- Alloxazinium-Resins as Readily Available and Reusable Oxidation Catalysts
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N5-Modified alloxazinium salts including 5-ethyl-1,3-dimethylalloxazinium and 5-ethyl-1,3-dimethyl-8-(trifluoromethyl)- A lloxazinium salts were readily prepared as alloxazinium-resins from the corresponding N5-unmodified ingredients via the aerobic oxidationion exchange protocol, previously introduced by us for the preparation of isoalloxazine analogues, and their catalysis and reusability in H2O2 oxidations were evaluated.
- Arakawa, Yukihiro,Imada, Yasushi,Kawahara, Takayuki,Minagawa, Keiji
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supporting information
p. 1728 - 1730
(2021/07/19)
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- Greener Preparation of 5-Ethyl-4a-hydroxyisoalloxazine and Its Use for Catalytic Aerobic Oxygenations
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Isoalloxazine ring systems are found in flavin cofactors in nature, and the simulation of their redox catalyses is an important task for developing sustainable catalytic oxidation reactions. Although 5-ethyl-4a-hydroxyisoalloxazines are among the most promising candidates as catalyst for such purposes, the use of them for laboratorial as well as industrial synthetic chemistry has so far been quite limited presumably due to the lack of their preparation methods readily, safely, and inexpensively available. In this communication, we introduce an environmentally benign and practical preparation of 5-ethyl-4a-hydroxy-3,7,8,10-tetramethylisoalloxazine (1EtOH) from 3,7,8,10-tetramethylisoalloxazine (1), in which conventional synthetic requirements, including (i) operations under inert conditions, (ii) risky or expensive chemicals, and (iii) isolation of labile intermediates, have all been dissolved. In addition, we have presented that 1EtOH could be an effective catalyst for Baeyer–Villiger oxidation as well as sulfoxidation with molecular oxygen (O2) as a terminal oxidant under suitable conditions, which is the first report on aerobic oxygenations catalyzed by 5-alkyl-4a-hydroxyisoalloxazines.
- Oonishi, Takahiro,Kawahara, Takayuki,Arakawa, Yukihiro,Minagawa, Keiji,Imada, Yasushi
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supporting information
p. 1791 - 1795
(2019/02/07)
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- Enzyme-like regiodivergent behavior of a flavopeptide catalyst in aerobic baeyer-villiger oxidation
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We recently developed a flavopeptide immobilized on polystyrene resin, Fl-Pep-PS, that could realize the first N5-unmodified neutral flavin (Fl)-catalyzed aerobic oxygenation reactions under non-enzymatic conditions. Although a key active species is assumed to be the corresponding 4a-hydroperoxyflavin (Fl4aOOH) from the unprecedented activity and unique chemoselectivity, further circumstantial support would be helpful to be sure since spectroscopic evidence is difficult to obtain due to the compound's insolubility. In this article, we report that the aerobic Baeyer-Villiger oxidation of a fused cyclobutanone, (±)-cis-bicyclo[3.2.0]hept-2-en-6-one (1), can be promoted with Fl-Pep-PS in a FMO-like chemoselectivity and regiodivergent manner via Fl-related catalytic intermediates, which delivers strong evidence of the involvement of Fl4aOOH as an active species in Fl-Pep-PScatalyzed aerobic oxygenation reactions.
- Yamanomoto, Ken,Kita, Hazuki,Arakawa, Yukihiro,Minagawaa, Keiji,Imada, Yasushi
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p. 866 - 869
(2019/01/21)
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- Biotransformation of dehydro-epi-androsterone by Aspergillus parasiticus: Metabolic evidences of BVMO activity
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The research on the synthesis of steroids and its derivatives is of high interest due to their clinical applications. A particular focus is given to molecules bearing a D-ring lactone like testolactone because of its bioactivity. The Aspergillus genus has been used to perform steroid biotransformations since it offers a toolbox of redox enzymes. In this work, the use of growing cells of Aspergillus parasiticus to study the bioconversion of dehydro-epi-androsterone (DHEA) is described, emphasizing the metabolic steps leading to D-ring lactonization products. It was observed that A. parasiticus is not only capable of transforming bicyclo[3.2.0]hept-2-en-6-one, the standard Baeyer-Villiger monooxygenase (BVMO) substrate, but also yielded testololactone and the homo-lactone 3β-hydroxy-17a-oxa-d-homoandrost-5-en-17-one from DHEA. Moreover, the biocatalyst degraded the lateral chain of cortisone by an oxidative route suggesting the action of a BVMO, thus providing enough metabolic evidences denoting the presence of BVMO activity in A. parasiticus. Furthermore, since excellent biotransformation rates were observed, A. parasiticus is a promising candidate for the production of bioactive lactone-based compounds of steroidal origin in larger scales.
- Mascotti, M. Laura,Palazzolo, Martín A.,Bisogno, Fabricio R.,Kurina-Sanz, Marcela
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- Baeyer-villiger oxidation and oxidative cascade reactions with aqueous hydrogen peroxide catalyzed by lipophilic Li[B(C6F5) 4] and Ca[B(C6F5)4]2
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Efficient and selective: Two lipophilic catalysts were used for Baeyer-Villiger (BV) oxidations to give lactones in high yields (see scheme). Cascade reactions involving this BV oxidation were used to selectively obtain either unsaturated carboxylic acids or hydroxylactones in high yields from β-silyl cyclohexanones. Copyright
- Uyanik, Muhammet,Nakashima, Daisuke,Ishihara, Kazuaki
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supporting information
p. 9093 - 9096
(2012/11/07)
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- Intramolecular Cyclopentene Annulation. 3. Synthesis and Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Bicyclic Cyclopentene Lactones as Potential Perhydroazulene and/or Monoterpene Synthons
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The internal cyclopropanation of several diversely substituted dienic diazo esters is described.Thermolysis of the resulting vinylcyclopropanes yielded cyclopentene-annulated lactones in good yields.Depending on the choice of the dienyl unit, either guaiane or pseudoguaiane substitution patterns of the cyclopentene portion were obtained.Stereochemical assignments based on 13C NMR data are provided for all of these lactones.Subsequent transformations of the bicyclic lactones to differentially functionalized cyclopentenes are described.The potential of these synthons in the synthesis of perhydroazulene sesquiterpenes and several monoterpene cyclopentanoid natural products is addressed.
- Hudlicky, Tomas,Reddy, D. Bhaskar,Govindan, S. V.,Kulp, Thomas,Still, Bobbi,Sheth, Jagdish P.
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p. 3422 - 3428
(2007/10/02)
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- Synthesis of (+/-)-Desmarestene and (+/-)-Viridiene, the Two Sperm Releasing and Attracting Pheromones from the Brown Algae Desmarestia aculeata and Desmarestia viridis
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Desmarestene 1 6-(1Z,3-butadienyl)-1,4-cycloheptadiene) and viridiene 3 cis-3-(1Z,3-butadienyl)-4-vinylcyclopentene) are chemical messengers for male gametes of the brown algae Desmarestia aculeata and Desmarestia viridis.Total syntheses of 1, 3 and their stereoisomers 1a, 3a-c are reported.Gas-chromatographic comparison of synthetic 1 and 3 with the corresponding natural products has established their structural identity.
- Boland, Wilhelm,Jakoby, Karin,Jaenicke, Lothar
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p. 2355 - 2362
(2007/10/02)
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