- Stereoselective total synthesis of the piperidine alkaloids, (+)-coniine, (+)-pseudoconhydrine, and (+)-sedamine through a common intermediate
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The stereoselective total synthesis of the piperidine alkaloids, (+)-coniine, (+)-pseudoconhydrine and (+)-sedamine has been achieved through a common intermediate generated from butane-1,4-diol. The synthetic sequence involves a Maruoka asymmetric allylation and ring-closing metathesis as the key steps.
- Satyalakshmi, Gandham,Suneel, Kanaparthy,Shinde, Digambar Balaji,Das, Biswanath
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Read Online
- Enantioselective Rhodium-Catalyzed Allylation of Aliphatic Imines: Synthesis of Chiral C Aliphatic Homoallylic Amines
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Reported herein is a method for the efficient syntheses of optically active 1-alkyl homoallylic amines in yields up to 95%, 13.5:1 dr, and 98% ee under mild, aqueous reaction conditions, via the Rh-catalyzed asymmetric allylation of aliphatic aldimines. This method provides a streamlined synthetic platform for the preparation of indolizidine and piperidine alkaloids, thus demonstrating its usefulness.
- Li, Wei-Sian,Kuo, Ting-Shen,Hsieh, Meng-Chi,Tsai, Ming-Kang,Wu, Ping-Yu,Wu, Hsyueh-Liang
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p. 5675 - 5679
(2020/08/10)
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- Rhodium-Catalyzed Asymmetric Intramolecular Hydroamination of Allenes
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The rhodium-catalyzed asymmetric intramolecular hydroamination of sulfonyl amides with terminal allenes is reported. It provides selective access to 5- and 6-membered N-heterocycles, scaffolds found in a large range of different bioactive compounds. Moreover, gram scale reactions, as well as the application of suitable product transformations to natural products and key intermediates thereof are demonstrated.
- Berthold, Dino,Geissler, Arne G. A.,Giofré, Sabrina,Breit, Bernhard
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supporting information
p. 9994 - 9997
(2019/07/04)
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- Regio- and Stereoselective Alkylation of Pyridine-N-oxides: Synthesis of Substituted Piperidines and Pyridines
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Regio- and stereoselective addition of alkyl Grignard reagents to pyridine-N-oxides gave C2-alkylated N-hydroxy-1,2,5,6-tetrahydropyridines and trans-2,3-disubstituted N-hydroxy-1,2,5,6-tetrahydropyridines in good to excellent yields. These intermediates were aromatized or alternatively reduced in one-pot methodologies for efficient syntheses of alkylpyridines or piperidines, respectively. These reactions have a broad substrate scope and short reaction times.
- Barange, Deepak Kumar,Johnson, Magnus T.,Cairns, Andrew G.,Olsson, Roger,Almqvist, Fredrik
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supporting information
p. 6228 - 6231
(2016/12/23)
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- A direct and general method for the reductive alkylation of tertiary lactams/amides: Application to the step economical synthesis of alkaloid (-)-morusimic acid D
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Full details of the direct and general method for the reductive alkylation of tertiary lactams and amides to give tertiary sec-alkylamines are presented. This one-pot method consists of in situ activation of a lactam or an amide with Tf2O/DTBMP, addition of a Grignard reagent, and reduction of the resulting iminium intermediates. Alkyl, benzyl, and aryl Grignard reagents and several reductants or reducing conditions (LiAlH4, NaBH4, Hantzsch ester, Bu3SnH, Pd(OH)2/C, H2) could be used effectively. Reductive alkylations of substituted lactams demonstrated good to excellent 1,3-asymmetric induction to provide the corresponding di- or trisubstituted pyrrolidine/piperidine in 6:1 (LiAlH4), 11:1 (Et 3SiH), and 20:1 (catalytic hydrogenation) cis/trans diastereoselectivity, respectively. The versatility of this methodology was demonstrated by its application in the concise stereoselective synthesis of piperidine alkaloid (-)-morusimic acid.
