177698-19-0Relevant articles and documents
Converting S-limonene synthase to pinene or phellandrene synthases reveals the plasticity of the active site
Xu, Jinkun,Ai, Ying,Wang, Jianhui,Xu, Jingwei,Zhang, Yongkang,Yang, Dong
, p. 34 - 41 (2017/03/27)
S-limonene synthase is a model monoterpene synthase that cyclizes geranyl pyrophosphate (GPP) to form S-limonene. It is a relatively specific enzyme as the majority of its products are composed of limonene. In this study, we converted it to pinene or phellandrene synthases after introducing N345A/L423A/S454A or N345I mutations. Further studies on N345 suggest the polarity of this residue plays a critical role in limonene production by stabilizing the terpinyl cation intermediate. If it is mutated to a non-polar residue, further cyclization or hydride shifts occurs so the carbocation migrates towards the pyrophosphate, leading to the production of pinene or phellandrene. On the other hand, mutant enzymes that still possess a polar residue at this position produce limonene as the major product. N345 is not the only polar residue that may stabilize the terpinyl cation because it is not strictly conserved among limonene synthases across species and there are also several other polar residues in this area. These residues could form a “polar pocket” that may collectively play this stabilizing role. Our study provides important insights into the catalytic mechanism of limonene synthases. Furthermore, it also has wider implications on the evolution of terpene synthases.
Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
-
, (2015/03/03)
The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
Effect of high-temperature calcination on the generation of Bronsted acid sites on WO3/Al2O3
Kitano, Tomoyuki,Hayashi, Tomohiro,Uesaka, Toshio,Shishido, Tetsuya,Teramura, Kentaro,Tanaka, Tsunehiro
, p. 2011 - 2020 (2014/08/05)
The acid properties of a series of alumina-supported tungsten oxide (WO3/Al2O3) catalysts with loadings of 5-50 wt% WO3 calcined at various temperatures were investigated by acid-catalyzed reactions (benzylation of anisole and isomerization of α-pinene) and FTIR spectroscopy. The relationships between acid properties, structures, and catalytic performances were evaluated. Both the catalytic activity and amount of Bronsted acid sites depend on the calcination temperature and WO3 loading. High-temperature calcination (1123 K) generated Bronsted acid properties, and 20 wt% WO 3/Al2O3 calcined at 1123 K exhibited the highest activity among the catalysts tested. The activities for the benzylation of anisole and α-pinene isomerization over WO3/Al 2O3 calcined at 1123 K were proportional to the Bronsted acidity, which indicates that these reactions occurred on the Bronsted acid sites. Tungsten oxide, which has distorted octahedral symmetry, was loaded as 2D monolayer domains below 20 wt%, and these domains covered most of the alumina surface at 20 wt%. If the WO3 loading was sufficient to form 2D tungsten oxide monolayer sheets (>20 wt%), some of the Bronsted acid sites on WO3/Al2O3 were obscured by monoclinic WO3 that has no Bronsted acid sites, which resulted in a decrease of the catalytic activity. This suggests that Bronsted acid sites are generated at the boundaries between tungsten oxide monolayer domains.
Unique catalysis of gold nanoparticles in the chemoselective hydrogenolysis with H2: Cooperative effect between small gold nanoparticles and a basic support
Noujima, Akifumi,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
, p. 6723 - 6725 (2012/07/28)
Gold nanoparticles on hydrotalcite act as a heterogeneous catalyst for the chemoselective hydrogenolysis of various allylic carbonates to the corresponding terminal alkenes using H2 as a clean reductant. The combination of gold nanoparticles and basic supports elicited significantly unique and selective catalysis in the hydrogenolysis.
Catalytic activity of the VIII group metals in the hydrogenation and isomerization of α- And β-pinenes
Deliy,Simakova
body text, p. 2056 - 2064 (2010/05/02)
The kinetic regularities of the liquid-phase hydrogenation and isomerization of α- and β-pinenes over the Pd/C, Ru/C, Rh/C, Pt/C, and Ir/C catalysts were studied at temperatures ranging from 20 to 100 °C and at hydrogen pressures of 1-11 bar using n-octane as the solvent. The hydrogenation and isomerization of α- and β-pinenes occur simultaneously on the Ru/C, Rh/C, Pt/C, and Ir/C catalysts, and the reaction mixture contains the products of double bond hydrogenation, viz., cis- and trans-pinanes. The Ru, Rh, and Pd metals have a higher catalytic activity in β-pinene isomerization than Ir and Pt. Among the VIII Group metals studied, the Pd-based catalyst has the highest catalytic activity in double bond isomerization of α- and β-pinenes. The general scheme of the mechanism of hydrogenation and isomerization of α- and β-pinenes on the Pd/C catalyst was proposed.
