18383-51-2Relevant articles and documents
A candidate cDNA clone for (-)-limonene-7-hydroxylase from Perilla frutescens
Mau, Christopher J.D.,Karp, Frank,Ito, Michiho,Honda, Gisho,Croteau, Rodney B.
, p. 373 - 379 (2010)
Cytochrome P450 mono-oxygenases from peppermint, spearmint and perilla (all members of the family Lamiaceae) mediate the regiospecific hydroxylation of the parent olefin (-)-limonene to produce essential oil components oxygenated at C3, C6 and C7, respectively. Cloning, expression and mutagenesis of cDNAs encoding the peppermint limonene-3-hydroxylase and the spearmint limonene-6-hydroxylase have allowed the identification of a single amino acid residue which determines the regiospecificity of oxygenation by these two enzymes. A hybridization strategy provided a cytochrome P450 limonene hydroxylase cDNA from perilla with which to further evaluate the structural determinants of regiospecificity for oxygenation of the common substrate (-)-limonene. The perilla cDNA was a partial clone of 1550 bp (lacking the N-terminal membrane insertion domain), and shared 66% identity with the peppermint 3-hydroxylase and spearmint 6-hydroxylase at the amino acid level. The perilla cytochrome P450 was expressed in Escherichia coli as a chimeric protein fused with the N-terminal membrane insertion domain of the limonene-3-hydroxylase. The kinetically competent recombinant protein was characterized and shown to produce a mixture of C3-, C6- and C7-hydroxylated limonene derivatives with a distribution of 33%, 14% and 53%, respectively.
A study of some molecularly imprinted polymers as protic catalysts for the isomerisation of α-pinene oxide to trans-carveol
Motherwell, William B.,Bingham, Matilda J.,Pothier, Julien,Six, Yvan
, p. 3231 - 3241 (2004)
A range of acidic Molecularly Imprinted Polymers (MIPs) were synthesised using the imprint molecule trans-carvyl amine as a transition state analogue for the selective isomerisation of α-pinene oxide to trans-carveol. The amine functionality of the imprint molecule was used to selectively position a sulfonic acid group in the MIP binding pocket utilising 4-styrene sulfonic acid as the functional monomer. Co-polymerisation with varying ratios of styrene and divinylbenzene afforded a range of MIPs which were tested for their ability to effect selective formation of trans-carveol from α-pinene oxide. Although successful imprinting was demonstrated in binding studies, it was shown that solvent effects were dominant in effecting selective formation of trans-carveol. Using DMF as solvent, up to 70% of the products from acid catalysed isomerisation of α-pinene oxide with the polystyrene MIPs were obtained via the necessary para menthyl tertiary carbocation, and industrially important trans-carveol was obtained in 45% yield.
Phosphotungstic acid as a versatile catalyst for the synthesis of fragrance compounds by α-pinene oxide isomerization: Solvent-induced chemoselectivity
Da Silva Rocha, Kelly A.,Hoehne, Juliana L.,Gusevskaya, Elena V.
, p. 6166 - 6172 (2008)
The remarkable effect of the solvent on the catalytic performance of H 3PW12O40, the strongest heteropoly acid in the Keggin series, allows direction of the transformations of α-pinene oxide (1) to either campholenic aldehyde (2), trans-carveol (3), trans-sobrerol (4a), or pinol (5). Each of these expensive fragrance compounds was obtained in good to excellent yields by using an appropriate solvent. Solvent polarity and basicity strongly affect the reaction pathways: nonpolar nonbasic solvents favor the formation of aldehyde 2; polar basic solvents favor the formation of alcohol 3; whereas in polar weakly basic solvents, the major products are compounds 4a and 5. On the other hand, in 1,4-dioxane, which is a nonpolar basic solvent, both aldehyde 2 and alcohol 3 are formed in comparable amounts. The use of very low catalyst loading (0.005-1 mol%) and the possibility of catalyst recovery and recycling without neutralization are significant advantages of this simple, environmentally benign, and low-cost method. This method represents the first example of the synthesis of isomers from α-pinene oxide, other than campholenic aldehyde, with a selectivity that is sufficient for practical usage.
Pauson-Khand Reactions with Concomitant C?O Bond Cleavage for the Preparation of 5,5- 5,6- and 5,7-Bicyclic Ring Systems
Ma, Ding,Hu, Naifeng,Ao, Junli,Zang, Shaoli,Yu, Guo,Liang, Guangxin
supporting information, p. 1887 - 1891 (2021/02/26)
Pauson-Khand reactions (PKR) with concomitant C?O bond cleavage have been developed for construction of 5,5- 5,6- and 5,7-bicyclic ring systems bearing complex stereochemistry. The chemistry generates intermolecular PKR-type products in an absolute regio- and stereochemical control which is hardly achievable through real intermolecular Pauson-Khand reactions. A mechanism for this Pauson-Khand reaction has been proposed based on deuterium labelling experiments. (Figure presented.).
Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
supporting information, p. 21176 - 21182 (2020/09/17)
Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