- Xiao, Kai-Jiong,Wang, Yu,Huang, Ying-Hong,Wang, Xiao-Gang,Huang, Pei-Qiang
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p. 8305 - 8311
(2013/09/24)
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- Synthesis of optically active heterocyclic compounds via deracemization of 1,2-diol monotosylate derivatives bearing a long aliphatic chain by a combination of enzymatic hydrolysis with Mitsunobu inversion
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We have succeeded in accomplishing the deracemization of (±)-2-acetoxydecyl and (±)-acetoxy-6-benzyloxyhexyl tosylates, which have a long substituent, via an enzyme-mediated enantioselective hydrolysis with a Mitsunobu inversion using polymer-supported triphenylphosphine to afford the corresponding (S)-enantiomer. Enantiomerically pure (S)- and (R)-γ-dodecalactones, a fruit flavor, were synthesized from (S)-2-acetoxydecyl tosylate as the mutual starting material. The poisonous alkaloid (S)-coniine was also synthesized using enantiomerically pure allyl amine as the key intermediate derived from (S)-acetoxy-6-benzyloxyhexyl tosylate.
- Matsumoto, Kazutsugu,Usuda, Kazumasa,Okabe, Hirokazu,Hashimoto, Manabu,Shimada, Yasutaka
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p. 108 - 115
(2013/04/23)
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- Straightforward access to enantioenriched 2-allylpiperidine: Application to the synthesis of alkaloids
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An efficient stereocontrolled preparation of (2R,RS)-2-allyl-(N- tert-butylsulfinyl)piperidine and its enantiomer is detailed. The sequence requires only two synthetic operations with one-column chromatography and is readily scaled up. The versatility of these chiral building blocks was exemplified by the total or formal synthesis of some natural and unnatural alkaloids.
- Bosque, Irene,González-Gómez, José C.,Foubelo, Francisco,Yus, Miguel
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experimental part
p. 780 - 784
(2012/03/26)
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- A [3+3] cyclization strategy for asymmetric synthesis of alkyl substituted piperidine-2-ones using 1,2-cyclic sulfamidates: A formal synthesis of (S)-coniine from l-norvaline
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Regioselective ring-opening reactions of a set of representative 1,2-cyclic sulfamidates with lithium triethylorthopropiolate proceeded efficiently to deliver the corresponding δ-amino-α,β-unsaturated esters after acidic hydrolysis. Hydrogenation of the unsaturated esters and subsequent thermal cyclization afforded the related alkyl substituted piperidine-2-ones. This approach represents a novel [3+3] cyclization strategy for the asymmetric synthesis of alkyl substituted piperidin-2-ones. Efficiency of the cyclization process is illustrated by a formal asymmetric synthesis of (S)-coniine from l-norvaline.
- Karanfil, Abdullah,Balta, Berrin,Eskici, Mustafa
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p. 10218 - 10229,12
(2020/09/02)
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- Asymmetric synthesis of piperidines and octahydroindolizines using a one-pot ring-closure/N-debenzylation procedure
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The conjugate addition of an enantiopure lithium amide to a ζ-hydroxy-α,β-unsaturated ester followed by a one-pot ring-closure/N-debenzylation protocol has been used in the asymmetric syntheses of (S)-coniine and (R)-δ-coniceine (isolated as the corresponding hydrochloride salts), and (R,R)-1-(hydroxymethyl)octahydroindolizine (the bicyclic fragment of stellettamides A-C).
- Davies, Stephen G.,Fletcher, Ai M.,Hughes, Deri G.,Lee, James A.,Price, Paul D.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Thomson, James E.,Williams, Oliver M.H.
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p. 9975 - 9992
(2012/02/15)
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- Gold(I)-catalyzed intramolecular amination of allylic alcohols with alkylamines
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A 1:1 mixture of (1)AuCl [1 = P(t-Bu)2o-biphenyl] and AgSbF 6 catalyzes the intramolecular amination of allylic alcohols with alkylamines to form substituted pyrrolidine and piperidine derivatives. Gold(I)-catalyzed cyclization of (R,Z)-8-(N-benzylamino)-3-octen-2-ol (96% ee, 95% de) led to isolation of (R,E)-1-benzyl-2-(1-propenyl)piperidine in 99% yield with 96% ee, consistent with the net syn addition of the amine relative to the departing hydroxyl group.
- Mukherjee, Paramita,Widenhoefer, Ross A.
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p. 1334 - 1337
(2011/05/15)
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- Versatile one-pot reductive alkylation of lactams/amides via amide activation: Application to the concise syntheses of bioactive alkaloids (±)-bgugaine, (±)-coniine, (+)-preussin, and (-)-cassine
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Direct entry: One-pot reductive alkylation of lactams/amides with Grignard reagents has been realized via lactam/amide activation with Tf2O. This method opens a direct entry to α-alkylated amines. The versatility of the method is illustrated by the concise syntheses of bioactive alkaloids (±)-bgugaine, (±)-coniine, (+)-preussin, and (?)-cassine.
