Journal ArticleDOI
Herstellung enantiomerenreiner, α‐alkylierter Lysin‐, Ornithin‐ und Tryptophan‐Derivate
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TLDR
Several α-alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1-(tert-butyloxycarbonyl)-3-(bromomethyl)indole).Abstract:
Synthesis of Enantiomerically Pure, α-Alkylated Lysine, Ornithine, and Tryptophan Derivatives
The imidazolidinones 9 and 10 as well as the oxazolidinone 18a were prepared in several steps by known methods from lysine and ornithine with an overall yield of ca. 20%. After double deprotonation with LDA, the corresponding dianionic derivatives could be diastereoselectively alkylated with electrophiles (MeI, C6H5CH2Br, C6H5CHO, CH3CHO). Acid hydrolysis led to the two enantiomeric 2-methyl- and 2-benzyllysines and to the enzyme inhibitor (S)-2-methylornithine. Several α-alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1-(tert-butyloxycarbonyl)-3-(bromomethyl)indole (26). Alkaline hydrolysis of the five-membered auxiliary ring of 30b followed by treatment with HCl afforded (S)-2-methyltryptophan (31).read more
Citations
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Stereoselective synthesis of quaternary α-amino acids. Part 1: Acyclic compounds
Journal ArticleDOI
Chemistry of the Hexahydropyrrolo[2,3-b]indoles: configuration, conformation, reactivity, and applications in synthesis.
David Crich,Abhisek Banerjee +1 more
TL;DR: The stereoselective formation of 2-endo-substituted hexahydropyrrolo[2,3-b]indoles from 2-subStituted tryptamine derivatives, especially tryptophan, is discussed and parallels are drawn to the Woerpel model for the reactivity of analogous five-membered cyclic oxacarbenium ions.
Journal ArticleDOI
How we drifted into peptide chemistry and where we have arrived at
TL;DR: A brief summary is given of the results obtained in the ensuing discovery tour of β-peptides built of homologated proteinogenic amino acids, which form secondary structures with short chain lengths and they have unexpected physiological properties, rendering them candidates for peptidic drugs.
Journal ArticleDOI
A New General Approach to Enantiomerically Pure Cyclic and Open-Chain (R)- and (S)-α,α-Disubstituted α-Amino Acids
Daniel Obrecht,Clive Spiegler,Peter Schönholzer,Klaus Müller,Heinz Heimgartner,Friedrich Stierli +5 more
TL;DR: A wide range of cyclic and open-chain alpa, alpha-disubstituted alpha-amino acids 1a-p were prepared and the absolute configurations of the alpha,alpha-disubsided amino acids were determined from X-ray structures of the diastereoisomers 20, 21g', 22d.
Journal ArticleDOI
Application of the Chelate-Enolate Claisen Rearrangement to The Synthesis of γ,δ-Unsaturated Amino Acids
TL;DR: In this article, N-protected amino acid allylic esters with LDA at −78°C and subsequent addition of a metal salt presumably results in the formation of a chelated metal enolate that undergoes Claisen rearrangement upon warming up to room temperature, giving rise to γ, Δ-unsaturated amino acids.
References
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Journal ArticleDOI
Substitution of HMPT by the cyclic urea DMPU as a cosolvent for highly reactive nucleophiles and bases
TL;DR: The cyclic urea DMPU (N, N, N′-dimethyl-N, n′-propylene urea = 1,3-dimmethyl-2-oxohexahydropyrimidine) is shown to exhibit the same effects as HMPT in oxirane-opening with Li-acetylide, in a Wittig olefination, in the double deprotonation of nitroalkane, and in the Michael addition of Li-dithiane to cyclohexenone,.
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(α-Alkylation of α-heterosubstituted carboxylic acids without racemization : EPC-syntheses of tertiary alcohols and thiols☆☆☆
TL;DR: In this paper, α-hydroxy- and α-mercapto-carboxylic acids are condensed with pivalaldehyde to give 2-t-butyl-5-substituted-l, 3-dioxolanones or 1,3-oxathiolanones.
Journal ArticleDOI
Di-tert.-butyldicarbonat — ein vorteilhaftes Reagenz zur Einführung der tert.-Butyloxycarbonyl-Schutzgruppe
Journal ArticleDOI
Alpha-methyl ornithine, a potent competitive inhibitor of ornithine decarboxylase, blocks proliferation of rat hepatoma cells in culture
TL;DR: Findings of hepatoma tissue culture cells support the concept that polyamines play an essential function in the cell division processes by blocking the usual increases of putrescine and spermidine concentrations in these cells.
Journal ArticleDOI
Addition of chiral glycine, methionine, and vinylglycine enolate derivatives to aldehydes and ketones in the preparation of enantiomerically pure α-amino-β-hydroxy acids
TL;DR: Information suggesting that both steric and stereoelectronic effects are responsible for the good stereoselectivities observed is presented, suggesting that the title amino acids are of high enantiomeric purity.
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