Synthesis of Substituted Oxazoles from <i>N</i>‐Acyl‐β‐hydroxyamino Acid Derivatives

Ferreira, Paula M. T.; Monteiro, Luís S.; Pereira, Goreti

doi:10.1002/ejoc.200800602

Cited by 37 publications

(20 citation statements)

References 21 publications

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“…Although asymmetric hydrogenation is often the state-of-art method for the preparation of chiral α-amino acids (6), it remains practically challenging to access a structurally diverse collection of β-Ar-β-Ar'-α-amino acids in this way due to the difficulties associated with synthesis of the requisite enamide starting materials with defined alkene stereochemistry (Fig. 1A) (7). …”

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confidence: 99%

Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Li²,

Deng³

et al. 2014

Science

481

252

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The development of ligands that can promote selective insertion of a metal into primary or secondary C(sp3)–H bonds is a central challenge in the field of C–H functionalization. Here, we report a rare example of catalyst-controlled primary and secondary C(sp3)–H arylation using two different ligands. Successive application of these ligands enables the sequential hetero-diarylation of an alanine derivative with two different aryl iodides affording a wide range of β-Ar-β-Ar'-α-amino acids with excellent levels of diastereoselectivity (d.r. > 20:1). Both configurations of the β-chiral center can be accessed by choosing the order in which the aryl iodides are installed, thus demonstrating the potential to construct tertiary chiral centers from a simple methyl group. The realization of this reactivity by electronic and steric modulation of the ligands may provide fundamental guidance for the future design of more effective and selective catalysts for C(sp3)–H activation.

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confidence: 99%

Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Li²,

Deng³

et al. 2014

Science

481

252

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“…To evaluate the influence of other N-protecting groups namely acyl protecting groups, the methyl esters of N-benzoyl-β-bromodehydroaminobutyric acid (Z-3 and E-3) (Ferreira et al 2010b) were reacted with benzamide (Scheme 2). The coupled product E-2f [(E)-methyl 2,3bis(benzamido)but-2-enoate] was isolated in 38 % yield together with the trisubstituted oxazole 4 (Ferreira et al 2008) (58 % yield) using E-3 as substrate. When Z-3 was reacted with benzamide the only products isolated were the corresponding oxazole 4 (Ferreira et al 2008) (37 % yield) together with the methyl ester of Nbenzoyldehydroaminobutyric acid (5).…”

Section: Resultsmentioning

confidence: 99%

“…The coupled product E-2f [(E)-methyl 2,3bis(benzamido)but-2-enoate] was isolated in 38 % yield together with the trisubstituted oxazole 4 (Ferreira et al 2008) (58 % yield) using E-3 as substrate. When Z-3 was reacted with benzamide the only products isolated were the corresponding oxazole 4 (Ferreira et al 2008) (37 % yield) together with the methyl ester of Nbenzoyldehydroaminobutyric acid (5). These results were expected since recently it was developed in our laboratories a new method for the synthesis of oxazoles from N-acyl-β-bromodehydroaminobutyric acid derivatives by treatment with base.…”

Section: Resultsmentioning

confidence: 99%

“…1 H NMR (400 MHz, CDCl 3 ): 2.64 (s, 3 H, γCH 3 ), 3.79 (s, 3 H, OCH 3 ), 7.11 (br s, 1 H, αNH), 7.44-7.61 (m, 6 H, ArH), 7.90 (m, 2 H, ArH), 8.01 (d, J = 7.6 Hz , 2 H, ArH), 12.47 (br s, 1 H, NH) ppm. 13 The general procedure described above was followed with compound Z-3 (0.5 mmol, 149 mg) to give after column chromatography using diethyl ether/petroleum ether compound 4 (40 mg, 37%) together with Bz-∆Abu-OMe 5 (Ferreira et al 2008).…”

Section: Synthesismentioning

confidence: 99%

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Synthesis of new β-amidodehydroaminobutyric acid derivatives and of new tyrosine derivatives using copper catalyzed C–N and C–O coupling reactions

