Asymmetric synthesis of quaternary α-amino acids using d-ribonolactone acetonide as chiral auxiliary

Moreno‐Mañas, Marcial; Trepat, Elisenda; Sebastián, Rosa Marı́a; Vallribera, Adelina

doi:10.1016/s0957-4166(99)00457-7

Cited by 24 publications

(3 citation statements)

References 30 publications

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“…Further transformations on the acetyl group and on the primary ester permitted the preparation of optically pure α,α-disubstituted glycines. [25,26] We therefore undertook an exploration of the conjugate additions of 1h under ruthenium catalysis and triphenylphosphane catalysis conditions (Table 4 and Scheme 5). Even though the des were moderate or low, the reactivity of 1h is remarkable in terms of chemical yields and broad range of electrophiles.…”

Section: Resultsmentioning

confidence: 99%

The Contribution Made by Triphenylphosphane in the Putative Catalysis by Ruthenium Species in Conjugate Additions of β-Dicarbonyl Compounds

et al. 2001

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Section: Resultsmentioning

confidence: 99%

The Contribution Made by Triphenylphosphane in the Putative Catalysis by Ruthenium Species in Conjugate Additions of β-Dicarbonyl Compounds

et al. 2001

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“…Reduction of the nitro group of (R/S)-10 using tin(II) chloride in refluxing ethanol [58] afforded amines (R/S)-11, which were diazotized with sodium nitrite in sulfuric acid [59] to produce phenols (R/S)-12. Finally, prolonged heating in hydrochloric acid [60] provided the fully deprotected compounds 5-iodo-TIC(OH) ((R/S)-14) or esters (R/S)-13 after an additional Fischer esterification step. The preparation of the TIC(OH) derivatives iodinated at positions 6 and 8 ((R/S)-18 and (R/S)-21, respectively) is outlined in Scheme 3.…”

Section: Chemistrymentioning

confidence: 99%

A Convenient Route to New (Radio)Fluorinated and (Radio)Iodinated Cyclic Tyrosine Analogs

et al. 2022

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The use of radiolabeled non-natural amino acids can provide high contrast SPECT/PET metabolic imaging of solid tumors. Among them, radiohalogenated tyrosine analogs (i.e., [123I]IMT, [18F]FET, [18F]FDOPA, [123I]8-iodo-L-TIC(OH), etc.) are of particular interest. While radioiodinated derivatives, such as [123I]IMT, are easily available via electrophilic aromatic substitutions, the production of radiofluorinated aryl tyrosine analogs was a long-standing challenge for radiochemists before the development of innovative radiofluorination processes using arylboronate, arylstannane or iodoniums salts as precursors. Surprisingly, despite these methodological advances, no radiofluorinated analogs have been reported for [123I]8-iodo-L-TIC(OH), a very promising radiotracer for SPECT imaging of prostatic tumors. This work describes a convenient synthetic pathway to obtain new radioiodinated and radiofluorinated derivatives of TIC(OH), as well as their non-radiolabeled counterparts. Using organotin compounds as key intermediates, [125I]5-iodo-L-TIC(OH), [125I]6-iodo-L-TIC(OH) and [125I]8-iodo-L-TIC(OH) were efficiently prepared with good radiochemical yield (RCY, 51–78%), high radiochemical purity (RCP, >98%), molar activity (Am, >1.5–2.9 GBq/µmol) and enantiomeric excess (e.e. >99%). The corresponding [18F]fluoro-L-TIC(OH) derivatives were also successfully obtained by radiofluorination of the organotin precursors in the presence of tetrakis(pyridine)copper(II) triflate and nucleophilic [18F]F− with 19–28% RCY d.c., high RCP (>98.9%), Am (20–107 GBq/µmol) and e.e. (>99%).

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“…Chiral auxiliaries are preferentially prepared from readily available and inexpensive natural products because a stoichiometric amount of chiral template is required in asymmetric reactions. Since a practical chiral auxiliary using D-ribose as a chiral source was reported in 1977 [18], a wide variety of monosaccharidebased chiral auxiliaries have been reported for asymmetric reactions, including Strecker-and Mannich-type reactions [19][20][21], 1,4-conjugate additions [22][23][24], alkylations [25][26][27], cyclopropanations [28,29], Diels-Alder cycloadditions [30][31][32][33], aza-FriedelCrafts reactions [34], 1,3-dipolar cycloadditions [35][36][37], and many others [38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of polysaccharide derivatives bearing bromobenzoate pendants for use as chiral auxiliaries

Ikai

Kimura

Maeda

et al. 2014

Reactive and Functional Polymers

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Asymmetric synthesis of quaternary α-amino acids using d-ribonolactone acetonide as chiral auxiliary

Cited by 24 publications

References 30 publications

The Contribution Made by Triphenylphosphane in the Putative Catalysis by Ruthenium Species in Conjugate Additions of β-Dicarbonyl Compounds

The Contribution Made by Triphenylphosphane in the Putative Catalysis by Ruthenium Species in Conjugate Additions of β-Dicarbonyl Compounds

A Convenient Route to New (Radio)Fluorinated and (Radio)Iodinated Cyclic Tyrosine Analogs

Synthesis of polysaccharide derivatives bearing bromobenzoate pendants for use as chiral auxiliaries

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