- Decarboxylative Conjunctive Cross-coupling of Vinyl Boronic Esters using Metallaphotoredox Catalysis
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The synthesis of complex alkyl boronic esters through conjunctive cross-coupling of vinyl boronic esters with carboxylic acids and aryl iodides is described. The reaction proceeds under mild metallaphotoredox conditions and involves an unprecedented decarboxylative radical addition/cross-coupling cascade of vinyl boronic esters. Excellent functional-group tolerance is displayed, and application of a range of carboxylic acids, including secondary α-amino acids, and aryl iodides provides efficient access to highly functionalized alkyl boronic esters. The decarboxylative conjunctive cross-coupling was also applied to the synthesis of sedum alkaloids.
- Aggarwal, Varinder K.,Duong, Vincent K.,Mega, Riccardo S.,Noble, Adam
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p. 4375 - 4379
(2020/02/11)
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- Synthesis of β-Amino Ketones by Addition of Aryl Methyl Ketones to Sulfinimines: Application to the Total Synthesis of HPA-12, Norsedamine, and Sedamine
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Synthesis of β-sulfinamido ketones was accomplished by the addition of silyl enol ethers derived from arylmethyl ketones to chiral sulfinimines in excellent yield and selectivity. Application of the formed β-amino substituted ketones is exemplified in the total synthesis of sphingolipid HPA-12 and the sedamine alkaloids.
- Reddy, Arava Amaranadha,Prasad, Kavirayani R.
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p. 13488 - 13499
(2017/12/26)
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- A rapid access to (±)-sedamine and some original N -benzyl unsaturated analogues
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Reduction of N-alkyl-2-(2-hydroxy-2-phenylethyl)pyridinium salts using excess of sodium triacetoxyborohydride afforded exclusively the corresponding tetrahydropyridine derivative bearing a piperidine ring with a double bond in the 3,4-position. Furthermore, under these conditions, syn-1,3-amino alcohols were obtained in good yield and diastereoselectivity. Georg Thieme Verlag Stuttgart · New York.
- Boussonniere, Anne,Ranaivondrambola, Tsiresy,Lebreton, Jacques,Mathe-Allainmat, Monique
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experimental part
p. 2456 - 2462
(2010/09/04)
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- Studies on the Eschenmoser coupling reaction and insights on its mechanism. Application in the synthesis of Norallosedamine and other alkaloids
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The conditions of the Eschenmoser coupling reaction were studied. The formation of the α-thioiminium ion was achieved faster in the presence of an additive (NaI) and dry chloroform as the preferred solvent. The developed conditions were used for the second part of the reaction (the sulfur extrusion itself). The present protocol avoids the formation of byproducts, which were previously described as a major drawback to be overcome. Electrospray ionization tandem mass spectrometry was used to characterize some aspects (intermediates) of the first step of the reaction mechanism. Some reduction conditions were properly tested and the selected conditions were applied to the synthesis of the natural alkaloid Norallosedamine and other derivatives.
- Neto, Brenno A.D.,Lapis, Alexandre A.M.,Bernd, Alinne B.,Russowsky, Dennis
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experimental part
p. 2484 - 2496
(2009/08/07)
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- Asymmetric synthesis of Sedum alkaloids via lithium amide conjugate addition
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Conjugate addition of lithium (R)-N-allyl-N-(α-methylbenzyl)amide or lithium (R)-N-but-3-enyl-N-(α-methylbenzyl)amide to an alkyl hexa-2,4-dienoate or alkyl hepta-2,6-dienoate, followed by ring-closing metathesis of the olefin functionalities within the resultant β-amino ester, generates a range of diastereoisomerically pure azacycles in good yield. These homochiral templates are readily transformed to a range of piperidine alkaloids of the Sedum family, and the corresponding five-, seven- and eight-membered ring homologues.
- Davies, Stephen G.,Fletcher, Ai M.,Roberts, Paul M.,Smith, Andrew D.
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experimental part
p. 10192 - 10213
(2010/02/28)
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- Asymmetric synthesis of pyrido[1,2-c]pyrimidinones
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"Asymmetric Electrophilic α-Amidoalkylation" reactions with a chiral alkylaminocarbonyl unit as chiral auxiliary are used for the stereoselective synthesis of 2-substituted piperidine derivatives. Intramolecular condensation of the nitrogen of the aminoca
- Pabela, J?rg,Wadenstorferb, Elmar,Wannera, Klaus T.
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experimental part
p. 653 - 661
(2009/12/26)
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- An efficient approach to 2-substituted N-tosylpiperdines: asymmetric synthesis of 2-(2-hydroxy substituted)piperidine alkaloids
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We have developed an efficient and a general approach to chiral 2-substituted N-tosylpiperidines starting from chiral α-substituted-N-tosylaziridines. Using this approach, we have synthesized (+)-coniine. The synthesis of chiral N-tosyl-2-piperidinylethanol 15 and ent-15, was achieved from l- and d-aspartic acids, respectively in few steps. Piperidine 15 was converted into 2-(2-hydroxysubstituted)piperidines of type 2 in optically active form. By applying this strategy, asymmetric syntheses of halosaline (R,R)-2a, (+)- and (-)-sedamine 2b, (+)- and (-)-allosedamine 2c, (+)- and (-)-sedridine 2d, (+)- and (-)-allosedridine 2e, (+)-tetraponerine T-3 3a, T-4 3c, T-7 3b, and T-8 3d have been achieved in high yields. These stereoisomers can be interconverted via Mitsunobu inversion in excellent yields.