2012

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Several β-amidodehydroaminobutyric acid derivatives were prepared from N,C-diprotected β-bromodehydroaminobutyric acids and amides by a copper catalyzed C-N coupling reaction. The best reaction conditions include the use of a catalytic amount of CuI, N,N'-dimethylethylenediamine as ligand and K(2)CO(3) as base in toluene at 110 °C. The stereochemistry of the products was determined using NOE difference experiments and the results obtained are in agreement with an E-stereochemistry. Thus, the stereochemistry is maintained in the case of the E-isomers of β-bromodehydroaminobutyric acid derivatives, but when the Z-isomers were used as substrates the reaction proceeds with inversion of configuration. The use of β-bromodehydrodipeptides as substrates was also tested. It was found that the reaction outcome depend on the stereochemistry of the β-bromodehydrodipeptide and on the nature of the first amino acid residue. The products isolated were the β-amidodehydrodipeptide derivatives and/or the corresponding dihydropyrazines. The same catalytic system (CuI/N,N'-dimethylethylene diamine) was used in the C-O coupling reactions between a tyrosine derivative and aryl bromides. The new O-aryltyrosine derivatives were isolated in moderate to good yields. The photophysical properties of two of these compounds were studied in four solvents of different polarity. The results show that these compounds after deprotection can be used as fluorescence markers.

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“…Methyl Esters of N ‐Protected β ‐Hydroxy Amino Acids: Z(NO 2 )‐ L ‐Ser‐OMe,17 Z‐ L ‐Ser‐OMe,17 Boc‐ L ‐Ser‐OMe,17 2‐Fur‐ L ‐Ser‐OMe,21 Bz(4‐OMe)‐ L ‐Ser‐OMe,21 Z(NO 2 )‐ L ‐Thr‐OMe,17 Z‐ L ‐Thr‐OMe,17 Boc‐ L ‐Thr‐OMe,17 Nosyl‐ L ‐Thr‐OMe,19 Tos‐ L ‐Thr‐OMe,17 Z(NO 2 )‐ D , L ‐Phe(β‐OH)‐OMe,17 Boc‐ D , L ‐Phe(β‐OH)‐OMe,22 Nosyl‐ D , L ‐Phe(β‐OH)‐OMe,19 Tos‐ D , L ‐Phe(β‐OH)‐OMe;18 the synthesis of these compounds has been described previously.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of New N‐Ethyl Dehydroamino Acid Derivatives: N‐Ethyl β,β‐Dibromo, N‐Ethyl β‐Bromo β‐Substituted, and N‐Ethyl β,β‐Disubstituted N‐Protected Dehydroamino Acid Methyl Esters

2011

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Recently, we reported the use of a sequence of alkylation and dehydration methodologies to obtain new non‐proteinogenic amino acids (N‐ethyl α,β‐dehydroamino acids) from the methyl esters of N‐(4‐nitrophenylsulfonyl) β‐hydroxy amino acids. Thus, it was possible to obtain for the first time, non‐natural amino acids that incorporate both N‐ethyl and α,β‐dehydro moieties. Herein, we report the application of this N‐alkylation procedure to several methyl esters of β,β‐dibromo and β‐bromo β‐substituted dehydroamino acids protected with standard amine protecting groups such as tert‐butyloxycarbonyl, benzyloxycarbonyl, and (4‐nitrobenzyl)oxycarbonyl, as well as acyl and sulfonyl groups. The procedure allows the synthesis of the methyl esters of N‐protected N‐ethyl β,β‐dibromo and N‐ethyl β‐bromo β‐substituted dehydroamino acids in fair to high yields. Some of these N‐ethylated dehydroamino acid derivatives were used as substrates in cross‐coupling reactions to give β,β‐disubstituted N‐ethyldehydroalanine derivatives.

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Synthesis of Substituted Oxazoles from N‐Acyl‐β‐hydroxyamino Acid Derivatives

Cited by 37 publications

References 21 publications

Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Synthesis of new β-amidodehydroaminobutyric acid derivatives and of new tyrosine derivatives using copper catalyzed C–N and C–O coupling reactions

Synthesis of New N‐Ethyl Dehydroamino Acid Derivatives: N‐Ethyl β,β‐Dibromo, N‐Ethyl β‐Bromo β‐Substituted, and N‐Ethyl β,β‐Disubstituted N‐Protected Dehydroamino Acid Methyl Esters

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Synthesis of Substituted Oxazoles from N‐Acyl‐β‐hydroxyamino Acid Derivatives

Cited by 37 publications

References 21 publications

Ligand-Controlled C(sp 3 )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Ligand-Controlled C(sp 3 )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Synthesis of new β-amidodehydroaminobutyric acid derivatives and of new tyrosine derivatives using copper catalyzed C–N and C–O coupling reactions

Synthesis of New N‐Ethyl Dehydroamino Acid Derivatives: N‐Ethyl β,β‐Dibromo, N‐Ethyl β‐Bromo β‐Substituted, and N‐Ethyl β,β‐Disubstituted N‐Protected Dehydroamino Acid Methyl Esters

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Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids

Ligand-Controlled C(sp ³ )–H Arylation and Olefination in Synthesis of Unnatural Chiral α–Amino Acids