Oxidations of valencene

Shaffer, Gary W.; Eschinasi, Emile H.; Purzycki, Kenneth L.; Doerr, Anne B.

doi:10.1021/jo00903a010

Cited by 30 publications

(17 citation statements)

References 8 publications

(18 reference statements)

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“…The relative mobilities (R f values) for monohydroxylated sesquiterpenes are as follows: solavetivol, nootkatol, epiaristolochen-2␤-ol, and 4-epieremophilen-2␤-ol were 0.27, 0.26, 0.25, and 0.32, respectively. Additional purification of the alcohols was accomplished by C 18 Reference standards of nootkatol (␤-nootkatol) and 2-epinootkatol (␣-nootkatol) were prepared by LiAlH 4 reduction of nootkatone in ether according to literature procedures (25,26). Purification by flash chromatography on silica gel (5:1, hexane/ ethyl acetate) provided pure samples of the nootkatol isomers in a 96.5:3.5 ratio (68% combined yield).…”

Section: Gc and Gc-ms Analyses Of Cyp Reactions-quantificationmentioning

confidence: 99%

Functional Characterization of Premnaspirodiene Oxygenase, a Cytochrome P450 Catalyzing Regio- and Stereo-specific Hydroxylations of Diverse Sesquiterpene Substrates

Takahashi

Yeo

Zhao

et al. 2007

Journal of Biological Chemistry

107

105

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Solavetivone, a potent antifungal phytoalexin, is derived from a vetispirane-type sesquiterpene, premnaspirodiene, by a putative regio-and stereo-specific hydroxylation, followed by a second oxidation to yield the ␣,␤-unsaturated ketone. Mechanistically, these reactions could occur via a single, multifunctional cytochrome P450 or some combination of cytochrome P450s and a dehydrogenase. We report here the characterization of a single cytochrome P450 enzyme, Hyoscyamus muticus premnaspirodiene oxygenase (HPO), that catalyzes these successive reactions at carbon 2 (C-2) of the spirane substrate. HPO also catalyzes the equivalent regio-specific (C-2) hydroxylation of several eremophilane-type (decalin ring system) sesquiterpenes, such as with 5-epi-aristolochene. Moreover, HPO displays interesting comparisons to other sesquiterpene hydroxylases. 5-Epi-aristolochene di-hydroxylase (EAH) differs catalytically from HPO by introducing hydroxyl groups first at C-1, then C-3 of 5-epi-aristolochene. HPO and EAH also differ from one another by 91-amino acid differences, with four of these differences mapping to putative substrate recognition regions 5 and 6. These four positions were mutagenized alone and in various combinations in both HPO and EAH and the mutant enzymes were characterized for changes in substrate selectivity, reaction product specificity, and kinetic properties. These mutations did not alter the regio-or stereo-specificity of either HPO or EAH, but specific combinations of the mutations did improve the catalytic efficiencies 10 -15-fold. Molecular models and comparisons between HPO and EAH provide insights into the catalytic properties of these enzymes of specialized metabolism in plants.

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Section: Gc and Gc-ms Analyses Of Cyp Reactions-quantificationmentioning

confidence: 99%

Functional Characterization of Premnaspirodiene Oxygenase, a Cytochrome P450 Catalyzing Regio- and Stereo-specific Hydroxylations of Diverse Sesquiterpene Substrates

Takahashi

Yeo

Zhao

et al. 2007

Journal of Biological Chemistry

107

105

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“…Singlet oxygen, 1 O2 ( 1 Δg), readily reacts with the trisubstituted double bond of (+)-valencene, according to the ene reaction providing selectively two regioisomers. The photooxidation of (+)-valencene into hydroperoxides by photochemically generated 1 O2 has already been reported [22,38,39]. The reactions were typically carried out in a methanol/benzene (1:1) mixture in the presence of rose Bengal.…”

