5-Endo-Trig Radical Cyclizations

Ishibashi, Hiroyuki; Sato, T.; Ikeda, Masazumi

doi:10.1055/s-2002-25759

Cited by 104 publications

(42 citation statements)

References 33 publications

(36 reference statements)

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“…Possibilities for the CarC-catalyzed epimerization/desaturation process. The proposed 5-endo trig (or 4-exo trig) radical cyclizations in a and b have synthetic precedent (50), including an imine substrate (51). Note the possible intermediacy of datively stabilized radicals.…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure of Carbapenem Synthase (CarC)

Clifton¹,

Doan²,

Sleeman³

et al. 2003

Journal of Biological Chemistry

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The proposed biosynthetic pathway to the carbapenem antibiotics proceeds via epimerization/desaturation of a carbapenam in an unusual process catalyzed by an iron-and 2-oxoglutarate-dependent oxygenase, CarC. Crystal structures of CarC complexed with Fe(II) and 2-oxoglutarate reveal it to be hexameric (space group C222 1 ), consistent with solution studies. CarC monomers contain a double-stranded ␤-helix core that supports ligands binding a single Fe(II) to which 2-oxoglutarate complexes in a bi-dentate manner. A structure was obtained with L-N-acetylproline acting as a substrate analogue. Quantum mechanical/molecular mechanical modeling studies with stereoisomers of carbapenams and carbapenems were used to investigate substrate binding. The combined work will stimulate further mechanistic studies and aid in the engineering of carbapenem biosynthesis.

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Section: Resultsmentioning

confidence: 99%

Crystal Structure of Carbapenem Synthase (CarC)

Clifton¹,

Doan²,

Sleeman³

et al. 2003

Journal of Biological Chemistry

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“…(The low recovery of starting material may be attributed to the formation of oligomers and/or polymers). In contrast, the reaction of O-allyl phenylphosphinothioate (12) with triethylborane (under the same conditions) gave the oxaphospholane 17 in 40 % yield -the formation of 17 is explained by 5-endo-trig cyclisation [14] of the phosphorus-centred radical 15 to give 16. These results are explained by considering how the P-H BDEs of 11 and 12 affects the two hydrogen-atom abstraction steps leading to the oxaphospholane products.…”

Section: Comparing the Reactivity Of Different Phosphorus Hydrides Inmentioning

confidence: 99%

Radical Addition Reactions of Phosphorus Hydrides: Tuning the Reactivity of Phosphorus Hydrides, the Use of Microwaves and Horner–Wadsworth–Emmons‐Type Reactions

et al. 2006

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The reactivity of phosphorus hydrides in radical addition reactions are compared, and the substituents on phosphorus are shown to affect the efficiency of the reactions. The change in reactivity is attributed to the different bond dissociation energies of the P–H bonds, which have been calculated. Phosphorus hydrides with particularly weak P–H bonds are shown to undergo radical additions by microwave irradiation, in the absence of conventional initiators. These radical addition reactions produce phosphonothioates, phosphinothioates and phosphane sulfides, which react in HWE‐type reactions, to afford substituted alkenes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…9 We have found, however, that 5-endo-trig radical cyclizations occurred smoothly in some N-vinylic α-haloacetamides. 10 We turned our attention to enamide 18, which was prepared by trichloroacetylation of imine from 2,2-bis(phenylthio)acetaldehyde and benzylamine.…”

Section: Methodsmentioning

confidence: 87%

Role of 1,4-dimethylpiperazine in radical cyclizations

Taniguchi¹,

Kawajiri²,

Ishibashi³

2008

Arkivoc

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Radical cyclization of o-ethenyltrichloroacetanilides in boiling 1,4-dimethylpiperazine was examined with a comparison of the mode of radical cyclizations under a Bu 3 SnH-mediated condition. It was found that an attack of a hydrogen atom on the cyclized radical intermediates occurred more rapidly in 1,4-dimethylpiperazine than under the Bu 3 SnH-mediated condition. This phenomenon was also observed in similar reactions of N-ethenyltrichloroacetamide.

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5-Endo-Trig Radical Cyclizations

Cited by 104 publications

References 33 publications

Crystal Structure of Carbapenem Synthase (CarC)

Crystal Structure of Carbapenem Synthase (CarC)

Radical Addition Reactions of Phosphorus Hydrides: Tuning the Reactivity of Phosphorus Hydrides, the Use of Microwaves and Horner–Wadsworth–Emmons‐Type Reactions

Role of 1,4-dimethylpiperazine in radical cyclizations

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