- Titanium-mediated diastereoselective formation of (E)- or (Z)-2-substituted 1-vinylcyclopropanols: Scope and limitation, applications
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Titanium-mediated cyclopropanation of α,β-unsaturated esters failed to provide 1-vinylcyclopropanol derivatives in useful yields, but (E)-2-substituted-1-vinylcyclopropanols were formed diastereoselectively from O-protected β-oxo- and β-halo esters, with the allylic double bond being created subsequently (Knoevenagel condensation or dehydrohalogenation). Titanium-mediated cyclopropanation of homoallyl alk-2-enoates, on the other hand, directly provided the corresponding Z diastereomers. Palladium(0)-catalysed azidation of their sulfonic esters (tosylate, mesylate), azide reduction, and subsequent double bond cleavage afforded (E)- or (Z)-2-alkyl-2,3-methanoamino acids, although improvements are required to perform the total asymmetric syntheses of molecules with three membered-rings by these methods. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Racouchot, Sandrine,Sylvestre, Isabelle,Ollivier, Jean,Kozyrkov, Yuri Yu.,Pukin, Alexei,Kulinkovich, Oleg G.,Salauen, Jacques
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p. 2160 - 2176
(2007/10/03)
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- A convenient approach to substituted 1-(1-alkenyl)cyclopropanols: A new preparation of 2,3-methanoamino acids
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The diastereoselective titanium(IV)-mediated cyclopropanation of ethyl 3,3-diethoxypropionate by Grignard reagents, followed by modified Knoevenagel condensation with malonic acid under microwave irradiation, allow the preparation of (E)-1-(1-alkenyl)cyclopropanol derivatives, suitable precursors of πn-1,1-dimethyleneallylmetal species. The azidation of such complexes, followed by a reduction-oxidation sequence led to pure (E)-2,3-methanoamino acids. (C) 2000 Elsevier Science Ltd.
- Kozyrkov,Pukin,Kulinkovich,Ollivier,Salaun
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p. 6399 - 6402
(2007/10/03)
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- New Chiral Didehydroamino Acid Derivatives from a Cyclic Glycine Template with 3,6-Dihydro-2H-1,4-oxazin-2-one Structure: Applications to the Asymmetric Synthesis of Nonproteinogenic α-Amino Acids
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New chiral (Z)-α,β-didehydroamino acid (DDAA) derivatives with 3,5-dihydro-2H-1,4-oxazin-2-one structure 11a-f have been stereoselectively prepared after condensation of chiral glycine equivalent 7 with aldehydes in the presence of K2CO3 under mild solid-liquid phase-transfer catalysis reaction conditions. These new systems have been used in diastereoselective cyclopropanation reactions using Corey's ylide for the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acids (ACCs) such as allo-corononamic and allo-norcoronamic acids. The hydrogenation reaction of these systems at ambient pressure in the presence of formaldehyde affords saturated oxazinones and N-methylated oxazinones which have been transformed into the N-methyl-α-amino acids (N-MAAs) (S)-2-(methylamino)butanoic acid and (S)-N-methylleucine. In addition, the parent α,β-didehydroalanine derivative 11g has been prepared by a direct aminomethylation-elimination sequence from 7 and Eschenmoser's salt and has been used in Diels-Alder cycloaddition with endo selectivity for the synthesis of the enantiomerically pure bicyclic α-amino acids (-)-2-aminobicyclo[2.2.1]heptane-2-carboxylic and (-)-2-aminobicyclo[2.2.2]octane-2-carboxylic acids.
- Chinchilla, Rafael,Falvello, Larry R.,Galindo, Nuria,Najera, Carmen
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p. 3034 - 3041
(2007/10/03)
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- Stereoselective synthesis of highly functionalized cyclopropanes. Application to the asymmetric synthesis of (1S,2S)-2,3-methanoamino acids
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One-pot palladium(0)-catalyzed alkylation and S(N') cyclization of 1,4- dichlorobut-2-ene 1 by the anion of α-substituted carbonitriles 2a-d can provide highly functionalized cyclopropanes (E)-4a-d, diastereoselectivity, (de 88-100%). Several attempts to achieve the asymmetric synthesis of the 1- amino-2-ethenylcyclopropanecarbonitrile (E)-9, by means of this new procedure, i.e., using chiral palladium ligands, chiral aminoacetonitriles (- )- and (+)-12 (from 1-hydroxypinanone) or chiral allyl chlorides (4S)-20b-d and (4R)-20e (from (2S) ethyl lactate) have pointed up the reversibility of the palladium-catalyzed cyclization step, responsible for the low enantioselectivity observed (ee ≤ 32%) and for the formation of byproducts, i.e., azepine derivatives 8a,b arising from subsequent aza Cope ring expansion. Molecular mechanics calculations using a modified MM2 type force field adapted to the π-allyl palladium complexes have explained these results. However, When performed under the Mitsunobu reaction conditions (DEAD, PMe3), therefore, in the absence of palladium catalyst, the S(N'), cyclization occurred also diastereoselectively (de > 88%) and provided the enantiomerically enriched 1-amino-2-propenylcyclopropanecarbonitrile (E)-22 (ee > 83%) suitable precursor of (1S,2S)-2,3-methanoamino acids.
