Synthese chiraler γ,δ‐ungesättigter Aminosäuren durch asymmetrische Ester‐Enolat‐Claisen‐Umlagerung

Abstract

Die N‐geschützten Aminosäureallylester 1 liefern in einer Ester‐Enolat‐Claisen‐Umlagerung die entsprechenden chiralen α‐Allylaminosäuren 2 in exzellenten Ausbeuten und Stereoselektivitäten. Das zur Induktion eingesetzte Chinin kann bei der Aufarbeitung nahezu vollständig zurückgewonnen werden. Umkristallisieren mit 1‐Phenylethylamin ergibt enantiomerenreines 2. R  Alkyl, Phenyl.

Thiol‐Ene Click Reactions – Versatile Tools for the Modification of Unsaturated Amino Acids and Peptides

“…Such nonpolar substituents can be used to decrease the polarity of amino acids and peptides. Starting from cinnamyl alcohol, β-phenylated amino acid 3 could easily be obtained by a chelated Claisen rearrangement, [27] while δ-phenylated derivative 4 was obtained by allylic alkylation. These substituents should increase the water solubility of a given peptide.…”

“…[26] To test the scope and limitations of this protocol, we next investigated the addition of thiols to substituted allylglycine derivatives (Scheme 1). Starting from cinnamyl alcohol, β-phenylated amino acid 3 could easily be obtained by a chelated Claisen rearrangement, [27] while δ-phenylated derivative 4 was obtained by allylic alkylation. [20] Scheme 1.…”

Application of the Ester Enolate Claisen Rearrangement in the Synthesis of Amino Acids Containing Quaternary Carbon Centers

“…Because of the fixation of the enolate geometry by chelation, the rearrangement proceeds in a highly diastereoselective fashion. Further investigations, particularly into the asymmetric synthesis of quaternary amino acids by rearrangement of chiral allylic esters and rearrangements in the presence of chiral ligands, are in progress.…”

Application of the Palladium Catalyzed N-Allylation to the Modification of Amino Acids and Peptides

“…5 If these reactions are carried out in the presence of chiral ligands such as quinine or quinidine, optically active amino acids are obtained with high ee's. 6 Due to the preferred chairlike transition state the syn-configured g,d-unsaturated amino acids can be obtained in a highly stereoselective fashion. On the other hand, the anticonfigured products can be synthesized by means of a pal-ladium catalyzed allylic substitution reaction using chelated amino acid esters as nucleophiles (Scheme 2b).…”