Total Synthesis of Neohedycaryol. Its Possible Role in the Biosynthesis of Eudesmane Sesquiterpenes

Minnaard, Adriaan J.; Stork, G. A.; Wijnberg, J. B. P. A.; Groot, Aede de

doi:10.1021/jo962056a

Cited by 18 publications

(8 citation statements)

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“…Direct deprotonation of this yields the observed 2- epi -α-eudesmol and β-eudesmol, while the diols are produced by prior addition of water, either following a 1,2-hydride shift (from C2 to C3) to produce eudesmane-2,11-diol, or immediately to produce the epimeric 2,3- epi -cryptomeridiol and 3- epi -cryptomeridiol. Critically, while acid hydrolysis of hedycarol has been reported to form eudesmols such as 2- epi -α-eudesmol and α-eudesmol (Jones and Sutherland, 1968; Minnaard et al , 1997), and the related diol 3-epi-cryptomeridiol also has been proposed to be generated by hydrolysis of hedycarol (Cornwell et al , 2000), here the enzymatic products were directly extracted with hexanes, which were further not passed over silica gel, excluding the possibility that these were generated by acid hydrolysis of hedycarol or a cyclic ether (e.g., of a 2,11-epoxy to generate eudesmane-2,11-diol).…”

Section: Resultsmentioning

confidence: 99%

“…In addition, acidic treatment of purified hedycarol led to formation of three eudesmol isomers (Figure S4B), consistent with previous investigation (Jones and Sutherland, 1968). This was carried out as described before (Minnaard et al , 1997). Specifically, hedycarol was dissolved in CH 2 Cl 2 and stirred with adding small amount of TsOH•H 2 O.…”

Section: Methodsmentioning

confidence: 99%

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Direct production of dihydroxylated sesquiterpenoids by a maize terpene synthase

et al. 2018

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The astounding structural and biological diversities of the large class of terpenoid natural products are imparted by both their complex hydrocarbon backbones and further elaboration by the addition of multiple hydroxyl groups, which provide both solubility and specific binding properties. While the role of terpene synthases (TPSs) in generating hydrocarbons with complex backbones is well known, these also are known to generate (singly) hydroxylated products by the addition of water prior to terminating deprotonation. Here a maize sesquiterpene synthase was unexpectedly found to generate dually hydroxylated products directly from (E,E)-farnesyl diphosphate, primarily eudesmane-2,11-diol, along with two closely related structural isomers. The unprecedented formation of these diols was proposed to proceed via initial addition of water to a germacradienyl intermediate, followed by protonation of the internal carbon-6,7-double-bond in the resulting hedycarol, with subsequent cyclization and further addition of water to an eudesmolyl intermediate. Evidence for the proposed mechanism was provided by labeling studies, as well as site-directed mutagenesis, based on structural modeling, which identified an active site phenylalanine required for the protonation and further elaboration of hedycaryol. This dihydroxylated sesquiterpenoid synthase was specifically expressed in maize roots and induced by pathogen infection, with its major enzymatic product only detected in root exudates or infected roots, suggesting a role in defense. Regardless of the ultimate metabolic fate or physiological role of these diols, this report not only reveals an unanticipated extension of the catalytic prowess of TPSs, but also provides insight into the underlying enzymatic mechanism.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Direct production of dihydroxylated sesquiterpenoids by a maize terpene synthase

et al. 2018

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“…formosana is remarkable, with the major constituents being biosynthetically related. Elemol, the major compound of the Type I oil, was issued from (2E,6E)-farnesyl diphosphate via the cyclodecadienyl structure of the germacrane skeleton [25] [26], whereas the bisabolyl cation, which leads to thujopsene, the major constituent of the Type II essential oil, is generally thought to be derived from nerolidyl diphosphate (Scheme).…”

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Phylogenetic Relationships of the Genus Chamaecyparis Inferred from Leaf Essential Oil

Chen

Lin

Cheng

et al. 2011

Chemistry & Biodiversity

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The species differentiation between Chamaecyparis formosensis, C. obtusa var. formosana, and C. obtusa, based on the composition of the leaf essential oils, was studied. The characterization of the oils by GC-FID and GC/MS analyses showed remarkable differences between these three essential oils. Cluster analysis (CA) and principal-component analysis (PCA) distinguished three groups of essential oils. The C. formosensis oil was dominated by α-pinene while those isolated from C. obtusa var. formosana and C. obtusa were characterized by high levels of (-)-thujopsene and α-terpinyl acetate, respectively. Moreover, the phylogenetic relationships of the genus Chamaecyparis were in agreement with previous findings based on morphological and molecular evidence. In addition, the essential oils from C. obtusa var. formosana could be classified into three chemical types, according to their different characteristic main compounds (β-elemol, (-)-thujopsene, and cis-thujopsenal). The biochemical correlations between the major constituents of the Chamaecyparis species were examined and their relationship is discussed.

