Asymmetric transfer hydrogenation of α,β-unsaturated, α-tosyloxy and α-substituted ketones

Peach, Philip; Cross, David J.; Kenny, Jennifer A.; Mann, Ian; Houson, Ian; Campbell, Lynne; Walsgrove, Tim; Wills, Martin

doi:10.1016/j.tet.2005.11.036

Cited by 97 publications

(29 citation statements)

References 71 publications

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“…(19). Meanwhile, the product of TpdAB showed three peaks with ␦ 8.67 (s, 1H, NH), 1.88 (s, 3H, CH 3 ), and 1.82 (s, 3H, CH 3 ), while the 13 C NMR spectrum contained four peaks with ␦ 167.7, 121.2, 23.2, and 16.4.…”

Section: Resultsmentioning

confidence: 96%

Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

Kutanovas

Stankevičiūtė

Urbelis

et al. 2013

Appl Environ Microbiol

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bAt present, there are no published data on catabolic pathways of N-heterocyclic compounds, in which all carbon atoms carry a substituent. We identified the genetic locus and characterized key reactions in the aerobic degradation of tetramethylpyrazine in Rhodococcus jostii strain TMP1. By comparing protein expression profiles, we identified a tetramethylpyrazine-inducible protein of 40 kDa and determined its identity by tandem mass spectrometry (MS-MS) de novo sequencing. Searches against an R. jostii TMP1 genome database allowed the identification of the tetramethylpyrazine-inducible protein-coding gene. The tetramethylpyrazine-inducible gene was located within a 13-kb genome cluster, denominated the tetramethylpyrazine degradation (tpd) locus, that encoded eight proteins involved in tetramethylpyrazine catabolism. The genes from this cluster were cloned and transferred into tetramethylpyrazine-nondegrading Rhodococcus erythropolis strain SQ1. This allowed us to verify the function of the tpd locus, to isolate intermediate metabolites, and to reconstruct the catabolic pathway of tetramethylpyrazine. We report that the degradation of tetramethylpyrazine is a multistep process that includes initial oxidative aromatic-ring cleavage by tetramethylpyrazine oxygenase, TpdAB; subsequent hydrolysis by (Z)-N,N=-(but-2-ene-2,3-diyl)diacetamide hydrolase, TpdC; and further intermediate metabolite reduction by aminoalcohol dehydrogenase, TpdE. Thus, the genes responsible for bacterial degradation of pyrazines have been identified, and intermediate metabolites of tetramethylpyrazine degradation have been isolated for the first time. P yrazines, monocyclic aromatic rings with two nitrogen atoms in para position, are a class of compounds that occur almost ubiquitously in nature. Various pyrazines can be synthesized both chemically and biologically, including tetramethylpyrazine (TTMP), which is produced by different bacteria (1, 2) or plants (3, 4). However, there is very little information available on the biodegradation of these N-heterocyclic compounds. While bacterial strains able to use various alkyl-substituted pyrazines as a sole carbon and energy source have been isolated and described (5-9), almost nothing is known about the degradation pathways of alkylpyrazines, including tetramethylpyrazine, in which all carbon atoms carry a substituent.Under aerobic conditions, alkylated pyrazines are metabolized via oxidative degradation, leading to the hydroxylation of the ring at a free position. Rhodococcus erythropolis DSM 6138 and Arthrobacter sp. strain DSM 6137 can use 2,5-dimethylpyrazine as a source of carbon and energy. The catabolism of 2,5-dimethylpyrazine by these microorganisms gives rise to the intermediate metabolite 2-hydroxy-3,6-dimethylpyrazine, which accumulates in the medium, indicating that ring hydroxylation occurs during the initial steps of degradation (5). However, no enzymes involved in this bioconversion were reported in the patent that describes the aforementioned reactions (5).The 2,5-dimethylpyraz...

