- Stereodivergent Synthesis of 1-Hydroxymethylpyrrolizidine Alkaloids
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A first stereodivergent strategy for the asymmetric synthesis of all stereoisomers of 1-hydroxymethylpyrrolizidine alkaloids is developed using an asymmetric self-Mannich reaction as a key step. An anti-selective self-Mannich reaction of methyl 4-oxobutanoate with the PMP-amine catalyzed by a chiral secondary amine is successfully optimized for the asymmetric synthesis of (+)-isoretronecanol and (-)-isoretronecanol. A syn-selective self-Mannich reaction catalyzed by proline is utilized for the asymmetric synthesis of the diastereomer, (+)-laburnine, and its enantiomer, (-)-trachelanthamidine.
- Appayee, Chandrakumar,Sarkale, Abhijeet M.
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- Pyrrolizidines, indolizidines and quinolizidines via a double reductive cyclisation protocol: concise asymmetric syntheses of (+)-trachelanthamidine, (+)-tashiromine and (+)-epilupinine
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The asymmetric syntheses of pyrrolizidine, indolizidine and quinolizidine alkaloids have been achieved using the diastereoselective conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to α-alkenyl-α,β-unsaturated esters followed by diastereoselective protonation of the resultant enolates as the key stereodefining steps. The azabicyclic scaffolds were then efficiently constructed upon sequential oxidative cleavage of the olefinic units within the resultant β-amino esters and hydrogenolytic N-debenzylation of the corresponding dialdehydes, which occurs with concomitant double reductive cyclisation. Subsequent reduction of the ester moieties with LiAlH4gave (+)-trachelanthamidine, (+)-tashiromine, (1S,8aR)-1-(hydroxymethyl)octahydroindolizine and (+)-epilupinine in 4.9, 4.1, 3.0 and 5.9% overall yield, respectively, in only six steps from commercially available starting materials.
- Brambilla, Marta,Davies, Stephen G.,Fletcher, Ai M.,Roberts, Paul M.,Thomson, James E.,Zimmer, David
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p. 7417 - 7429
(2016/11/11)
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- Organocatalytic asymmetric mannich cyclization of hydroxylactams with acetals: Total syntheses of ( )-epilupinine, ( )-tashiromine, and ( )-trachelanthamidine
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An asymmetric, organocatalytic, one-pot Mannich cyclization between a hydroxylactam and acetal is described to provide fused, bicyclic alkaloids bearing a bridgehead N atom. Both aliphatic and aromatic substrates were used in this transformation to furnish chiral pyrrolizidinone, indolizidinone, and quinolizidinone derivatives in up to 89% yield and 97% ee. The total syntheses of (-)-epilupinine, (-)-tashiromine, and (-)-trachelanthamidine also achieved to demonstrate the generality of the process.
- Koley, Dipankar,Krishna, Yarkali,Srinivas, Kyatham,Khan, Afsar Ali,Kant, Ruchir
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p. 13196 - 13200
(2015/02/19)
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- Pyrrolizidine esters and amides as 5-HT4 receptor agonists and antagonists
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A series of pyrrolizidine esters, amides, and ureas was prepared and tested for 5-HT4 and 5-HT3 receptor binding, 5-HT4 receptor agonism in the rat tunica muscularis mucosae (TMM) assay, and for 5-HT3 receptor-mediated functional antagonism in the Bezold-Jarisch reflex assay. Several pyrrolizidine derivatives were identified with high affinity for the 5-HT4 receptor, including benzamide 12a (SC-53116), a potent and selective 5-HT4 partial agonist that exhibits efficacy in promoting antral contractions and activity in promoting gastric emptying in canine models. Also discovered were 5-HT4 receptor antagonists, including imidazopyridine amide 12h (SC-53606), which is a potent and selective 5-HT4 receptor antagonist with a pA2 value of 8.13 in the rat TMM assay. N-Methyl indole ester 13d was identified as a potent 5-HT 4 antagonist with a pA2 value of 8.93. High selectivity was observed for these pyrrolizidine derivatives versus other monoamine receptors, including 5-HT1, 5-HT2, D1, D 2, α1, α2, and β receptors. 2006 American Chemical Society.
- Becker, Daniel P.,Flynn, Daniel L.,Moormann, Alan E.,Nosal, Roger,Villamil, Clara I.,Loeffler, Richard,Gullikson, Gary W.,Moummi, Chafiq,Yang, Dai-C.
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p. 1125 - 1139
(2007/10/03)
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- Highly efficient and stereoselective radical addition of tertiary amines to electron-deficient alkenes - Application to the enantioselective synthesis of necine bases
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A convenient and highly efficient method for the regio- and stereoselective addition of tertiary amines to electron-deficient alkenes has been elaborated. It is based on a radical chain reaction of α-aminyl radicals with alkenes, induced by a photoelectro
- Bertrand, Samuel,Hoffmann, Norbert,Pete, Jean-Pierre
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p. 2227 - 2238
(2007/10/03)
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- Neo Coramandaline, a Pyrrolizidine Alkaloid from Cynoglossum furcatum
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The pyrrolizidine alkaloids of Cynoglossum furcatum have been isolated and characterised. They are neo coramandaline 1, a new pyrrolizidine ester alkaloid and echinatine 3. Neo coramandaline is formulated as 9-O-(-)viridifloryl laburnine on the basis of spectroscopic measurements and hydrolysis.
