- Hepatitis C inhibitor peptides
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Disclosed herein are hepatitis C viral protease inhibitors of formula (I): wherein a is0or1; b is0or1; Y is H or C1-6alkyl; B is H, an acyl derivative or a sulfonyl derivative; R6, when present, is C1-6alkyl substituted wi
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- 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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- 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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- 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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- Palladium (O) catalyzed tandem alkylation and SN′ cyclization of 1,4-dichlorobut-2-ene by the N-(diphenylmethylene)acetonitrile. a stereoselective synthesis of 1-aminocyclopropanecarboxylic acids
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Racemic coronamic acid has been prepared with 100% diastereoselectivity from one pot palladium (O) catalyzed alkylation and SN′ cyclization of 1,4-dichlorobut-2-ene by the benzophenone Schiff base of aminoacetonitrile.
- Gaucher, Anne
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p. 2979 - 2982
(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 via Heterocyclic Intermediates, XLVII. Asymmetric Synthesis of (+)-(1R,2S)-allo-Coronamic Acid
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allo-Coronamic acid (1) was synthesized in five steps enantiomerically and diastereomerically virtually pure by starting from the bislactim ethers of cyclo(-L-Val-Gly-) (3a) or cyclo(-L-tert-Leu-Gly-) (3b) in an overall yield of 31percent.The key step of this synthesis is the intramolecular alkylation of the lithium azaenolate derived from the allylic chloride 4. Key Words: Amino acids / Cyclopropanes / Cyclopropanation, diastereoselective / Bislactim ether method
- Groth, Ulrich,Halfbrodt, Wolfgang,Schoellkopf, Ulrich
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p. 351 - 356
(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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- Asymmetric syntheses of 1-aminocyclopropane-1-carboxylic acid derivatives
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Optically active D-erythro-4-(tert-butoxycarbonyl)-3-(dimethoxyphosphoryl)-5,6-diphenyl-2,3,5,6- tetrahydro-4H-1,4-oxazin-2-one (13) can be efficiently condensed with various aldehydes via the Emmons-Horner-Wadsworth procedure to provide α,β-dehydrolacton
- Williams, Robert M.,Fegley, Glenn J.
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p. 8796 - 8806
(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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- NORCORONATINE AND N-CORONAFACOYL-L-VALINE, PHYTOTOXIC ANALOGUES OF CORONATINE PRODUCED BY A STRAIN OF PSEUDOMONAS SYRINGAE PV. GLYCINEA
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Key Word Index - Pseudomonas syringae pv. glycinea; toxin; leaf chlorosis; coronatine; norcoronatine; N-coronafacoyl-L-valine; biosynthesis; coronafacic acid; 1-amino-2-methylcyclopropane-1-carboxylic acid.Abstract - Compounds in liquid cultures of the phytopatogenic bacterium Pseudomonas syringae pv. glycinea that cause chlorosis after application to young bean leaves have been investigated.Known compounds that were isolated and identified were coronatine, the major component, and N-coronafacoyl-L-valine, which are both biologically active, and cornafacic acid which is inactive.In addition a new minor component was isolated and purified.Mass spectrometry indicated that this was an amide of coronafacic acid, bearing one less methylene group than coronatine.Mass spectral and NMR data, together with a study of the products from acid hydrolysis of the new compound, established its structure to be norcoronatine (i.e. a methyl substituent in place of the 2-ethyl substituent on the cyclopropyl moiety of coronatine).The probable biosynthetic derivation of norcoronatine is discussed.
- Mitchell, Robin E.
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p. 1485 - 1488
(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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