1H n.m.r. long‐range coupling in 2,4‐disubstituted‐5(4H)‐oxazolones and 4‐alkyl‐5(2H)‐oxazolones generated therefrom by the action of triethylamine

Chen, F. M. F.; Benoiton, N. Leo

doi:10.1111/j.1399-3011.1987.tb03380.x

Cited by 10 publications

(1 citation statement)

References 8 publications

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“…Time shortening did not affect the reaction outcome positively. Then, the DIPEA amount was lowered to one equivalent (amino acid:base = 1:1), whereas the chirality loss of the amino acid is often ascribed to a base-promoted deprotonation of the activated amino acid [ 27 ]. An equimolar amount of DIPEA led, again, to a mixture of 2a diastereoisomers within 24 or 3 h (entries 3 and 4).…”

Section: Resultsmentioning

confidence: 99%

N-Acetyl-l-phenylalanine Racemization during TBTU Amidation: An In-Depth Study for the Synthesis of Anti-Inflammatory 2-(N-Acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA)

et al. 2023

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A thorough study on the amidation conditions of N-acetyl-l-phenylalanine using TBTU and various bases is reported for the synthesis of 2-(N-acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA), a promising drug for the treatment of joints diseases. TBTU-mediated diastereoselective amidation reaction with 1,3,4,6-tetra-O-acetyl-β-d-glucosamine always gave racemization of N-acetyl-l-phenylalanine. The stereochemical retention under amidation conditions was studied in detail in the presence of difference bases and via other control experiments, evidencing the possibility to reduce racemization using pyridine as base.

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Section: Resultsmentioning

confidence: 99%

N-Acetyl-l-phenylalanine Racemization during TBTU Amidation: An In-Depth Study for the Synthesis of Anti-Inflammatory 2-(N-Acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA)

et al. 2023

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A new method proposed for the determination of absolute configurations of α‐amino acids

Gómez

Duddeck

2009

Magnetic Reson in Chemistry

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Enantiopure alpha-amino acids were converted to 4-substituted 2-aryl- and 2-alkyl-5(4H)-oxazolones under partial racemization. These nonracemic mixtures were dissolved in CDCl(3), an equimolar amount of the chiral dirhodium complex Rh(II)(2)[(R)-(+)-MTPA](4) (MTPA-H = Mosher's acid) was added, and the (1)H NMR spectra of the resulting samples were recorded (dirhodium method). The relative intensities of (1)H signals dispersed by the formation of diastereomeric adducts allow to determine the absolute configuration (AC) of the starting alpha-amino acids. Binding atoms in the adducts were identified by comparing the (1)H and (13)C chemical shifts of the oxazolones in the absence and presence of Rh(II)(2)[(R)-(+)-MTPA](4). Thereby, information about the scope and limits of this method can be extracted. A protocol how to use this method is presented.

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Ring opening with kinetic resolution of azlactones by Ti-TADDOLates

Gottwald¹,

Seebàch²

1999

Tetrahedron

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¹H n.m.r. long‐range coupling in 2,4‐disubstituted‐5(4H)‐oxazolones and 4‐alkyl‐5(2H)‐oxazolones generated therefrom by the action of triethylamine

Cited by 10 publications

References 8 publications

N-Acetyl-l-phenylalanine Racemization during TBTU Amidation: An In-Depth Study for the Synthesis of Anti-Inflammatory 2-(N-Acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA)

N-Acetyl-l-phenylalanine Racemization during TBTU Amidation: An In-Depth Study for the Synthesis of Anti-Inflammatory 2-(N-Acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA)

A new method proposed for the determination of absolute configurations of α‐amino acids

Ring opening with kinetic resolution of azlactones by Ti-TADDOLates

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