EPR/spin trapping study of the spontaneous addition of dioxygen on a dienol

Najjar, Fadia; André-Barrès, Christiane; Lauricella, Robert; Gorrichon, Liliane; Tuccio, Béatrice

doi:10.1016/j.tetlet.2005.01.123

Cited by 27 publications

(24 citation statements)

References 19 publications

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“…Similar systems are known to react with O 2 in a similar manner, xliii,xliv and electron paramagnetic resonance (EPR)/ spin trapping studies support a stepwise radical pathway involving triplet oxygen. xlv Small scale attempts to prevent peroxidation through freeze-pump-thaw degassing were unsuccessful.…”

Section: Resultsmentioning

confidence: 99%

Synthetic studies toward (+)-cortistatin A

2011

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We describe herein the synthesis of a late-stage intermediate en route to cortistatin A. Key transformations included a Snieckus-like cascade sequence culminating in a 6π-electrocyclization, an alkylative dearomatization, and the stereoselective functionalization of the cortistatin A-ring. While the total synthesis we sought was not accomplished, the work sets the stage for several approaches to the preparation of novel analogs via diverted total synthesis.

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Section: Resultsmentioning

confidence: 99%

Synthetic studies toward (+)-cortistatin A

2011

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“…Any discussion of mechanism must be highly speculative, but we can consider the one in Scheme 5 that is analogous to suggestions in the literature. 8,9 Triplet oxygen could undergo a radical addition to C-5 of the oxazole ring to make a resonance-stabilized triplet diradical. Addition at C-2 has less favorable resonance forms.…”

Section: Discussionmentioning

confidence: 99%

“…8 A dienol was found to react with triplet oxygen without catalyst to produce an endoperoxide, and radical intermediates were detected using spin traps. 9 Helianthrene reacted with triplet oxygen to make an endoperoxide by a spin forbidden process. 10 Triplet oxygen reacted with 2-methyl-1-naphthol to make naphthoquinone with good selectivity by direct O 2 addition to the ring.…”

Section: Discussionmentioning

confidence: 99%

An unusual thermal oxidation of triaryloxazoles

Pickett

2015

Tetrahedron Letters

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“…Similar transitions have been found in non‐enzymatic, light‐independent reactions of O 2 addition on enolic compounds, with energy barriers of 87–96 kJ mol −1 (Najjar et al . ; Triquigneaux et al . ; Kholdeeva et al .…”

Section: Most Likely Chemical Events and Energy Profilementioning

confidence: 97%

The mechanism of Rubisco‐catalysed oxygenation

Tcherkez

2015

Plant Cell & Environment

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Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of photosynthetic carbon assimilation because it catalyses the fixation of CO2 onto ribulose-1,5-bisphosphate (RuBP). The enzyme also catalyses RuBP oxygenation, thereby evolving phosphoglycolate which is recycled along the photorespiratory pathway. Oxygenation is quantitatively important, because under ordinary gaseous conditions, more than one third of RuBP molecules are oxygenated rather than carboxylated. However, contrary to carboxylation, the chemical mechanism of oxygenation is not well known, and little progress has been made since the early 80s. Here, I review recent experimental data that provide some new insights into the reaction mechanism, and carry out simple calculations of kinetic parameters. Isotope effects suggest that oxygenation is less likely initiated by a redox phenomenon (such as superoxide production) and more likely involves concerted chemical events that imply interactions with protons. A possible energy profile of the reaction is drawn which suggests that the generation of the oxygenated reaction intermediate (peroxide) is irreversible. Possible changes in oxygenation-associated rate constants between Rubisco forms are discussed.

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EPR/spin trapping study of the spontaneous addition of dioxygen on a dienol

Cited by 27 publications

References 19 publications

Synthetic studies toward (+)-cortistatin A

Synthetic studies toward (+)-cortistatin A

An unusual thermal oxidation of triaryloxazoles

The mechanism of Rubisco‐catalysed oxygenation

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