- Xiao, Kai-Jiong,Wang, Yu,Ye, Ke-Yin,Huang, Pei-Qiang
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supporting information; experimental part
p. 12792 - 12796
(2011/02/22)
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- Broadening the synthetic scope of the iron(III)-Catalyzed aza-prins cyclization
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The nature and influence of the N-sulfonyl group in azaPrins cyclization and the reactivity of the six-membered azacycle generated has been studied. The aza-Prins cyclization of γ,δ-unsaturated amines with a tosyl group at the nitrogen atom produces 2-alkyl-4-halo-1-tosyl-1,2,5,6-tetrahydropyridines with a halovlnyl function, extraordinarily stable to further derivatization and detosylation conditions. To modulate the reactivity of such aza-cycles, a general study of the azaPrins cyclization reaction was performed with several sulfonamides. Ring formation occurs satisfactorily with both N-nosyl and N-mesylamines providing optimal conditions for further synthetic transformations. To exemplify the scope of this methodology, a short synthesis of the alkaloid coniine was successfully carried out.
- Carballo, Ruben M.,Valdomir, Guillermo,Purino, Martin,Martin, Victor S.,Padron, Juan I.
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experimental part
p. 2304 - 2313
(2010/07/10)
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- Asymmetric synthesis of piperidines and octahydroindolizines
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The conjugate addition of a homochiral lithium amide to a ξ-hydroxy-α,β-unsaturated ester, followed by a one-pot, ring-closure-N-debenzylation protocol has been used in the asymmetric syntheses of (S)-coniine and (R)-δ-coniceine (isolated as the corresponding hydrochloride salts) and the bicyclic core of stellettamide A. Georg Thieme Verlag Stuttgart.
- Davies, Stephen G.,Hughes, Deri G.,Price, Paul D.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Thomson, James E.,Williams, Oliver M.H.
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scheme or table
p. 567 - 570
(2010/09/09)
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- Asymmetrie synthesis of unsaturated monocyclic and bicyclic nitrogen heterocycles
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Hydrolysis of scalemic trichloroacetamides Cl3CCONHCH(R) CHCH2 and allylatlon, or acylatlon with but-3-enoic acid, followed by ring-closing metathesis resulted In the formation of unsaturated pyrrolidine and piperidine building blocks. These were employed in the synthesis of (S)-coniine (R = Pr) and a formal synthesis of (+)-anlsomycln (R = p-MeOC 6H4). Extension of this methodology with R = CH 2CHCH2 employing two ring-closing metatheses resulted In the synthesis of unsaturated quinolizidinone and indolizidinone frameworks.
- Nomura, Hiroshi,Richards, Christopher J.
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supporting information; experimental part
p. 2892 - 2895
(2009/12/06)
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- An efficient synthesis of 2- and 2,6-substituted piperidines using Pd II-catalyzed 1,3-chirality transfer reaction
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(Chemical Equation Presented) An efficient and general method for 2- and 2,6-substituted piperidine syntheses using PdII-catalyzed 1,3-chirality transfer reaction has been developed. The various N-protected ζ-amino allylic alcohols cyclize in the presence of PdCl 2(CH3CN)2 to give substituted piperidines with high stereoselectivities. The syntheses of (S)-(+)- and (R)-(-)-coniine were achieved in 3 steps from the optically pure allylic alcohols (S)-14c and (R)-14c, respectively. Although the rates of reactions were significantly accelerated in CH2Cl2, THF gave the highest stereoselectivity. PdCl2(CH3CN)2 was found to be the best catalyst for this transformation. A plausible reaction pathway involving the formation of the Pd π-complex directed by the chiral secondary allylic alcohol followed by syn-azapalladation, and subsequent syn-elimination of PdCl(OH) is proposed.
- Hande, Sudhir M.,Kawai, Nobuyuki,Uenishi, Jun'ichi
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experimental part
p. 244 - 253
(2009/04/11)
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- Asymmetric synthesis of 6-alkyl- And 6-arylpiperidin-2-ones. Enantioselective synthesis of (S)-(+)-coniine
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A variety of diolefinic hydrazides (1) have been assembled in a highly diastereoselective manner by addition of allyllithium to chiral SAMP hydrazones followed by N-acylation with acryloyl chloride. Substrates 1 undergo ring-closing metathesis to give the cyclic enehydrazides (5) which can be easily converted into virtually enantlopure 6-alkyl- or 6-arylpiperidin-2-ones (7). The versatility of this hydrazone addition-RCM protocol has been further exemplified by the conversion of the unsaturated heterocycle 5b into the piperidine alkaloid (S)-(+)-coniine.