- Ravi, S.,Lakshmanan, A. J.
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- Stereoselective radical addition of tertiary amines to (5R)-5- menthyloxy-2[5H]-furanone: Application to the enantioselective synthesis of (-)-isoretronecanol and (+)-labumine
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The adducts of a stereoselective radical addition of tertiary amines with (5R)-5-menthyloxy-2[5H]-furanone were transformed very efficiently into enantiomerically pure pyrrolizidine and indolizidine alkaloids, through a three steps sequence.
- Bertrand, Samuel,Hoffmann, Norbert,Pete, Jean-Pierre
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p. 3173 - 3174
(2007/10/03)
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- Enamino ester reduction: A short enantioselective route to pyrrolizidine and indolizidine alkaloids. Synthesis of (+)-laburnine, (+)-tashiromine, and (-)-isoretronecanol
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Various chiral pyrrolidine tetrasubstituted β-enamino esters were reduced catalytically or chemically with good to moderate diastereoselectivity owing to a chiral induction originated from (S)-α- methylbenzylamine. With endocyclic double bond compounds, t
- David, Olivier,Blot, Jerome,Bellec, Christian,Fargeau-Bellassoued, Marie-Claude,Haviari, Gjergj,Celerier, Jean-Pierre,Lhommet, Gerard,Gramain, Jean-Claude,Gardette, Daniel
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p. 3122 - 3131
(2007/10/03)
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- An enantio- and diastereoselective synthesis of (-)-isoretronecanol and (+)-trachelanthamidine from a meso precursor
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Two diastereomeric pyrrolizidine alkaloids, (-)-isoretronecanol and (+)- trachelanthamidine, have been synthesized in an enantio- and diastereoselective manner starting from a meso precursor via a catalytic asymmetrization.
- Konno, Hiroyuki,Kishi, Masayo,Hiroya, Kou,Ogasawara, Kunio
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- Enantioselective Synthesis of (+)-Indolizidine, (+)-Laburnine and (+)-Elaeokanines A and C using the Diels-Alder Reaction of α-(2-eyo-Hydroxy-10-bornylsulfinyl)maleimide
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The Diels-Alder adduct 5 derived from the N-butynylmaleimide 6 and cyclopentadiene has been transformed into the tetracyclic lactams 12 and 19 via a common precursor 9.The lactams 12 and 19 have been converted into (+)-indolizidine 1 and (+)-laburnine 2, respectively, via retro-Diels-Alder reaction.Similar methodology has bee succesfully applied to the synthesis of (+)-elaeokanine A 3 and (+)-elaeokanine C 4.
- Arai, Yoshitsugu,Kontani, Tohru,Koizumi, Toru
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- A Novel Approach to Bicyclic Alkaloids Using a Tandem Diastereoselective Acyliminocyclization and Retro Diels-Alder Reaction Sequence. Synthesis of (+)-Indolizidine and (+)-Laburnine
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A new aproach to diastereoselective cationic cyclization by stereocontrol due to the bicycloheptene moiety in a chiral γ-hydroxy lactam is described.The diastereoselective reaction followed by Diels-Alder cycloreversion has ben succesfully applied to a chiral synthesis of (+)-indolizidine and (+)-laburnine (=trachelanthamidine).
- Arai, Yoshitsugu,Kontani, Tohru,Koizumi, Toru
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p. 2135 - 2138
(2007/10/02)
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- MINOR ALKALOIDS OF HELIOTROPIUM CURASSAVICUM
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Isolation and structure determination of the minor alkaloids of Heliotropium curassavicum are described.These include the new pyrrolizidine alkaloids, heliocurassavine , heliocoromandaline , heliocurassavicine , heliocurassavinine , curassavinine , coromandalinine , heliovinine and curassanecine .Structures were established by high resolution 1H NMR, mass spectrometry and paper electrophoresis of the alkaloids and their hydrolysis products. - Key Word Index-Pyrrolizidine alkaloids; heliocurassavine; heliocurassavinine; heliocurassavicine; heliocoromadaline; curassavinine; coromandalinine; heliovinine; curassanecine.
- Mohanraj, Subramaniam,Subramanian, Polur S.,Herz, Werner
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p. 1775 - 1780
(2007/10/02)
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- Synthesis of Optically Active Pyrrolizidine Bases
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Regiospecific 1,3-dipolar cycloaddition of ethyl propiolate to the NO-diformyl derivative (1) of natural (-)-4-hydroxy-L-proline followed by stereospecific hydrogenation gave ethyl (+)-6α-hydroxy-β-pyrrolizidine-1α-carboxylate (4).Confirmation of the abso
- Robins, David J.,Sakdarat, Santi
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p. 909 - 913
(2007/10/02)
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