- Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus - Conversion of selected spirocyclic terpenoids and computational analysis
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Allylic oxidations of olefins to enones allow the efficient synthesis of value-added products from simple olefinic precursors like terpenes or terpenoids. Biocatalytic variants have a large potential for industrial applications, particularly in the pharmaceutical and food industry. Herein we report efficient biocatalytic allylic oxidations of spirocyclic terpenoids by a lyophilisate of the edible fungus Pleurotus sapidus. This ''mushroom catalysis'' is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio- and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been developed. The oxidations follow a radical mechanism and the regioselectivity of the reaction is mainly determined by bond-dissociation energies of the available allylic CH-bonds and steric accessibility of the oxidation site.
- Weidmann, Verena,Schaffrath, Mathias,Zorn, Holger,Rehbein, Julia,Maison, Wolfgang
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supporting information
p. 2233 - 2241
(2014/01/06)
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- Syntheses of theaspirone and vitispirane via palladium(II)-catalyzed oxaspirocyclization
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Total syntheses of theaspirone (A and B) and vitispirane (A and B) are described. The key step in the syntheses is the palladium(II)-catalyzed intramolecular oxaspirocyclization of diene alcohol 4 to either vitispirane or the allylic alcohol 9. The outcome of the oxaspirocyclization is very much dependent on the solvent employed. In water-acetic acid (4:1) a 1:1 mixture of the diastereomeric alcohols 9A and 9B was exclusively formed. In water with 8 equiv of a strong non-nucleophilic acid, vitispiranes A and B (1:1) were obtained. An alternative procedure to obtain vitispirane with the use of LiCl and K2CO3 is described. In the latter reaction vitispirane B is formed preferentially. This result is explained by an equilibrium between the two possible π-allyl complexes 5A and 5B, the kinetically favored 5B being transformed into vitispirane 3B before isomerization to 5A occurs.
- Nilsson, Ylva I. M.,Aranyos, Attila,Andersson, Pher G.,Baeckvall, Jan-E.,Parrain, Jean-Luc,Ploteau, Christelle,Quintard, Jean-Paul
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p. 1825 - 1829
(2007/10/03)
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- A New Route to Vitispiranes
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Diastereoisomeric vitispiranes have been synthesized from 2,6,6-trimethyl-1-(3-oxo-1-butenyl)-1,3-cyclohexadiene by five-step reactions including photooxygenation.
- Kato, Tetsuya,Kondo, Hisao
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p. 1573 - 1574
(2007/10/02)
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- New Syntheses of Edulans and Theaspiranes from α-Inone
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New syntheses of edulans and theaspiranes are described.The key step involves the cyclization of 4-(2',6',6'-trimethyl-2'-hydroxy-3'-cyclohexen-1'-yl)-butan-2-ol (7) and 4-(2',6',6'-trimethyl-1',2'-dihydroxy-3'-cyclohexen-1'-yl)-butan-2-ol (8) derived from α-ionone.The diol (7) and triol (8) were cyclized with acetic acid into the corresponding tetrahydropyran derivatives ; the latter two compounds were dehydrated to edulan I and II (13a, 13b).On treatment with tosyl chloride in pyridine, however, triol (8) gave spiro-compounds (11a, 11b and 12); (11a and 11b) were easily converted to cis- and trans-theaspirone by oxidation and 5,6-erythro-6-hydroxy-dihydrotheaspiranes (15a and 15b) by reduction.
- Etoh, Hideo,Ina, Kazuo,Iguchi, Masanobu
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p. 2871 - 2876
(2007/10/02)
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