138-86-3 Usage
Chemical Properties
Different sources of media describe the Chemical Properties of 138-86-3 differently. You can refer to the following data:
1. colourless or light yellow liquid
2. Limonene (4R)-(+)-limonene and (4S)-(?)-limonene as well as the
racemate (dipentene) occur abundantly in many essential oils.The(+)
isomer is present in citrus peel oils at a concentration of over 90%; a low concentration
of the (?) isomer is found in oils from the Mentha species and conifers.
Limonene is a liquid with lemon-like odor. It is a reactive compound; oxidation
often yields more than one product. Dehydrogenation leads to p-cymene.
Limonene can be converted into cyclic terpene alcohols by hydrohalogenation,
followed by hydrolysis. Nitrosyl chloride adds selectively to the endocyclic double
bond; this reaction is utilized in the manufacture of (?)-carvone from (+)-
limonene.
(+)-Limonene is obtained in large amounts as a by-product in the production
of orange juice; (?)-limonene is isolated in relatively small quantities from essential
oils. Racemic limonenes, which are commercially available under the name
dipentene, are formed as by-products in many acid-catalyzed isomerizations of
α- and β-pinene. Distillation of the so-called dipentene fraction yields limonenes
in varying degrees of purity.
The limonenes are used as fragrance materials for perfuming household products
and as components of artificial essential oils.
3. d-, l- or dl-Limonene has a pleasant, lemon-like odor free from camphoraceous and turpentine-like notes. Limonene
is the most important and widespread terpene; it is known in the d- and l- optically active forms and in the optically inactive dl-form
(known as dipentene).
Occurrence
It has been reported found in more than 300 essential oils in amounts ranging from 90 to 95% (lemon, orange,
mandarin) to as low as 1% (palmarosa); the most widespread form is the d-limonene, followed by the racemic form and then l-limo nene. Also reported found in ginger, nutmeg, pepper, mace, hop oil, coriander seed, calamus, dill herb, caraway seed and rosemary.
Toxicology
Different sources of media describe the Toxicology of 138-86-3 differently. You can refer to the following data:
1. D-limonene is a clear colorless mobile liquid with a pleasant lemon-like odor. （(4R)-limonene is an optically active form of limonene having (4R)-configuration. It has a role as a plant metabolite. It is an enantiomer of a (4S)-limonene.）D-limonene is one of the most common terpenes in nature. It is a major constituent in several citrus oils (orange, lemon, mandarin, lime, and grapefruit). D-limonene is listed in the Code of Federal Regulations as generally recognized as safe (GRAS) for a flavoring agent and can be found in common food items such as fruit juices, soft drinks, baked goods, ice cream, and pudding.
2. D-limonene is considered to have fairly low toxicity. It has been tested for carcinogenicity in mice and rats. Although initial results showed d-limonene increased the incidence of renal tubular tumors in male rats, female rats and mice in both genders showed no evidence of any tumor. Subsequent studies have determined how these tumors occur and established that d-limonene does not pose a mutagenic, carcinogenic, or nephrotoxic risk to humans. In humans, d-limonene has demonstrated low toxicity after single and repeated dosing for up to one year. Being a solvent of cholesterol, d-limonene has been used clinically to dissolve cholesterol-containing gallstones. Because of its gastric acid neutralizing effect and its support of normal peristalsis, it has also been used for relief of heartburn and gastroesophageal reflux (GERD). D-limonene has well-established chemopreventive activity against many types of cancer. Evidence from a phase I clinical trial demonstrated a partial response in a patient with breast cancer and stable disease for more than six months in three patients with colorectal cancer.
Uses
Different sources of media describe the Uses of 138-86-3 differently. You can refer to the following data:
1. d-Limonene is a flavoring agent that is a liquid, colorless with a pleasant odor resembling mild citrus. It is miscible in alcohol, most fixed oils, and mineral oil; soluble in glycerin; and insoluble in water and propylene glycol. It is obtained from citrus oil. It is also termed d-p-mentha-1,8,diene and cinene.