Biochemistry and molecular genetics of the biosynthesis of the earthy odorant methylisoborneol in Streptomyces coelicolor
Wang, Chieh-Mei,Cane, David E.
supporting information; experimental part, p. 8908 - 8909 (2009/02/03)
Methylisoborneol (2) is a volatile organic compound produced by a wide variety of Actinomycete soil organisms, myxobacteria, and cyanobacteria. It has an unusually low odor threshold and, together with geosmin, is responsible for the characteristic smell of moist soil as well as unpleasant taste and odor episodes associated with public water supplies and contamination of various foodstuffs, including fish, wine, and beer. Despite considerable interest in detection and remediation of methylisoborneol, the biosynthesis of this methylated monoterpene has been obscure. In Streptomyces coelicolor, the sco7700 and sco7701 genes are shown to correspond to a two-gene operon responsible for methylisoborneol biosynthesis. Both genes have been amplified by PCR and the resulting DNA has been cloned and expressed in Escherichia coli. Incubation of recombinant SCO7701 protein, annotated as a possible C-methyltransferase, with geranyl diphosphate (1) and S-adenosylmethionine gave the previously unknown compound, (E)-2-methylgeranyl diphosphate (3). Incubation of 3 in the presence of Mg2+ with recombinant SCO7700, previously annotated only as a possible metal-binding protein or terpenoid synthase, resulted in the formation of 2-methylisoborneol (2). The steady-state kinetic parameters for both biochemical reactions have been determined. Incubation of geranyl diphosphate and S-adenosylmethionine with a mixture of both SCO7700 and SCO7701 resulted in formation of methylisoborneol (2). Cyclization of 2-methylgeranyl diphosphate (3) to methylisoborneol (2) likely involves the intermediacy of 2-methyllinalyl diphosphate. Copyright
Isomerization of α-pinene over dealuminated ferrierite-type zeolites
Rachwalik, Rafal,Olejniczak, Zbigniew,Jiao, Jian,Huang, Jun,Hunger, Michael,Sulikowski, Bogdan
, p. 161 - 170 (2008/09/17)
Isomerization of α-pinene was performed on a series of dealuminated ferrierite (FER)-type zeolites in liquid phase at 363 K using a batch reactor. The course of zeolite dealumination was followed in detail using 29Si, 27Al, 1H MAS NMR, XRD, FTIR, and sorption of nitrogen. The ammonium form of FER was dealuminated with aqueous solutions of HCl. While retaining the crystallinity of the zeolite particles, the treatments removed up to 53% of the tetrahedrally coordinated aluminum atoms from the FER framework. According to 29Si MAS NMR studies, the framework aluminum atoms located at the 10-membered rings in the main channels of FER (TB sites) were depleted preferentially from their positions. Even relatively mild dealumination of FER led to an active catalyst containing both Bronsted and Lewis centers, yielding up to 97% conversion of α-pinene at 363 K, in contrast to the 72% observed for the parent hydrogen form. Such catalytic behavior was discussed in terms of the conversion of a reactant inside micropores of the zeolite catalyst, on Bronsted acid centers with enhanced strength located probably in the vicinity of Lewis sites. The selectivity toward camphene and limonene changed smoothly with the dealumination level; thus, a higher selectivity toward limonene was observed at the expense of camphene formation with increasing the nSi / nAl ratio of the catalysts. The selectivity toward camphene and limonene was close to 85% for all of the materials studied. The initial rates of α-pinene transformations over FER-type materials exceeded those observed for other catalytic systems, heteropoly acid/SiO2 and H2SO4/ZrO2. This study demonstrates the successful application of a medium-pore zeolite for the catalytic transformation of α-pinene in liquid phase.
A cDNA clone for β-caryophyllene synthase from Artemisia annua
Cai, Yu,Jia, Jun-Wei,Crock, John,Lin, Zhi-Xin,Chen, Xiao-Ya,Croteau, Rodney
, p. 523 - 529 (2007/10/03)
An homology-based cloning strategy yielded a full-length cDNA from Artemisia annua that encoded a protein of 60.3 kDa which resembled a sesquiterpene synthase in sequence. Heterologous expression of the gene in Escherichia coli provided a soluble recombinant enzyme capable of catalyzing the divalent metal ion-dependent conversion of farnesyl diphosphate to β-caryophyllene, a sesquiterpene olefin found in the essential oil of A. annua. In reaction parameters and kinetic properties, β-caryophyllene synthase resembles other sesquiterpene synthases of angiosperms. The β-caryophyllene synthase gene is expressed in most plant tissues during early development, and is induced in mature tissue in response to fungal elicitor thus suggesting a role for β-caryophyllene in plant defense.
Efficient triplet-triplet energy transfer using clay-bound ionic sensitizers
Madhavan,Pitchumani
, p. 9041 - 9044 (2007/10/03)
Both cationic and anionic clays, with sensitizers anchored onto their interlayer by ionic linkage, are found to be useful 'microreactors' to achieve triplet state reactivity of myrcene in an experimentally simple, inexpensive and clean reaction. These clay-bound sensitizers are characterized by X-ray and their advantages are highlighted.