Section: Resultsmentioning

confidence: 99%

“…The oxidation of (+)-valencene with the carcinogenic tert-butyl chromate or sodium dichromate was reported by Hunter et al [21] and Shaffer et al [22]. Tert-butyl peracetate was also used for allylic oxidation of valencene, but additional chromic acid was required for the oxidation of intermediate nootkatol [23].…”

Section: Introductionmentioning

confidence: 95%

One-Pot Synthesis of (+)-Nootkatone via Dark Singlet Oxygenation of Valencene: The Triple Role of the Amphiphilic Molybdate Catalyst

et al. 2016

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Efficient one-pot catalytic synthesis of (+)-nootkatone was performed from (+)-valencene using only hydrogen peroxide and amphiphilic molybdate ions. The process required no solvent and proceeded in three cascade reactions: (i) singlet oxygenation of valencene according to the ene reaction; (ii) Schenck rearrangement of one hydroperoxide into the secondary β-hydroperoxide; and (iii) dehydration of the hydroperoxide into the desired (+)-nootkatone. The solvent effect on the hydroperoxide rearrangement is herein discussed. The amphiphilic dimethyldioctyl ammonium molybdate, which is also a balanced surfactant, played a triple role in this process, as molybdate ions catalyzed at both Step 1 and Step 3 and it allowed the rapid formation of a three-phase microemulsion system that highly facilitates product recovery. Preparative synthesis of the high added value (+)-nootkatone was thus performed at room temperature with an isolated yield of 46.5%. This is also the first example of a conversion of allylic hydroperoxides into ketones catalyzed by molybdate ions.

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“…By reviewing the above references, one can conclude that there is some confusion in the literature about the absolute configuration of the alcohol moiety at C-2 of the natural product, which was sometimes called nootkatol [ 5 , 8 ] and sometimes epinootkatol [ 7 , 9 , 10 ]. To clarify this point in the literature, a clear-cut method with the ability to unambiguously determine the absolute configuration of C-2 on nootkatol needs to be implemented.…”

Section: Resultsmentioning

confidence: 99%

Biologically Important Eremophilane Sesquiterpenes from Alaska Cedar Heartwood Essential Oil and Their Semi-Synthetic Derivatives

et al. 2011

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The essential oil of Alaska cedar heartwood is known to contain compounds which contribute to the remarkable durability of this species. While previous research has identified several compounds, a complete description of this oil has not been undertaken. In this research a profile of the oil is given in which the major components are identified by GC, isolation and spectroscopic techniques. The major components of the steam distilled essential oil were identified as nootkatin, nootkatone, valencene, nootaktene, carvacrol, methyl carvacrol, nootkatol (2), and eremophil-1(10),11-dien-13-ol (3). The last two compounds were isolated for the first time from Alaska cedar in this research. The absolute stereochemistry at C-2 of nootkatol was shown to have the (S) configuration using the Mosher ester method. Assignment of stereochemistry for valencene-13-ol (3) was established by synthesis from valencene (6). Finally, two related sesquiterpenoids were synthesized from nootkatone and valencene. These sesquiterpenoids were nootkatone-1,10-11,12-diepoxide (5) and valencene-13-aldehyde (4), respectively.

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Oxidations of valencene

Cited by 30 publications

References 8 publications

Functional Characterization of Premnaspirodiene Oxygenase, a Cytochrome P450 Catalyzing Regio- and Stereo-specific Hydroxylations of Diverse Sesquiterpene Substrates

Functional Characterization of Premnaspirodiene Oxygenase, a Cytochrome P450 Catalyzing Regio- and Stereo-specific Hydroxylations of Diverse Sesquiterpene Substrates

One-Pot Synthesis of (+)-Nootkatone via Dark Singlet Oxygenation of Valencene: The Triple Role of the Amphiphilic Molybdate Catalyst

Biologically Important Eremophilane Sesquiterpenes from Alaska Cedar Heartwood Essential Oil and Their Semi-Synthetic Derivatives

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