2. Limonene is an antioxidant and flavoring agent that occurs in lemons, oranges, and pineapple juice, being obtained from the oils. It is a colorless liquid which is insoluble in water and propylene glycol, very slightly soluble in glycerin, and miscible with alcohol, most fixed oils, and mineral oil. It prevents or delays enzymatic browning-type oxidation.
Definition
ChEBI: A monoterpene that is cyclohex-1-ene substituted by a methyl group at position 1 and a prop-1-en-2-yl group at position 4 respectively.
Production Methods
Limonene occurs in the oil of many plants and is the
main constituent (≤86%) of the terpenoid fraction of fruit,
flowers, leaves, bark, and pulp from shrubs, annuals, or trees
including anise, mint, caraway, polystachya, pine, lime, and
orange oil. It occurs as a by-product in the
manufacture of terpineol and in various synthetic products
made from α-pinene or turpentine oil. It is found in the gas
phase of tobacco smoke and has been detected in urban
atmospheres.
Preparation
d-Limonene may be obtained by steam distillation of citrus peels and pulp resulting from the production of juice and cold pressed oils, or from deterpenation of citrus oils; it is sometimes redistilled.
Aroma threshold values
Detection: 4 to 229 ppb
Taste threshold values
Taste characteristics at 30 ppm: sweet, orange, citrus and terpy.
Synthesis Reference(s)
Canadian Journal of Chemistry, 39, p. 1860, 1961 DOI: 10.1139/v61-249Tetrahedron Letters, 20, p. 3519, 1979 DOI: 10.1016/S0040-4039(01)95450-4
General Description
A colorless liquid with an odor of lemon. Flash point 113°F. Density about 7.2 lb /gal and insoluble in water. Hence floats on water. Vapors heavier than air. Used as a solvent for rosin, waxes, rubber; as a dispersing agent for oils, resins, paints, lacquers, varnishes, and in floor waxes and furniture polishes.
Air & Water Reactions
Flammable. Insoluble in water.
Reactivity Profile
Cinene may react vigorously with strong oxidizing agents. May react exothermically with reducing agents to release hydrogen gas.
Health Hazard
Liquid irritates eyes; prolonged contact with skin causes irritation. Ingestion causes irritation of gastrointestinal tract.
Fire Hazard
Behavior in Fire: Containers may explode.
Chemical Reactivity
Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.
Pharmaceutical Applications
Many studies have reported that D-limonene effectively plays a valuable role in the prevention of several chronic and degenerative diseases. This review provides worthy information about the beneficial effects of D-limonene such as antioxidant, antidiabetic, anticancer, anti-inflammatory, cardioprotective, gastroprotective, hepatoprotective, immune modulatory, anti-fibrotic, anti-genotoxic etc. This could in turn help in the application of D-limonene for clinical studies. Various plant families contain Terpenes as their secondary metabolites. Monoterpenes constitute an important part of these secondary metabolites. D-limonene is a well-identified monoterpene that is commonly applied as a fragrance ingredient in essential oils. D-limonene is known to possess remarkable biological activities. It can be effectively used for treating various ailments and diseases. Due to its diverse functions, it can be efficiently utilized for human health.
Numerous data on animal studies have highlighted the potential effects of D-limonene. D-limonene is well tolerated in experimental animals and protective effects of limonene were observed in several preclinical models. Animal studies showing the cardio protective and hepatoprotective effects of D-limonene are found to be inadequate. Moreover, studies exploring the anticancer efficacy of D-limonene on animal models are also found to be limited. The study on the effect of D-limonene on humans is also extremely limited. Therefore, our present review will open new avenues to undertake further research on D-limonene in preclinical models and for subjecting Cinene to effective clinical trials.
Contact allergens
Different sources of media describe the Contact allergens of 138-86-3 differently. You can refer to the following data:
1. Dipentene corresponds to a racemic mixture of d-limonene and l-limonene. Dipentene can be prepared from wood turpentine or by synthesis. It is used as a solvent for waxes, rosin and gums, in printing inks, perfumes, rubber compounds, paints, enamels, and lacquers. An irritant and sensitizer, dipentene caused contact dermatitis mainly in painters, polishers, and varnishers
2. Limonene is a racemic form of dand l-limonene.
d-Limonene is contained in Citrus species such as citrus,
orange, mandarin, and bergamot. l-Limonene is
contained in Pinus pinea. The racemic form (dand
l-limonene) is also named dipentene.