- Dorizon, Philippe,Su, Guifa,Ludvig, Gitte,Nikitina, Lilyia,Paugam, Renee,Ollivier, Jean,Salauen, Jacques
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p. 4712 - 4724
(2007/10/03)
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- Asymmetric synthesis of substituted 1-aminocyclopropane-1-carboxylic acids from a new chiral glycine equivalent with 3,6-dihydro-2H-1,4-oxazin-2- one structure
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Condensation of the new chiral glycine equivalent 10 with aldehydes at room temperature in the presence of K2CO3 under solid-liquid phase- transfer-catalysed conditions afforded stereoselectively new chiral (Z)- α,β-didehydroamino ac
- Chinchilla, Rafael,Falvello, Larry R.,Galindo, Nuria,Najera, Carmen
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p. 2223 - 2227
(2007/10/03)
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- Enantioselective total syntheses of cyclopropane amino acids: Natural products and protein methanologs
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The syntheses of (-)-allo-coronamic acid, (-)-allo-norcoronamic acid, (-)-(Z)-2,3-methanohomoserine, (-)-(Z)-2,3-methanomethionine, and (2S,3R)-Cbz-cyclo-Asp-OMe have been achieved in 45-68% overall yields from suitable intermediates derived from homochiral aminopentenoates which were obtained, in turn, from D-glyceraldehyde. The key synthetic step involves the quantitative and highly diastereoselective cyclopropanation of such precursors. The factors dealing with the control of stereoselectivity are highlighted and the main features in side-chain functionalization to the respective target molecules are discussed.
- Jimenez, Jose M.,Rife, Joan,Ortuno, Rosa M.
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p. 537 - 558
(2007/10/03)
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- Synthesis of enantiomerically pure 2-alkyl 1-amino cyclopropane-1-carboxylic acid
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Asymmetric synthesis of 1-amino 2-alkyl cyclopropane carboxylic acids using (1R,2R,5R)-2-hydroxy pinan-3-one as the chiral auxiliary and Corey's ylide as reagent is described.
- Calmes, Monique,Daunis, Jacques,Escale, Francoise
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p. 395 - 396
(2007/10/03)
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- Enantioselective Total Syntheses of (-)-allo-Coronamic Acid, (-)-(Z)-2,3-Methanohomoserine, and (2S,3R)-Cbz-cyclo-Asp-OMe
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The title amino acids have been synthesized in 45, 47, and 63percent overall yields, respectively, from enantiopure aminopentenoates, easily available from D-glyceraldehyde as a source of chirality, following divergent pathways from similar diols as commo
- Jimenez, Jose M.,Rife, Joan,Ortuno, Rosa M.
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p. 1849 - 1852
(2007/10/03)
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- Practical Stereoselective Syntheses of All Four Stereoisomers of Coronamic Acid (2-Ethyl-1-aminocyclopropane-1-carboxylic acid)
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All four stereoisomers of coronamic acid were synthesized from both enantiomers of 1,2-butanediol.Cyclopropanation of cyclic sulfate with the dibenzyl malonate anion gave cyclopropane dibenbzyl ester in a quantitative yield.Transformation into a protected amino acid was acieved by stereoselective hydrolysis and Curtius rearrangement as the key step.Saponification and subsequent acidic hydrolysis in one pot and ion exchange gave a free amino acid in a high yield.
- Toshima, Hiroaki,Ochihara, Akitami
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p. 497 - 500
(2007/10/02)
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- A Simple Synthesis of (-)-(1S,2R)-Allocoronamic Acid in its Enantiomerically Pure Form
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(-)-(1S,2R)-Allocoronamic acid was synthesized in its enantiomerically pure form by starting from the chiral azlactone derived from 1,2-O-isopropylidene-D-glyceraldehyde in an overall yield of 37percent.
