Photoelektronentransfer‐induzierte Makrocyclisierung von <i>N</i>‐Phthaloyl‐ω‐aminocarbonsäuren

Griesbeck, Axel G.; Henz, Andreas; Peters, Karl; Peters, E.‐M.

doi:10.1002/ange.19951070415

Cited by 23 publications

(6 citation statements)

References 22 publications

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“…We have recently described the synthesis of medium- and large-sized heterocyclic compounds via decarboxylative intramolecular photocyclization of ω-phthalimido carboxylic acids . An essential prerequisite for this reaction is the use of alkali metal carboxylates, which were prepared in situ or prior to the reaction.…”

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confidence: 99%

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Decarboxylative Photocyclization: Synthesis of Benzopyrrolizidines and Macrocyclic Lactones

1999

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The benzopyrrolizidines 2, 6a, and 6b were synthesized from the enantiomerically pure γ-amino acid derivatives 1, 5a, and 5b by decarboxylative photocyclization of the corresponding potassium salts in aqueous acetone. The diastereoselectivity of the radical coupling step was low (dr ) 60:40) for the N-phthaloylglutamic acid methyl ester 1, whereas the R-benzyl-and the R-methyl-substituted γ-phthalimido butyric acid derivatives 5a,b cyclized with high cis diastereoselectivity (dr ) 91:9 and 97:3, respectively). Acid-catalyzed epimerization of the cis/trans-2 mixture gave exclusively cis-2. The benzopyrrolizidines cis/trans-2 mixture was transformed with high stereoselectivity (dr ) 93:7, ee >98%) into the cis methyl ether 3 via the corresponding acyliminium cation and subsequently into the allyl derivative 4 (dr ) 86:14) with trimethylallylsilane catalyzed by titanium tetrachloride. The structures of the benzopyrrolizidines rac-3, (+)-3, rac-4, and 6a were determined by X-ray structure analyses. The macrocyclic lactones 8a,b were formed in high yields from the precursors 7a,b. The diastereoselectivity for the valine-derived substrate (in contrast to the reactions of 5a and 5b) was only moderate (dr ) 64:36). The structure of the macrolide 9a (from 8a) was determined by X-ray structure analysis.We have recently described the synthesis of mediumand large-sized heterocyclic compounds via decarboxylative intramolecular photocyclization of ω-phthalimido carboxylic acids. 2 An essential prerequisite for this reaction is the use of alkali metal carboxylates, which were prepared in situ or prior to the reaction. The in situ method uses heterogeneous conditions and is superior for base-labile substrates. Many starting materials could be deprotonated prior to photolysis and irradiated in homogeneous solvent mixtures of organic solvents and water. 3

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“…The photocyclization of the glutamic acid derivative 1 has been described previously . After completion of the four-step synthesis, we isolated the methoxy-substituted compound 3 as a racemic mixture (space group P 2 1 / n )…”

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Decarboxylative Photocyclization: Synthesis of Benzopyrrolizidines and Macrocyclic Lactones

1999

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“…[105] Griesbeck and co-workersp erformed important early work demonstrating the intramolecular cyclisation of N-phthaloyl w-aminoa cids under UV irradiation. [106] Substrate 47 is prototypical of this approach-on photoexcitation to generate 48,t he phthalimide chromophore underwentP ET with the terminal carboxylate, generating ak etyl radical anion on the phthalimide,a nd ac arboxyl radical at the end of the chain, 49 (Figure 17 a). Rapid decarboxylation to form ap rimary alkyl radical 50 was followed by subsequentb iradical intersystem crossing (a triplet state to singlet state transition via the spin flip of an electron) and ensuing cyclisation through radical-radical coupling, to give macrocyclica midol 51 in 81 %y ield.…”

Section: Intramolecular Pet-initiated Peptide Macrocyclisationmentioning

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Photochemical Methods for Peptide Macrocyclisation

Raynal

Rose

Donald

et al. 2020

Chemistry A European J

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Photochemical reactions have been the subject of renewed interest over the last two decades, leading to the development of many new,d iversea nd powerful chemical transformations. More recently,t hese developments have been expanded to enable the photochemical macrocyclisation of peptidesa nd small proteins. These constructs benefit from increased stability, structuralr igidity and biological potency over their linear counterparts, providing opportunities for improved therapeutica gents. In this review,a no verview of both the established and emerging methods for photochemicalp eptide macrocyclisation is presented, highlighting both the limitations and opportunities for further innovation in the field.

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“…From these experiments it became obvious that the addition of bases or the direct use ofthe potassium salts in the presence of small amounts of watcr activates the carboxylates as electron donor groups for PET reactions. Consequently, we tried to activate o-amino carboxylates as substrates in order to activate electron donors in remote positions [22]. The pool of chiral enantiomerically pure amino acids offers two candidates: aspartic and glutamic acid.…”

Section: Pet-initiated Decarboxylationmentioning

confidence: 99%

Photochemical Activation of Amino Acids: From the Synthesis of Enantiomerically Pure β,γ‐Unsaturated Amino Acids to Macrocyclic Ring Systems

Griesbeck

1996

Liebigs Ann./Recl.

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Amino acids whose amino groups are transformed into phthalimido chromophores are versatile substrates for photochemical transformations such as cyclization, isomerization, and P-cleavage. These processes are initiated by homolytic or mesolytic CH activation and depend on the spin state of the excited substrate. Derivatives of a-amino acids without strong electron-donating substituents [Abu, Nva, Val, Leu, Ile, Tle, Phe, Met(SO)] react by initial homolytic CH activation and solely via their first excited singlet states, whereas substrates with strong electron-donating substituents (Tyr, DOPA, Met, Glu, Asp) react by initial photoinduced electron transfer (PET) followed by mesolytic CH activation and solely via their first excited triplet states. The S-alkyl cysteine derivatives are the only ones which show competing singlet and triplet state reactivity with pronounced spin-determined regioselective CH activation. The amino dicarboxylic acids Glu and Asp could be applied as the carboxylates in PET reactions, a strategy which also opened up a new synthetic approach to medium-and large-ring systems.

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Photoelektronentransfer‐induzierte Makrocyclisierung von N‐Phthaloyl‐ω‐aminocarbonsäuren

Cited by 23 publications

References 22 publications

Decarboxylative Photocyclization: Synthesis of Benzopyrrolizidines and Macrocyclic Lactones

Decarboxylative Photocyclization: Synthesis of Benzopyrrolizidines and Macrocyclic Lactones

Photochemical Methods for Peptide Macrocyclisation

Photochemical Activation of Amino Acids: From the Synthesis of Enantiomerically Pure β,γ‐Unsaturated Amino Acids to Macrocyclic Ring Systems

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