scholarly journals Stereospecific Epoxidation of Limonene Catalyzed by Peroxygenase from Oat Seeds

Antioxidants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1462
Author(s):  
Daniela Maria Biondi ◽  
Claudia Sanfilippo ◽  
Angela Patti
Keyword(s):  
Avena Sativa ◽  
Ring Opening ◽  
Main Product ◽  
Toxic Metal ◽  
Value Added ◽  
Epoxide Ring ◽  
Proof Of Concept ◽  
Naturally Occurring ◽  
Oat Seeds ◽  
Operational Simplicity

Limonene is one of the most abundant naturally occurring cyclic monoterpenes and has recently emerged as a sustainable alternative to petroleum-based solvents as well as a chemical platform for the production of value-added compounds. The biocatalytic epoxidation of both enantiomers of limonene was carried out in the presence of a peroxygenase-containing preparation from oat (Avena sativa) flour. Different reaction profiles were observed depending on the starting enantiomer of limonene, but in both cases the 1,2-monoepoxide was obtained as the main product with excellent diastereoselectivity. Trans-1,2-monoepoxide and cis-1,2-monoepoxide were isolated from the reaction of (R)-limonene and (S)-limonene, respectively, and the reactions were scaled-up to 0.17 M substrate concentration. The process is valuable for operational simplicity, lack of toxic metal catalysts, and cost-effectiveness of the enzymatic source. Pure stereoisomers of 1,2-monoepoxides of limonene constitute a useful starting material for biorenewable polymers, but can be also converted into other chiral derivatives by epoxide ring opening with nucleophiles. As a proof of concept, a tandem protocol for the preparation of enantiopure (1S,2S,4R)-1,2-diol from (R)-limonene and (1R,2R,4S)-1,2-diol from (S)-limonene was developed.

Asymmetric total synthesis of cryptoconcatone I

2019 ◽  
Vol 17 (14) ◽  
pp. 3552-3566 ◽  
Author(s):  
Ranjan Kumar Acharyya ◽  
Pratik Pal ◽  
Shrestha Chatterjee ◽  
Samik Nanda
Keyword(s):  
Total Synthesis ◽  
Late Stage ◽  
Ring Opening ◽  
Epoxide Ring ◽  
Asymmetric Total Synthesis ◽  
Epoxide Ring Opening ◽  
Cascade Cyclization ◽  
Naturally Occurring

An efficient asymmetric total synthesis of naturally occurring γ-Z-butenolide cryptoconcatone I was achieved by employing substrate-directed reductive epoxide ring opening and late-stage “Pd–Cu” catalyzed cascade cyclization.

Preparation of New Polyols Based on Cis-1,4-Polyisoprene by Using 1,3-Dipolar Cycloaddition

2013 ◽  
Vol 844 ◽  
pp. 381-384
Author(s):  
Ekasit Anancharoenwong ◽  
Jean Francois Pilard ◽  
Irène Campistron ◽  
Albert Laguerre ◽  
Frédéric Gohier ◽  
...  
Keyword(s):  
Ring Opening ◽  
Click Reaction ◽  
Value Added ◽  
Polyol Synthesis ◽  
Sodium Ascorbate ◽  
Dipolar Cycloaddition ◽  
Epoxide Ring ◽  
Terminal Alkyne ◽  
Epoxide Ring Opening ◽  
Model Molecule

This research focuses on synthesis and modification of polyol precursors derived from cis-1,4-polyisoprene (PI). These new polyol precursors can be converted to high value-added polyurethane (PU). The epoxidized hydroxytelechelic PI (EHTPI) prepared by chemical modification from PI was used as starting material for polyol synthesis. 1,3-Dipolar cycloaddition between a terminal alkyne and an azide has rapidly become the most popular click reaction. We applied this reaction to couple azide-functionalized PI and alkyne-functionalized sugar for preparing polyols. For azide functionalization, 1-methyl epoxidized cyclohexane was used as a model molecule, and various conditions for epoxide ring opening of 1-methyl epoxidized cyclohexane and EHTPI were investigated. The cycloaddition of alkyne and azide was carried out in the presence of sodium ascorbate and copper sulfate. The polyol precursors obtained might be used to prepare biodegradable polyol PU.

Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols

2019 ◽  
Author(s):  
Ke-Yin Ye ◽  
Terry McCallum ◽  
Song Lin
Keyword(s):  
Ring Opening ◽  
High Reactivity ◽  
Hydrogen Atom Transfer ◽  
Organic Radicals ◽  
Epoxide Ring ◽  
Allylic Alcohols ◽  
Epoxide Ring Opening ◽  
Bond Forming ◽  
Co Catalysts ◽  
The Rich

Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton-transfer/electron-transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.<br>

Construction the A-B bicyclic ring structure of Stemocurtisisne

2020 ◽  
Vol 17 ◽  
Author(s):  
Duc Dau Xuan
Keyword(s):  
Glutamic Acid ◽  
Natural Product ◽  
Mannich Reaction ◽  
Boronic Acid ◽  
Ring Opening ◽  
Ring Structure ◽  
Starting Material ◽  
Epoxide Ring ◽  
Epoxide Ring Opening