Anticancer Research
Tested as promising antitumor molecules in induced tumor on rat tissues, D-limonenewas tested in preclinical studies in patients with advanced cancer. Limonene inhibitsthe activity of HMG-CoA reductase, subsequently reducing the possibility of cancergrowth. The mechanism of action involves the inhibition of prenyltransferases withthe activation of glutathione-S transferase and uridine diphospho-glucuronosyltransferase.More interest was pointed on the principal metabolite:perillyl alcohol which is more potent than limonene. The interest on perillyl alcoholis based on the necessity of a very high dosage of D-limonene in preclinical studies(about 1000 mg/kg/day in human mammary tumor) that can cause notably importantside effects. The more active perillyl alcohol and the less low active doseshypothesized this molecule as a clinical candidate (Pattanayak et al. 2009; Chenet al. 2013; Fontes et al. 2013; Rani and Sharma 2013).
Safety Profile
A skin irritant.
Flammable when exposed to heat or flame;
can react vigorously with oxidzing
materials. When heated to decomposition it
emits acrid smoke and irritating fumes.
Carcinogenicity
Induction of kidney neoplasias
has been observed in male rats of strains that have significant
concentrations of the protein a2u-globulin (158a). This
protein is not expressed in females or species other than
the rat; therefore, limonene carcinogenicity appears to be
limited to the male of specific strains of this species.
Subcutaneous injection of the compound or its hydroperoxide
into C57BL/6 mice decreased the incidence of dibenzopyrene-
induced tumors appreciably. Given orally
either 15 min or 1 h prior to nitrosodiethylamine, D-limonene
reduced forestomach tumor formation by about 60% and
pulmonary adenoma formation by about 35%. Reduction of
cancer incidence and metastasis by limonene has also been
reported in other systems (158b).
Environmental Fate
Limonene is insoluble and is stable in water. Substances like
limonene that are monoterpenes are released in large
amounts mainly to the atmosphere. The chemical and physical
properties of limonene also indicate that limonene is
distributed mainly to air. Based on the physical and chemical
properties of limonene, when this substance is released to
ground, it has low to very low mobility in soil. The soil
adsorption coefficient (Koc), calculated on the basis of the
solubility (13.8 mg l-1 at 25 ℃) and the log octanol/water
partition coefficient (4.232), ranges from 1030 to 4780.3.
Henry’s Law constant indicates that limonene rapidly
volatilizes from both dry and moist soil; however, its strong
adsorption to soil may slow this process. In the aquatic
environment, limonene is expected to adsorb to sediment and
suspended organic particles to rapidly volatilize to the
atmosphere, based on its physical and chemical properties.
The estimated half-life for volatilization of limonene from
a model river (1 m deep, flow 1 ms-1, and wind speed
3 ms-1) is 3.4 h. The bioconcentration factor, calculated on
the basis of water solubility and the log octanol/water
partition coefficient, is 246–262, suggesting that limonene
may accumulate in fish and other aquatic organisms.
Toxicity evaluation
D-Limonene can cause a renal syndrome in male rats. Male rats
have a background of spontaneous protein droplets in the
proximal tubule, particularly within the cells of the P2 segment.
D-Limonene can increase the formation of protein droplets,
and experiments show that the only protein accumulating is
α2u-globulin. α2u-Globulin is synthesized in the liver, then it is
released into the general circulation and reabsorbed by renal
proximal tubule cells. Synthesis of α2u-globulin occurs only in
adult male rats and to understand the critical role of α2uglobulin
in the renal effects of D-limonene the absence of
histopathological changes can be studied in female rats, since
they cannot produce α2u-globulin. It was concluded from these
studies that D-limonene does not have a renal toxicity effect on
species that do not synthesize α2u-globulin, for example,
female rats, male and female mice, and dogs.