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Section: Resultsmentioning

confidence: 96%

Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

Kutanovas

Stankevičiūtė

Urbelis

et al. 2013

Appl Environ Microbiol

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“…To showcase the broader utility of the catalytic system, we also applied C4 to the reduction of keto esters 6a. d, i, 19 Both aromatic and aliphatic β‐keto esters were reduced to afford the corresponding alcohols with excellent yields under the catalysis of 0.1 mol % of C4 (Table 4). Likewise, the analogous α‐keto esters were also reduced with ease, which demonstrates the versatility of the cyclometalated iridium catalyst.…”

Section: Resultsmentioning

confidence: 99%

Versatile Iridicycle Catalysts for Highly Efficient and Chemoselective Transfer Hydrogenation of Carbonyl Compounds in Water

Talwar

Saidi

et al. 2014

Chemistry A European J

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Cyclometalated iridium complexes are shown to be highly efficient and chemoselective catalysts for the transfer hydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α-substituted ketones (α-ether, α-halo, α-hydroxy, α-amino, α-nitrile or α-ester), α-keto esters, β-keto esters and α,β-unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of up to 50 000 at pH 4.5 and required no organic solvent. The protocol provides a practical, easy and efficient way for the synthesis of β-functionalised secondary alcohols, such as β-hydroxyethers, β-hydroxyamines and β-hydroxyhalo compounds, which are valuable intermediates in pharmaceutical, fine chemical, perfume and agrochemical synthesis.

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“…Compounds 12e and 12f by aldol condensation of benzaldehyde with 3-methylbutan-2-one and pinacolone have been prepared previously in lower yields (58 and 50 %, respectively, compared with 72 and 64 %, entries 5 and 6). [27] In the reactions involving conjugated anhydrides, no decarbonylative coupling was detected (entries 7-10). Also, despite the sensitivity of the acylation catalyst towards halide anions, no deactivation of the rhodium species was observed by introducing various functional and heteroaryl groups (free hydroxy, thiophene, isoxazole, pyrazine and ester functions).…”

Section: Resultsmentioning

confidence: 99%

Sequential Hiyama Coupling/Narasaka Acylation Reaction of (E)‐1,2‐Disilylethene: Rapid Assembly of α,β‐Unsaturated Carbonyl Motifs

Thiot¹,

Mioskowski²,

Wagner³

2009

Eur J Org Chem

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The synthesis and application of (E)‐1,2‐disilylethene 5 as a central functional building block in a sequential Hiyama coupling/Narasaka acylation reaction are described. Its use in the rapid and versatile construction of α,β‐unsaturated carbonyl motifs found in a number of polyunsaturated natural products has been demonstrated. It was observed that due to the differential intrinsic reactivity of the two carbon–silicon bonds, this bis‐metallated lynchpin‐type reagent is activated selectively and sequentially by Pd and Rh catalysis, negating the need for any protecting group. A number of (E)‐α,β‐unsaturated ketones were efficiently synthesized with complete chemoselectively in the presence of a variety of halides and anhydride acids. Conjugated polyunsaturated ketones and diversely α′‐functionalized α,β‐enones, such as chalcones, a heterocyclic dienone and the highly conjugated ethyl (2Z,4E)‐6‐oxo‐6‐(2‐thienyl)hexa‐2,4‐dienoate, were obtained in good overall yields. Thus, this coupling sequence provides a high degree of modularity, that is, a single template is likely to produce a large number of synthetic targets.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Asymmetric transfer hydrogenation of α,β-unsaturated, α-tosyloxy and α-substituted ketones

Cited by 97 publications

References 71 publications

Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

Versatile Iridicycle Catalysts for Highly Efficient and Chemoselective Transfer Hydrogenation of Carbonyl Compounds in Water

Sequential Hiyama Coupling/Narasaka Acylation Reaction of (E)‐1,2‐Disilylethene: Rapid Assembly of α,β‐Unsaturated Carbonyl Motifs

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