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“…39 Por outro lado, a redução com L-selectride ® dos mesmos compostos produziu misturas dos álcoois alílicos epiméricos 6-10 em diferentes proporções (entradas 6-10). Esperava-se que os fatores estérico e estereoeletrônico competissem durante a aproximação do hidreto ao grupo carbonila, na presença de substituintes volumosos em posições remotas, como a isopropenila em C-7, agindo em conjunto com o grupo metila axial na cabeça-de-ponte.…”

Section: Resultsunclassified

Diastereosseletividade na redução de enonas bicíclicas com hidretos volumosos

Camozzato¹,

Tenius²,

Oliveira³

et al. 2008

Quím. Nova

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INTRODUÇÃOEste artigo é dedicado à memória da Profª. Helena Maria Carvalho Ferraz, que foi inspiradora da linha de pesquisa de síntese de sesquiterpenos em nosso laboratório, com o desenvolvimento da sín-tese da corimbolona, iniciada na década de 80.1 A partir dos anos 90, temos apresentado uma série de resultados de síntese, 2-6 de análise espectroscópica 7 e de estudos mecanísticos 8,9 envolvendo a química de sesquiterpenos, e todos eles, de certa maneira, foram influenciados pelos trabalhos da Profª. Ferraz. Em nosso trabalho na síntese de sesquiterpenos eudesmanos oticamente ativos e seus derivados, relatamos anteriormente uma eficiente preparação estereosseletiva das octalonas 1 e 4.2 Nosso método de preparação do composto 4 mostra-se até hoje como o mais eficiente relatado na literatura e tem sido utilizado para a obtenção de blocos de construção úteis na sín-tese de muitos e variados produtos naturais, por nós 3 e por outros. 10Na seqüência de nossos trabalhos sintéticos, temos a necessidade da preparação diastereocontrolada do álcool alílico pseudoaxial 9b. Este composto pode ser obtido pela redução da 14-nor-α-ciperona (4) em 2 etapas, com inversão de configuração do álcool. Temos contudo a necessidade de um método de redução direta de 4 para 9b. Nos últimos 30 anos, têm sido muito estudados e relatados na literatura métodos de redução estereocontrolada de cetonas cíclicas e cetonas cíclicas α,β-insaturadas. Hidretos pouco volumosos como NaBH 4 , LiAlH 4 e derivados foram avaliados exaustivamente, 11-16 bem como metais alcalinos em solução. 17 Resultados experimentais envolvendo cicloexanonas e cicloexenonas substituídas como substratos demonstraram que a direção preferencial do ataque ao anel (axial ou equatorial) possui forte dependência tanto do volume do hidreto atacante quanto do volume dos substituintes ao redor da carbonila. Hidretos pouco volumosos, como NaBH 4 e LiAlH 4 , preferem quase exclusivamente ataques axiais, gerando álcoois pseudoequatoriais com diastereosseletividades variando de 72 a >96%. [12][13][14][15][16] Os modelos estereoquímicos mais aceitos para explicar esta preferência por um ataque axial são baseados em conceitos como o controle pela estabilidade do produto, e em uma abordagem estérica, pelos efeitos dos hidrogênios α-carbonila axiais, que podem repelir e/ou desenvolver efeito torsional quando de ataques equatoriais, e pelos efeitos estéricos dos hidrogênios β-carbonila axiais (Figura 1). Estudos computacionais 18-25 confirmaram que tanto efeitos eletrônicos quanto torsionais estão estreitamente relacionados à seleção facial na redução do sistema cicloexanona. A melhor orientação antiperiplanar do nucleófilo com a ligação C-H adjacente em um ataque axial leva a uma deslocalização hiperconjugativa da ligação Cα-H ax para um ataque axial e da ligação Cα-Cβ para um ataque equatorial.

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Total Synthesis of Neohedycaryol. Its Possible Role in the Biosynthesis of Eudesmane Sesquiterpenes

Cited by 18 publications

References 48 publications

Direct production of dihydroxylated sesquiterpenoids by a maize terpene synthase

Direct production of dihydroxylated sesquiterpenoids by a maize terpene synthase

Phylogenetic Relationships of the Genus Chamaecyparis Inferred from Leaf Essential Oil

Diastereosseletividade na redução de enonas bicíclicas com hidretos volumosos

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