A simple method for the synthesis of an azepane quaternary amino acid in enantiopure form is described. Theoretical, NMR, and X-ray studies indicated that this azepane-derived amino acid is an effective stabilizer of 3(10) helical structures in short peptides.
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http://dx.doi.org/10.1021/jo301379r | DOI Listing |
J Org Chem
September 2024
University of Rostock, Institute of Chemistry, Albert-Einstein-Str. 3a, Rostock 18059, Germany.
Dihydroazepino[1,2-]indole diones are tricyclic -acyl-2-alkylidene-3-oxindole enones that readily engage in tertiary phosphine-catalyzed intermolecular coupling reactions with acceptor-substituted alkenes. In these reactions, the tricyclic α-substituted enones undergo an α-alkylation with concomitant formation of a quaternary stereocenter, as well as the installation of a new double bond within the seven-membered azepane ring. The organocatalytic reaction constitutes a special case of the crossed intermolecular Rauhut-Currier reaction as the presence of the α-substituent in the enones prohibits the formation of an α,β-unsaturated product, but instead, skipped β,γ-unsaturated enones are obtained.
View Article and Find Full Text PDFChem Asian J
March 2024
Department of Chemistry, National Chung Hsing University, 250 Kuokuang road, Taichung, 402, Taiwan, R.O.C.
A one-pot route to a novel azepane-fused tetrahydro-β-carboline framework from tryptyl-4-pentenamide derivatives has been developed, featuring the Rh-catalyzed hydroformylation double cyclization. Subsequent alkylation in the tetracyclic system proceeded stereoselectively to form a quaternary carbon. The synthesis of (±)-20-epi-kopsiyunnanine K was accomplished through the strategy.
View Article and Find Full Text PDFJ Org Chem
October 2023
Instituto de Química Médica (IQM-CSIC), Juan de la Cierva 3, 28006 Madrid, Spain.
β-Turns are one of the most common secondary structures found in proteins. In the interest of developing novel β-turn inducers, a diastereopure azepane-derived quaternary amino acid has been incorporated into a library of simplified tetrapeptide models in order to assess the effect of the azepane position and peptide sequence on the stabilization of β-turns. The conformational analysis of these peptides by molecular modeling, NMR spectroscopy, and X-ray crystallography showed that this azepane amino acid is an effective β-turn inducer when incorporated at the + 1 position.
View Article and Find Full Text PDFOrg Lett
September 2022
Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States.
The alkylations of chiral seven-membered rings fused to tetrazoles are highly diastereoselective. The diastereoselectivity depended on the placement and the size of the substituent on the ring and on the electrophile. Subsequent alkylations occurred with high stereoselectivity, allowing for the construction of quaternary stereocenters.
View Article and Find Full Text PDFOrg Lett
July 2022
Université de Poitiers, IC2MP, UMR CNRS 7285, Equipe "OrgaSynth", Groupe Glycochimie, 4 rue Michel Brunet, 86073 Poitiers Cedex 9, France.
We report the synthesis of iminosugar ,-glycosides starting from 6-azidoketopyranoses. Their Staudinger-azaWittig-mediated cyclization provided bicyclic ,-acetals, which were stereoselectively opened with AllMgBr to afford β-hydroxyazepanes with a quaternary carbon α to the nitrogen. Their ring contraction via a β-aminoalcohol rearrangement produced the six-membered l-iminosugars with two functional handles at the pseudoanomeric position.
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