: The synthesis of the A-B bicyclic ring structure 3 of the natural product Stemocurtisine is described. The synthesis was accomplished in seven synthetic steps from commercially available L-glutamic acid. The key step involved a borono-Mannich reaction between the hemiaminal 6 and trans-β-styryl boronic acid and trans-β-styrylpotassiumtrifluoroborate to prepare the cis diene 4. Attempts to prepare the A-B-C ring compound 2 via intramolecular epoxide ring opening followed by rearangement under different basic conditions were unsuccessful. Only unreactive starting material was recovered.

scholarly journals Thermal and Electrochemical Properties of Solid Polymer Electrolytes Prepared via Lithium Salt-Catalyzed Epoxide Ring Opening Polymerization

2021 ◽  
Vol 11 (4) ◽  
pp. 1561
Author(s):  
Gabrielle Foran ◽  
Nina Verdier ◽  
David Lepage ◽  
Arnaud Prébé ◽  
David Aymé-Perrot ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Polymer Electrolytes ◽  
Ring Opening ◽  
Lithium Salt ◽  
Ring Opening Polymerization ◽  
Solid Polymer Electrolytes ◽  
Solid Polymer ◽  
Polymerization Reaction ◽  
Epoxide Ring ◽  
Epoxide Ring Opening

Solid polymer electrolytes have been widely proposed for use in all solid-state lithium batteries. Advantages of polymer electrolytes over liquid and ceramic electrolytes include their flexibility, tunability and easy processability. An additional benefit of using some types of polymers for electrolytes is that they can be processed without the use of solvents. An example of polymers that are compatible with solvent-free processing is epoxide-containing precursors that can form films via the lithium salt-catalyzed epoxide ring opening polymerization reaction. Many polymers with epoxide functional groups are liquid under ambient conditions and can be used to directly dissolve lithium salts, allowing the reaction to be performed in a single reaction vessel under mild conditions. The existence of a variety of epoxide-containing polymers opens the possibility for significant customization of the resultant films. This review discusses several varieties of epoxide-based polymer electrolytes (polyethylene, silicone-based, amine and plasticizer-containing) and to compare them based on their thermal and electrochemical properties.

scholarly journals Comparative Time-Course Physiological Responses and Proteomic Analysis of Melatonin Priming on Promoting Germination in Aged Oat (Avena sativa L.) Seeds

2021 ◽  
Vol 22 (2) ◽  
pp. 811
Author(s):  
Huifang Yan ◽  
Peisheng Mao
Keyword(s):  
Antioxidant Capacity ◽  
Avena Sativa ◽  
Proteomic Analysis ◽  
Time Course ◽  
Intact Cell ◽  
Membrane Integrity ◽  
Acid Synthesis ◽  
Ultrastructural Changes ◽  
Oat Seeds ◽  
Aged Seeds

Melatonin priming is an effective strategy to improve the germination of aged oat (Avena sativa L.) seeds, but the mechanism involved in its time-course responses has remained largely unknown. In the present study, the phenotypic differences, ultrastructural changes, physiological characteristics, and proteomic profiles were examined in aged and melatonin-primed seed (with 10 μM melatonin treatment for 12, 24, and 36 h). Thus, 36 h priming (T36) had a better remediation effect on aged seeds, reflecting in the improved germinability and seedlings, relatively intact cell ultrastructures, and enhanced antioxidant capacity. Proteomic analysis revealed 201 differentially abundant proteins between aged and T36 seeds, of which 96 were up-accumulated. In melatonin-primed seeds, the restoration of membrane integrity by improved antioxidant capacity, which was affected by the stimulation of jasmonic acid synthesis via up-accumulation of 12-oxo-phytodienoic acid reductase, might be a candidate mechanism. Moreover, the relatively intact ultrastructures enabled amino acid metabolism and phenylpropanoid biosynthesis, which were closely associated with energy generation through intermediates of pyruvate, phosphoenolpyruvate, fumarate, and α-ketoglutarate, thus providing energy, active amino acids, and secondary metabolites necessary for germination improvement of aged seeds. These findings clarify the time-course related pathways associated with melatonin priming on promoting the germination of aged oat seeds.

ChemInform Abstract: NEIGHBORING GROUP EFFECTS IN EPOXIDE RING OPENING, CIS-EPOXY-ALCOHOLS

1976 ◽  
Vol 7 (42) ◽  
pp. no-no
Author(s):  
ERWIN GLOTTER ◽  
PNINA KRINSKY ◽  
MIRIAM REJTOE ◽  
MARTIN WEISSENBERG
Keyword(s):  
Ring Opening ◽  
Epoxide Ring ◽  
Neighboring Group ◽  
Epoxide Ring Opening ◽  
Epoxy Alcohols ◽  
Group Effects

An analysis of the factors contributing to the regioselectivity observed in the opening of oxiranes

1980 ◽  
Vol 58 (3) ◽  
pp. 302-306 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Oxygen Atom ◽  
Ring Opening ◽  
Oxirane Ring ◽  
Epoxide Ring ◽  
Acid Base ◽  
Epoxide Ring Opening ◽  
Soft Acid ◽  
Hsab Theory

The regioselectivity of epoxide ring opening can be analyzed in terms of hard–soft acid–base (HSAB) theory. The coordination of the hard acid with the oxygen atom of the oxirane ring produces a "pulling effect" which determines the direction of the ring opening. In the absence of a strong "pulling effect" the "pushing effect" of the approaching base is examined and the consequences of relative softness or hardness of the nucleophile on the regioselectivity of the ring opening are discussed.

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