Enantioselective Preparation of (2R)- and (2S)-Azetidine-2-carboxylic Acids

Wessig, Pablo; Schwarz, Jutta

doi:10.1002/(sici)1522-2675(19981007)81:10<1803::aid-hlca1803>3.0.co;2-4

Cited by 26 publications

(3 citation statements)

References 15 publications

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“…The photoinduced intramolecular γ-hydrogen abstraction process was found to be suitable for the synthesis of nitrogen containing four membered rings, as demonstrated in the preparation of azetidinols. 64 β-lactams were likewise accessible with a good ee (ca. 60%) when a water suspension of a glyoxylamide precursor was irradiated in the presence of a chiral host and hexadecyltrimethylammonium bromide as the surfactant.…”

Section: Four Membered Ringsmentioning

confidence: 99%

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

2016

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The present review offers an overview of the current approaches for the photochemical and photocatalytic generation of reactive intermediates and their application in the formation of carbon-carbon bonds. Valuable synthetic targets are accessible, including arylation processes, formation of both carbo- and heterocycles, alpha- and beta-functionalization of carbonyls, and addition reactions onto double and triple bonds. According to the recent advancements in the field of visible/solar light catalysis, a significant part of the literature reported herein involves radical ions and radicals as key intermediates, with particular attention to the most recent examples. Synthetic application of carbenes, biradicals/radical pairs and carbocations have been also reported.

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Section: Four Membered Ringsmentioning

confidence: 99%

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

2016

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“…Earlier syntheses of racemic 2‐azetidine carboxylic acids by resolution and by a series of transformations starting from homoserine have been reviewed (27–29). Aze analogs have been synthesized bearing substituents at the 1‐ (30–37), 2‐ (38–42), 3‐ (21,43–50), and 4‐positions (51), as well as with multiple substitution patterns (52–55).…”

Section: Introductionmentioning

confidence: 99%

Amino acid–azetidine chimeras: synthesis of enantiopure 3‐substituted azetidine‐2‐carboxylic acids

Sajjadi

Lubell

2005

The Journal of Peptide Research

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Azetidine-2-carboxylic acid (Aze) analogs possessing various heteroatomic side chains at the 3-position have been synthesized by modification of 1-9-(9-phenylfluorenyl) (PhF)-3-allyl-Aze tert-butyl ester (2S,3S)-1. 3-Allyl-Aze 1 was synthesized by regioselective allylation of alpha-tert-butyl beta-methyl N-(PhF)aspartate 13, followed by selective omega-carboxylate reduction, tosylation, and intramolecular N-alkylation. Removal of the PhF group and olefin reduction by hydrogenation followed by Fmoc protection produced nor-leucine-Aze chimera 2. Regioselective olefin hydroboration of (2S,3S)-1 produced primary alcohol 23, which was protected as a silyl ether, hydrogenated and N-protected to give 1-Fmoc-3-hydroxypropyl-Aze 26. Enantiopure (2S,3S)-3-(3-azidopropyl)-1-Fmoc-azetidine-2-carboxylic acid tert-butyl ester 3 was prepared as a Lys-Aze chimera by activation of 3-hydroxypropyl-Aze 26 as a methanesulfonate and displacement with sodium azide. Moreover, orthogonally protected azetidine dicarboxylic acid 4 was synthesized as an alpha-aminoadipate-Aze chimera by oxidation of alcohol 26. These orthogonally protected amino acid-Aze chimeras are designed to serve as tools for studying the influence of conformation on peptide activity.

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“…30 The stereoselective reduction of the ketone 3 via the Felkin-Anh model successfully proceeded with L-selectride, providing synenriched 4a in 86% yield (syn/anti = 89:11). After the tertbutyldimethylsilyl (TBS)-protection of the resulting alcohol in 4a, the methylation of the amino group in 5a using excess amounts of NaH and MeI 31 furnished the N-methylcarbamate 6a. The Boc group in 6a was removed by TMSOTf/2,6lutidine 32,33 without losing acid-labile TBS groups, and the subsequent protection with an Fmoc group gave the Fmoc amine 7a in 97% yield over two steps.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Total Synthesis and Structural Revision of Cyclotetrapeptide Asperterrestide A

et al. 2019

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The structural revision of cyclotetrapeptide asperterrestide A has been achieved based on total synthesis and molecular modeling. For these studies, (2R,3S)-MePhe(3-OH) and (2S,3S)-MePhe(3-OH) suitably protected for peptide synthesis were prepared via a stereoselective reduction of a ketone precursor derived from L- or d-serine, using L-selectride or DIBAL-H. The synthesis of the proposed structure of asperterrestide A (1a) was accomplished by solution-phase synthesis of a linear precursor followed by macrolactamization. The NMR spectra of our synthetic 1a were not identical to those reported for the natural compound. Molecular modeling studies suggested that the correct structure 1b was the one in which the stereochemistry at the α-positions of the Ala and MePhe(3-OH) residues is the opposite to that of the proposed structure. This was confirmed by the total synthesis of 1b and its subsequent structural characterization.

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Enantioselective Preparation of (2R)- and (2S)-Azetidine-2-carboxylic Acids

Cited by 26 publications

References 15 publications

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

Amino acid–azetidine chimeras: synthesis of enantiopure 3‐substituted azetidine‐2‐carboxylic acids

Total Synthesis and Structural Revision of Cyclotetrapeptide Asperterrestide A

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