- Cativiela, Carlos,Diaz-de-Villegas, Maria D.,Jimenez, Ana I.
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p. 177 - 182
(2007/10/02)
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- Total asymmetric syntheses of (1S,2S)-norcoronamic acid, and of (1R,2R)- and (1S,2S)-coronamic acids from the diastereoselective cyclization of 2-(N-benzylideneamino)-4-chlorobutyronitriles
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(3R)-2-(N-Benzylideneamino)-4-chloro-3-methylbutyronitrile 3, prepared from the commercially available methyl (2S)-3-hydroxy-2-methyl propionate 5 (96percent ee), readily underwent potassium carbonate induced cyclization to provide, after acid hydrolysis (6 N HCl) and chromatography, the (1S,2S)-norcoronamic acid 1a with 88percent diastereoselectivity and above 95percent enantiomeric excess.From (2R)-2-(hydroxymethyl)butyl acetate 23 (above 88percent ee) obtained by enzymatic enantioselective hydrolysis with lipase PS, was prepared the (3S)-2-(N-benzylideneamino)-3-(chloromethyl)valeronitrile 29, which after base-induced cyclization (K2CO3) and acid (6 N HCl) or basic (0.8 N NaOH) hydrolysis led to the non-natural (1R,2R)-coronamic acid 18 (>88percent ee).Also from this same acetate (2R)-23 was prepared the (3R)-3-(chloromethyl)-2-pentanenitrile 37, which provided the (1S,2S)-coronamic acid 17 (above 88percent ee) after base-induced cyclization (K2CO3 or LDA) and acid hydrolysis (6 N HCl).It is noteworthy that these short synthetic sequences, which do not require any expensive chiral auxiliary or optically active precursors, do not alter the enantiomeric purity of the stereogenic centers of these 2,3-methanoamino acids.However, the E diastereoselctivity of these cyclizations was not improved by using bulky N-(diphenylmethylene)amino substituent, contrary to results of some molecular mechanic calculations (MAD).
- Gaucher, Anne,Ollivier, Jean,Marguerite, Jacqueline,Paugam, Renee,Salauen, Jacques
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p. 1312 - 1327
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF CIS AND TRANS 2-METHYL AND 2-ETHYL 1-AMINO CYCLOPROPANECARBOXYLIC ACIDS
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A new four step asymmetric synthesis of 2-methyl and 2-ethyl 1-amino cyclopropane carboxylic acids resulted from the cycloaddition of diazomethane to the corresponding chirally derivatized dehydro-aminoacid.
- Alami, Adiba,Calmes, Monique,Daunis, Jacques,Escale, Francoise,Jacquier, Robert,et al.
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p. 175 - 178
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF REGIO-SPECIFICALLY 2-ALKYLATED-3-DEUTERIATED-1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACIDS
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A simple procedure for the large scale preparations of regio-specifically 2-alkylated-3-deuteriated-1-aminocyclopropane-1-carboxylic acids from 1-deuterio-1,2-dibromoalkanes is described.
- Baldwin, Jack E.,Adlington, Robert M.,Rawlings, Bernard J.
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p. 481 - 484
(2007/10/02)
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- THE RESOLUTION OF RACEMIC 2-ALKYL-1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACIDS
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Practical procedures for the resolution of racemic modification of (1R, 2S)- and (1S, 2R)-1-amino-2-ethylcyclopropane-1-carboxylic acid 1a,b,(1R, 2S)- and (1S, 2R)-1-amino-2-methylcyclopropane-1-carboxylic acid 2a,b, and (1R, 2R)- and (1S, 2S)-1-amino-2-methylcyclopropane-1-carboxylic acid 3a,b are described; the structures as 1a,2a, and 3a were confirmed by X-ray crystallographic methods.
- Baldwin, Jack E.,Adlington, Robert M.,Rawlings, Bernard J.,Jones, Richard H.
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p. 485 - 488
(2007/10/02)
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- SYNTHESIS OF 1-AZIDOCYCLOPROPANECARBOXYLATES FROM 2-AZIDO-2-ALKENOATES
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Addition of diazomethane to 2-azido-2-alkenoates followed by pyrolysis of the resulting pyrazoline derivatives affords the title compounds.
- Hiyama, Tamejiro,Kai, Mariko
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p. 2103 - 2104
(2007/10/02)
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