Synthese ungesättigter Aminosäuren durch [3,3]‐sigmatrope Umlagerung chelatverbrückter Glycinesterenolate

Kazmaier, Uli

doi:10.1002/ange.19941060923

Cited by 53 publications

(13 citation statements)

References 34 publications

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“…Moreover, the Irelend-Claisen rearrangement of a-substituted acetic acid esters of the mentioned fluorinated allylic alcohols such as achloroacetic esters or propionic esters, led to the corresponding 2-substituted 4-fluoroalk-4-enoic acids in moderate yields [9]. The reaction was shown to work also with N-protected glycine esters to give 2-amino-4-fluoroalk-4-enoic acids in excellent yields in a modified Kazmaier variation [10] of the IrelandClaisen rearrangement [11]. Furthermore, we have shown that N-benzoyl protected fluorinated allylic esters of alanine or phenylglycine gave the corresponding N-benzoyl 2-amino-4-fluoro-2-methyl(or phenyl)-alk-4-enoic acids in almost quantitative yield following the mechanism of the Steglich variant [12] of the Ireland-Claisen rearrangement [13].…”

Section: Introductionmentioning

confidence: 96%

Synthesis of optically active 2-fluoroalk-1-en-3-yl esters and chirality transfer in their Claisen-type rearrangements

Marhold

Wittmann

Takahashi

et al. 2007

Journal of Fluorine Chemistry

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Section: Introductionmentioning

confidence: 96%

Synthesis of optically active 2-fluoroalk-1-en-3-yl esters and chirality transfer in their Claisen-type rearrangements

Marhold

Wittmann

Takahashi

et al. 2007

Journal of Fluorine Chemistry

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“…Attempts to achieve a Claisen rearrangement on 12 under Kazmaiers, [12] Irelands, [13] or Johnsons [14] conditions failed.…”

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confidence: 93%

Diastereoselective Total Synthesis of (±)‐Codeine

Varin

Barré

Iorga

et al. 2008

Chemistry A European J

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Codeine 1 and morphine 2, the principal constituents of opium, continue to attract the attention of organic chemists thanks to both their biological activities and their unique structure.[1] Their complex pentacyclic skeleton, which includes a quaternary carbon center, has stimulated extensive efforts. To date there have been more than 20 total syntheses of codeine (1), morphine (2), and thebaine (3).[2] We were interested in the synthesis of codeine for two reasons: first, codeine was found to be an allosteric potentiating ligand of nicotinic receptors, [3] and second we have a general program underway in the laboratory in which we have shown that tricyclic spirocyclohexadienones are valuable intermediates for the synthesis of natural products in the Amaryllidacea galanthamine-type, maritidine-type, and Aspidosperma alkaloids. [4] In an effort to develop new allosteric potentiating ligands of nicotinic receptors with a codeine-type scaffold, we initiated our own studies of a total synthesis of codeine. Herein we disclose a total diastereoselective synthesis of (AE )-codeine (1), which involves a new construction of the morphinan skeleton. The present study provides an efficient method for the elaboration of the quaternary carbon at C-13 and for the highly diastereoselective introduction of the C-14 stereogenic center of the morphinan system.Our retrosynthetic analysis of (AE )-codeine (1) is shown in Scheme 1. Codeine could be obtained from amine intermediate 4 by using an intramolecular hydroamination reaction to form the D ring. Compound 4 could in turn be prepared from aldehyde 5. In our synthetic pathway, we planned to use for the first time a Claisen-type rearrangement to introduce the C-14 substituent. This type of rearrangement applied to compound 6 would provide a precursor of the aldehyde 5 and control the stereochemistry of the substituent at C-14 of 5. The tricyclic amine 6 would be obtained from the spirocyclohexadienone 7 by a lactone ring opening with an amine followed by a spontaneous intramolecular Michael

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“…[23] These enolates are excellent nucleophiles for transition-metal-catalyzed allylic alkylations, [24] giving rise to γ,δunsaturated amino acids. The same structural motif can be obtained through a chelate-enolate Claisen rearrangement, [25] an approach well suited for highly functionalized amino acids [26] and peptides. [27] Here we wish to report on an application of this protocol for the synthesis of Aoe and chlamydocin.…”

Section: Introductionmentioning

confidence: 99%