.
- Beng, Timothy K.,Gawley, Robert E.
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supporting information; experimental part
p. 12216 - 12217
(2010/12/25)
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