Generation and reactivity of aminyl and aminylium radicals

Lockhart, Robert W.; Snyder, Rodney W.; Chow, Yuan L.

doi:10.1039/c3976000052a

Cited by 11 publications

(8 citation statements)

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“…A number of intramolecular photoreductions of ketoamines are characterized by their insensitivities to triplet quenchers (e.g., dienes) and low quantum yields as opposed to high product yields. The nature of these reactions strongly supports the intermediacy of a fast Intramolecular charge-transfer interaction process (eq 76-78).299-301 -Ar2C-0-CHR'NR2 (72) pounds (eq 70 and 71) or coupling with the intermediate radicals (eq 72). 288 The overall reaction is the oxidation of amines to alkylidenimines balanced by reduction of carbonyl compounds to plnacols (or hydrols).…”

Section: G Other Reactionsmentioning

confidence: 77%

Nonaromatic aminium radicals

Chow¹,

Danen²,

Nelsen³

et al. 1978

Chem. Rev.

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243

151

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Section: G Other Reactionsmentioning

confidence: 77%

Nonaromatic aminium radicals

Chow¹,

Danen²,

Nelsen³

et al. 1978

Chem. Rev.

Self Cite

243

151

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“…It was already demonstrated that one equivalent of NADPH was required to effect anaerobic denitration of one molecule of RDX by the XplB-XplA system (5), but the exact mechanism of electron transfer in the case of XplA remains to be elucidated. Single electron transfer mechanisms have also been established for cyt-P450 acting on a number of substrates (36) and implicated in the abiotic photolytic denitration of, for example, N-nitro-piperidine (37). Given a possible oxygen-independent electron transfer hypothesis as a basis for denitration of RDX, it would not be necessary to consider the structural determinants of a mechanism, which would include, for example, base-catalyzed elimination of HNO 2 , which is known to occur for nitramines under basic conditions (38); nor is it necessary to consider the positioning of the RDX ligand for C-H hydroxylation, because the denitration is known to be catalyzed in an anaerobic environment.…”

Section: Structure Of Xpla-hemementioning

confidence: 99%

The 1.5-Å Structure of XplA-heme, an Unusual Cytochrome P450 Heme Domain That Catalyzes Reductive Biotransformation of Royal Demolition Explosive

Sabbadin

Jackson

Haider

et al. 2009

Journal of Biological Chemistry

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XplA is a cytochrome P450 of unique structural organization, consisting of a heme-domain that is C-terminally fused to its native flavodoxin redox partner. XplA, along with flavodoxin reductase XplB, has been shown to catalyze the breakdown of the nitramine explosive and pollutant hexahydro-1,3,5-trinitro-1,3,5-triazine (royal demolition explosive) by reductive denitration. The structure of the heme domain of XplA (XplA-heme) has been solved in two crystal forms: as a dimer in space group P2 1 to a resolution of 1.9 Å and as a monomer in space group P2 1 2 1 2 to a resolution of 1.5 Å , with the ligand imidazole bound at the heme iron. Although it shares the overall fold of cytochromes P450 of known structure, XplA-heme is unusual in that the kinked I-helix that traverses the distal face of the heme is broken by Met-394 and Ala-395 in place of the well conserved Asp/Glu plus Thr/Ser, important in oxidative P450s for the scission of the dioxygen bond prior to substrate oxygenation. The heme environment of XplA-heme is hydrophobic, featuring a cluster of three methionines above the heme, including Met-394. Imidazole was observed bound to the heme iron and is in close proximity to the side chain of Gln-438, which is situated over the distal face of the heme. Imidazole is also hydrogenbonded to a water molecule that sits in place of the threonine side-chain hydroxyl exemplified by Thr-252 in Cyt-P450cam. Both Gln-438 3 Ala and Ala-395 3 Thr mutants of XplA-heme displayed markedly reduced activity compared with the wild type for royal demolition explosive degradation when combined with surrogate electron donors. Royal demolition explosive (RDX)2 or cyclotrimethylenetrinitramine 1 (see Fig. 1) is a widely used explosive compound with both military and civil applications. The extensive global usage of RDX has resulted in concerns over environmental contamination, because it is both recalcitrant to degradation, leading to contamination in soil and ground water, and a potent convulsant and possible carcinogen. The bioremediation of RDX has thus been the focus of increasing research in recent years, with a number of bacterial strains reported to catalyze its degradation (1-3). Among these, Bruce and co-workers, using a selective enrichment technique, isolated Rhodococcus rhodochrous strain 11Y from an RDX-contaminated site, which was able to grow on RDX as the sole nitrogen source (4). The products of biotransformation of RDX by this bacterium were shown to be nitrite and formaldehyde. A gene cluster in strain 11Y essential for RDX degradation was identified and shown to contain a novel cytochrome P450, termed XplA, and a redox partner, XplB, which were shown together to be capable of catalyzing the biotransformation of RDX in vitro (5). Near identical xplA and xplB genes have now been identified in strains within the Actinomycetales isolated from geographically distinct sites (6). Interestingly, these genes have been found to be plasmid encoded providing compelling evidence for recent lateral gene transfer. In the intere...

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“…Both photolyses of TMT under neutral conditions and TMT-H+ under acidic conditions are not quenched by oxygen, which finds similarity in photolysis of TV-nitroso-29 and TVnitroamines. 25 This suggests that the dissociations of photoexcited TMT or TMT-H+ are very fast and probably faster than bimolecular collisions with oxygen molecules in the solution. All of these photolyses are excellent methods to generate aminium radicals and good synthetic methods for /3-amino alcohols.…”

Section: Discussionmentioning

confidence: 99%

“…By a peak matching technique, the 37min peak was identified as the trans alcohol 10 and the 12-min peak as 9. 9 was separated by preparative VPC as an oil: IR 3020, 2828, 2779 (s), 1688 (w), 1458 (s), 1264, 1177, 1154, 1043, 1032, 994, and 727 (s) cm-1; mass spectrum m.e (rel intensity) 153 (M+, 25), 138…”

Section: Methodsmentioning

confidence: 99%

“…It is interesting to note that the average photon consumption per molecule of halomethane reacted (2100-8000) is far in excess of the [25][26][27][28][29][30][31][32][33][34][35] photons per molecule required for dissociation on thermochemical grounds. This disparity may be explained through the absorption of photons by many molecules in the focal region with only a few of these achieving sufficient energy to dissociate.…”

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confidence: 99%

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