- Bisai, Alakesh,Singh, Vinod K.
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p. 1907 - 1910
(2007/10/03)
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- Synthesis of sedamine by tethered cyclofunctionalisation
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The piperidine alkaloid, (+)-sedamine has been synthesised starting from (S)-1-phenyl-3-butenol using a stereoselective, intramolecular palladium-catalysed cyclocarbonylation reaction of a substituted hydroxylamine.
- Bates, Roderick W.,Boonsombat, Jutatip
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p. 520 - 523
(2007/10/03)
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- Diastereoselective, one-pot synthesis of γ-amino alcohols from ketimines
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Deprotonation of ketimines with lithium diisopropyl amide, followed by reaction with aldehydes and subsequent reduction with aluminium hydrides gave γ-amino alcohols with moderate to good syn selectivity. The scope and limitations of this preparative meth
- Veenstra,Kinderman
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p. 1109 - 1112
(2007/10/03)
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- A concise synthesis of homochiral sedamines and related alkaloids. A new reductive application of Jacobsen's catalyst
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Two methods for the generation of both enantiomers of sedamine [1- methyl-2-(2-phenyl-2-hydroxy-1-ethyl)piperidine] in high optical purity have been elaborated. The first utilises the lipase-mediated kinetic resolution of racemic acetates and the second involves the NaBH4 mediated reduction of ketones catalysed by Jacobsen's catalyst. Some related applications of these reactions are also disclosed.
- Yu, Chu-Yi,Meth-Cohn, Otto
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p. 6665 - 6668
(2007/10/03)
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- Trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed amidoalkylation of silylenolethers. Stereocontrolled syntheses of (+/-)-sedamine and (+/-)-norsedamine
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Trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed addition of 1-trimethylsilyloxy-1-phenylethene to N-ethoxycarbonyl- and N-tert-butoxycarbonyl-2-ethoxypiperidines (3a and 3b, respectively) afforded the corresponding ketocarbamates 4a and 4b, in excellent yields. Stereoselective conversion to (±)-norsedamine (7) and (±)-sedamine (8) is described.
- Pilli,Dias
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p. 2213 - 2229
(2007/10/02)
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- Nitrone Cycloadditions: Synthesis of (+/-)-Andrachamine
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The usefulness of the cycloaddition of alkenes to 2-alkyl-2,3,4,5-tetrahydropyridine oxides for the preparation of trans-2,6-dialkylpiperidines is confirmed by a stereoselective synthesis of (+/-)-andrachamine.Peroxy acid oxidation of 9-oxa-1-azabicyclononanes does not lead regioselectively to the corresponding 2-alkyl-2,3,4,5-tetrahydropyridine oxide, as had previously been claimed.
- Carruthers, William,Coggins, Peter,Weston, John B.
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p. 2323 - 2327
(2007/10/02)
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- ASYMMETRIC ELECTROPHILIC α-AMIDOALKYLATION 5: IMPROVED STEREOSELECTIVITIES THROUGH NEW CHIRAL AUXILIARIES
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Enamides of type 2 were employed in asymmetric α-amidoalkylation reactions with silyl enol ether 4 as nucleophile.Depending on the chiral auxiliary used, (R)-5/(S)-5 stereoselectivities up to 95/5 could be reached.Based on the obtained results a model for
- Wanner, Klaus Th.,Kaertner, Annerose,Wadenstorfer, Elmar
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p. 2549 - 2556
(2007/10/02)
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- ASYMMETRIC α-AMIDOALKYLATION. SYNTHESIS OF α-SUBSTITUTED PIPERIDINES OF HIGH ENANTIOMERIC PURITY
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A stereoselective α-amidoalkylation was performed employing the chiral and cyclic enamide 1.The resulting amides 6 were employed in the synthesis of the title products.
- Wanner, Klaus Th.,Kaertner, Annerose
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p. 921 - 924
(2007/10/02)
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- Asymmetric α-Amidoalkylation. Syntheses of Enantiomerically Pure α-Substituted Piperidines with 1-Camphanoyl-1,2,3,4-tetrahydropyridine
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In a novel asymmetric synthesis the homochiral enamide 1 is coupled with the silyl enol ethers 5a-c in a diastereoselective fashion to afford the amidoalkylation products 6/7a-c.These are employed in the synthesis of enantiomerically pure, in α-position R
- Wanner, Klaus Th.,Kaertner, Annerose
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p. 1253 - 1267
(2007/10/02)
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