- Lebrun, Stephane,Couture, Axel,Deniau, Eric,Grandclaudon, Pierre
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p. 2473 - 2476
(2008/02/05)
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- Preparation of (R)-(+)-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium bromide: synthesis of (S)-(+)-coniine, (R)-(-)-coniceine and (R)-(+)-anabasine
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We describe the transformation of (R)-(-)-1-(2'-hydroxy-1'-phenylethyl)piperidin-2-one 1 into (R)-(-)-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium bromide 2 using POBr3. Reduction of 2 with Red-Al at -78 °C gave (3R,8aR)-(-)-3-phenylhexahydro-2H-oxazolo[3,8-a]-pyridine 3 as a single diastereoisomer. The synthetic potential of these transformation is illustrated by the enantiopure synthesis of (S)-(+)-coniine, (R)-(-)-coniceine and (R)-(+)-anabasine.
- Castro, Alejandro,Ramirez, Johana,Juarez, Jorge,Teran, Joel L.,Orea, Laura,Galindo, Alberto,Gnecco, Dino
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p. 2699 - 2708
(2008/09/19)
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- NICOTINIC ACID DERIVATIVES AS MODULATORS OF METABOTROPIC GLUTAMATE RECEPTORS
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The present invention relates to novel nicotinic acid derivatives, of formula (I), wherein the substituents are defined in the specification, their preparation, their use as pharmaceuticals and pharmaceutical compositions containing them.
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Page/Page column 50-51
(2008/06/13)
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- Enantioselective syntheses of ent-sedridine and (+)-coniine via proline-catalyzed mannich reaction
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Proline-catalyzed three component Mannich reaction using 5-hydroxypentanal as a substrate was achieved in high enantioselectivity to construct a chiral center at C-2 position of 2-substituted piperidine alkaloids. The method was applied to the total syntheses of ent-sedridine and (+)-coniine.
- Nagata, Kazuhiro,Nishimura, Kosuke,Yokoya, Masashi,Itoh, Takashi
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p. 335 - 344
(2007/10/03)
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- Stereodivergent diversity oriented synthesis of piperidine alkaloids
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Alkylidenetitanium reagents enable the reagent-controlled high throughput asymmetric synthesis of 2-substituted piperidines and rapid access to multiple cyclic imines using solid phase synthesis (SPS). The Schrock carbenes, generated by reduction of thioacetals, convert resin-bound esters into enol ethers. Treatment with acid releases amino ketones that are cyclized with TMSCl to give iminium salts. Reduction introduces a chiral centre at C-2, whose absolute stereochemistry is determined by a phenethylamine (PEA) chiral auxiliary. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Adriaenssens, Louis V.,Austin, Carolyn A.,Gibson, Mairi,Smith, David,Hartley, Richard C.
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p. 4998 - 5001
(2007/10/03)
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- Asymmetric allylboration of cyclic imines and applications to alkaloid synthesis
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Treatment of cyclic imines with 3,3′-disubstituted binaphthol modified allylboronates provides the expected allylated products in good yields and with high stereoselectivities (91-99% ee). The products may be readily transformed into various alkaloids. Copyright
- Wu, T. Robert,Chong, J. Michael
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p. 9646 - 9647
(2007/10/03)
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- Stereoselective synthesis of chiral piperidine derivatives employing arabinopyranosylamine as the carbohydrate auxiliary
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Stereoselective synthesis of 2-substituted dehydropiperidinones and their further transformation to variously disubstituted piperidine derivatives was achieved employing D-arabinopyranosylamine as the stereodifferentiating carbohydrate auxiliary. A domino Mannich-Michael reaction of 1-methoxy-3-(trimethylsiloxy)butadiene (Danishefsky's diene) with O-pivaloylated arbinosylaldimines furnished N-arabinosyl dehydropiperidinones in high diastereoselectivity. Subsequent conjugate cuprate addition gave 2,6-cis-substituted piperidinones, while enolate alkylation furnished 2,3-trans-substituted dehydropiperidinones. Electrophilic substitution at the enamine structure afforded 5-nitro- and 5-halogen dehydropiperidinones of which the latter were applied in palladium-catalyzed coupling reactions. The absolute configuration of the obtained products was proven by NMR and X-ray structure analysis as well as by syntheses of the alkaloids (+)-coniine and (+)-dihydropinidine.
