- 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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- Asymmetric syntheses of 1-amino-2-phenyl(alkyl)cyclopropanecarboxylic acids by diastereoselective cyclopropanation of highly functionalized monochiral olefines
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Monochiral α-benzamidocinnamic esters of N-methylephedrine or mandelic derivatives and benzylidene or alkylidene diketopiperazines, all obtained from oxazolones, react with diazomethane to give moderate to high diastereomeric excesses (d.e.) of pyrazoline
- Alcaraz,Alcaraz, Carmen,Fernandez,Fernaendez, Ma. Dolores,De Frutos,De Frutos, Ma. Pilar,Marco,Marco, Josee L.,Bernabe,Bernabe, Manuel,Foces-Foces,Foces-Foces, Concepcion,Cano,Cano, Felix H.
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p. 12443 - 12456
(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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- Enantioselective synthesis of (+)-(1R,2S)-allocoronamic acid
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The asymmetric synthesis of (+)-(1R,2S)-allocoronamic acid is reported. Diazomethane addition to (Z)-N-(tert-butoxycarbonyl)ethyldehydroalanyl-L-prolin-anhydride, easily prepared from (Z)-2-phenyl-4-propylidene-5(4H)-oxazolone and L-proline, gave in high diastereomeric excess the corresponding spiropyrazoline, which was transformed on photolysis and acid hydrolysis of the resulting spirocyclopropane, into (+)-(1R,2S)-1-amino-2-ethyl-cyclopropanecarboxylic acid.
- Alcaraz,Herrero,Marco,Fernandez-Alvarez,Bernabe
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p. 5605 - 5608
(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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