- Kranke, Birgit,Kunz, Horst
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p. 625 - 641
(2007/10/03)
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- METHOD FOR SYNTHESISING OPTICALLY ACTIVE PIPERIDINES BY THE HYDROGENATION OF OPTICALLY ACTIVE PYRIDINES
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The invention relates to a method for preparing optically active piperidines by the hydrogenation of pyridines using a suitable catalyst. Said method enables the preparation of a plurality of piperidine derivatives with high optical purity and in high yields.
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Page/Page column 14; 15
(2010/02/12)
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- Stereoselective synthesis of enantiomerically pure piperidine derivatives by N-galactosylation of pyridones
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Stereoselective desymmetrization of 4-pyridone has been achieved through selective N-galactosylation, activation of the N-(galactosyl)pyridone by O-silylation and immediate addition of Grignard compounds. Chiral piperidine derivatives, e.g. (S)-(+)-coniine and (5S,9S)-(+)-indolozidine 167B, were synthesised in enantiomerically pure form using these highly regio- and stereoselective reactions. After N-galactosylation of 2-pyridone and O-silylation of the N-galactosyl-2-pyridone, addition of a Grignard compound proceeded with high 1,4-regioselectivity and complete diastereoselectivity, to furnish 4-substituted 5,6-dehydro-2-piperidones. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Klegraf, Ellen,Follmann, Markus,Schollmeyer, Dieter,Kunz, Horst
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p. 3346 - 3360
(2007/10/03)
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- Syntheses of pyridin-4-ylium chirons: Applications in a synthesis of (+)-coniine
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The compounds (3R,5S)-(+)-5-methyl-3-phenyl-2,3,5,6,7,8-hexahydro- oxazolo[3,2-a]pyridin-4-ylium iodide 4 and (3R,5S)-(+)-5-n-propyl-3-phenyl-2,3, 5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide 5 were synthesized in two steps starting from the bicyclic thiolactam trans (3R,2aS)-(-)-5-thio-3- phenyl-2,3,6,7,8,2a-hexahydro-oxazolo[3,2-a]pyridine 1. In addition, starting from 5 an enantiospecific synthesis of (+)-coniine 7 was achieved.
- Roa, Luis F.,Gnecco, Dino,Galindo, Alberto,Teran, Joel L.,Bernes, Sylvain
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p. 847 - 850
(2007/10/03)
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- Asymmetric synthesis of 2-substituted piperidines using a multi-component coupling reaction: Rapid assembly of (S)-coniine from (S)-1-(1-phenylethyl)-2-methyleneaziridine
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(S)-Coniine is made using a reaction which assembles the piperidine ring by the sequential formation of four new chemical bonds and installs the C-2 stereogenic centre with high levels of diastereocontrol (90% de).
- Hayes,Shipman,Twin
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p. 1784 - 1785
(2007/10/03)
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- New methodology for the synthesis of enantiopure (3R,2aR)-(-)-3-phenyl-hexahydro-oxazolo[3,2-a]-pyridin-5-one: A synthesis of (S)-(+)-coniine
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A new and efficient methodology for the enantiopure synthesis of (3R,2aR)-(-)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one 3 starting from (1′R)-(-)-1-(2′-hydroxy-1′-phenyl-ethyl)-(1H)-pyridin-2-one 1 is described. In addition, the enantiospecific synthesis of (S)-(+)-coniine hydrochloride 6 in good yield from 3 is reported.
- Teran,Gnecco,Galindo,Juarez,Bernes,Enriquez
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p. 357 - 360
(2007/10/03)
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- Stereocontrolled alkylation of chiral pyridinium salt toward a short enantioselective access to 2-alkyl- and 2,6-dialkyl-1,2,5,6- tetrahydropyridines
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Treatment of salts 1a-b with Grignard reagents gives, after reduction of the resulting unstable dihydropyridines 7, the tetrahydropyridines 8a-c, with modest selectivities but in very few steps and under practical conditions. Higher stereo and regioselectivities are obtained with salt 1c which gives the tetrahydropyridines 15a-e. In addition, the dihydropyridine intermediates 11b cyclize to give the new oxazolidine derivatives 12a-e, which turn out to be good precursors of the 2,6-trans-disubstituted tetrahydropyridines 21a-e. Selective syntheses of (-)-lupetidin, (+)-solenopsin, and indolizidines (-)-5 and (-)-6 are presented as representative examples of applications.
- Guilloteau-Bertin, Berangere,Compere, Delphine,Gil, Laurent,Marazano, Christian,Das, Bhupesh C.
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p. 1391 - 1399
(2007/10/03)
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- Efficient Routes to Chiral 2-Substituted and 2,6-Disubstituted Piperidines
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The syntheses of chiral 2-substituted and 2,6-disubstituted piperidines, and piperidin-2-ylphosphonates, via benzotriazole methodology are described.
- Katritzky, Alan R.,Qiu, Guofang,Yang, Baozhen,Steel, Peter J.
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p. 6699 - 6703
(2007/10/03)
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- Enantioselective α-alkylation of piperidine via chiral perhydropyrido [2,1-b] [1,3,4]-oxadiazinone: An easy route for the synthesis of both enantiomers of coniine
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Enantioselective direct alkylation of piperidine involving chiral perhydropyrido [2,1-b] [1,3,4]-oxadiazinone using either form of mandelic acid as chiral auxiliary is reported. The application of the strategy is demonstrated by the synthesis of(R)- as well as (S)- coniine.
- Pandey, Ganesh,Das, Parthasarathi
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p. 9073 - 9076
(2007/10/03)
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- A new asymmetric entry to 2-substituted piperidines. A concise synthesis of (+)-coniine, (-)-pelletierine, (+)-δ-coniceine, and (+)-epidihydropinidine
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A new asymmetric route to 2-substituted piperidines involving the Sharpless asymmetric dihydroxylation (AD) of 5-hexenylazide 1 and an intramolecular aminocyclization as crucial steps and its application to the asymmetric synthesis of four piperidine alkaloids, (+)-coniine 2, (-)-pelletierine 3, (+)-δ-coniceine 4, aND (+)-epidihydropinidine 5 is presented.
- Takahata, Hiroki,Kubota, Minoru,Takahashi, Seiki,Momose, Takefumi
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p. 3047 - 3054
(2007/10/03)
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- A New Asymmetric Synthesis of Both Enantiomers of Coniine by 1,2-Addition of RLi/YbCl3 to Aldehyde SAMP Hydrazones
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Both enantiomers of the hemlock alkaloid coniine 8 are prepared by asymmetric synthesis in 98percent ee using only one enantiomer of the auxiliary.The key step of the synthesis consists in the 1,2-addition of organoytterbium reagents to aldehyde SAMP hydrazones with virtually complete asymmetric induction, followed by N-N bond cleavage and cyclization. Key Words: Coniine, enantioselective synthesis of/SAMP hydrazones, 1,2-addition of/Organoytterbium reagents/Synthon control of enantioselectivity.
- Enders, Dieter,Tiebes, Joerg
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p. 173 - 178
(2007/10/02)
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- Asymmetric Tandem Mannich-Michael Reactions of Amino Acid Ester Imines with Danishefsky's Diene
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Imines 1 derived from aromatic, aliphatic, and functionalized aldehydes and various amino acid esters react with Danishefsky's diene under Lewis acid catalysis via a tandem Mannich-Michael mechanism to give cyclic 6-substituted 2,3-didehydro-4-piperidinones in good to high yields and with diastereomeric ratios reaching from 92:8 up to 97:3.The chiral auxiliary is removed by conversion of the α C atom of the amino acid into an acetalic center, employing a Curtius reaction as the key step.For the elucidation of the absolute configuration, the alkaloids (S)-coniine and (R)-δ-coniceine are synthesized from the enaminones 5i and 5r.
- Waldmann, H.,Braun, M.
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p. 4444 - 4451
(2007/10/02)
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- Conversion of N-acyl-2,3-dihydro-4-pyridones to 4-chloro-1,2-dihydropyridines using the Vilsmeier reagent
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N-Acyl-2,3-dihydro-4-pyridones are converted to 1-acyl-4-chloro-1,2-dihydropyridines in one step using one equivalent of Vilsmeier reagent. This conversion was utilized in an asymmetric synthesis of (-)-coniine.
- Al-Awar,Joseph,Comins
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p. 7635 - 7638
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF (+)- AND (-)-CONIINES AND (-)-SEDAMINE BY DIASTEREOSELECTIVE ALKYLATION REACTION OF ETHOXYPIPERIDININE
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Diastereoselective alkylation reaction of the chiral 6-ethoxypiperidinones (4) and (5) has been developed and successfully applied to the asymmetric synthesis of piperidine alkaloids, (+)- and (-)-coiines (11) and (12), (-)-sedamine (21), and (-)-allosedamine (22).
- Kiguchi, Toshiko,Nakazono, Yoko,Kotera, Sanae,Ninomiya, Ichiya,Naito, Takeaki
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p. 1525 - 1535
(2007/10/02)
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