To develop nephropathy, there is a prerequisite step in
which an agent binds to α2u-globulin and in the case of
D-limonene, this agent is 1,2-epoxide. Binding of this agent to
α2u-globulin reduces the rate of degradation relative to that of
native protein, thereby causing it to accumulate. Accumulation
of α2u-globulin can be observed after a single oral dose of
D-limonene and continued treatment results in additional
histological changes in the kidney. Renal function can be
observed by increasing the amount of α2u-globulin in urine.
These functional changes occur only in male rats and only at
doses that exacerbate protein droplet formation. In response to
the cell death and functional changes, there is an increase in cell
proliferation in the kidney. With continued treatment, cell
proliferation persists but it does not restore renal function.
Increasing cell proliferation is directly related to the development
of renal tubular tumors and is dependent on the presence
of α2u-globulin. α2u-Globulin nephropathy and renal cell
proliferation occur at the same doses consistent with those that
produce renal tubular tumors.
α2u-Globulin is one type of superfamily proteins that bind
and transport a variety of agents. Many of these proteins are
synthesized in mammalian species, including humans. The
protein that can be found in human urine is very different from
that in rat urine. About 1% of the protein concentration in male
rat urine can be found in human urine. Human urinary protein
is predominantly a species of high molecular mass, and there is
no protein in human plasma or urine identical to α2u-globulin
and there is no protein-like α2u-globulin detected in human
kidney tissue. Even though the binding of D-limonene-
1,2-epoxide to α2u-globulin can be shown in vitro, other
superfamily proteins, especially those synthesized by humans,
do not bind 1,2-epoxide.
There is no verification that any human protein can
contribute to a renal syndrome similar to α2u-globulin
nephropathy, and consequently no evidence can be found that
D-limonene is carcinogenic in humans by a mechanism similar
to α2u-globulin nephropathy. The initiation of renal cell
tumors in male rats by binding to agents that act through an
α2u-globulin-associated response is not projected as a carcinogenic
hazard to humans. This can be concluded based on an
extensive evidence that the presence of α2u-globulin is an
absolute requirement for the carcinogenic activity. Therefore,
D-limonene has no carcinogenic activity in human since neither
α2u-globulin nor any protein that can function like α2uglobulin
is synthesized by humans.
Check Digit Verification of cas no
The CAS Registry Mumber 138-86-3 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 1,3 and 8 respectively; the second part has 2 digits, 8 and 6 respectively.
Calculate Digit Verification of CAS Registry Number 138-86:
(5*1)+(4*3)+(3*8)+(2*8)+(1*6)=63
63 % 10 = 3
So 138-86-3 is a valid CAS Registry Number.
InChI:InChI=1/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4,10H,1,5-7H2,2-3H3/t10-/m1/s1
138-86-3Relevant articles and documents
Generation of Br?nsted acid sites on Al2O 3-supported Ta2O5 calcined at high temperatures
Kitano, Tomoyuki,Okazaki, Shota,Shishido, Tetsuya,Teramura, Kentaro,Tanaka, Tsunehiro
, p. 189 - 196 (2012)
An alumina-supported tantalum oxide (Ta2O5/Al 2O3) calcined at 1223 K promoted both Friedel-Crafts alkylation of anisole with benzyl alcohol and isomerization of α-pinene, and exhibited Bronsted acidity despite the high temperature calcination. Among the Ta2O5/Al2O3 catalysts tested, 33 wt% Ta2O5/Al2O3 calcined at 1223 K showed the highest activity. A monolayer of tantalum acid-like compound, which has distorted octahedral symmetry, was stabilized over 33 wt% Ta 2O5/Al2O3 catalyst calcined at 1223 K. The two-dimensional Ta-O-Ta network of stabilized tantalum acid-like compound probably accounts for the generation of Bronsted acid.
A comparative study on the gas-phase and liquid-phase thermal isomerization reaction of α-pinene
He, Jindong,Gong, Yan,Zhao, Wentao,Tang, Xiangyang,Qi, Xin
, p. 15 - 22 (2013)
In this paper, a method of preparation of ocimene is investigated, which is obtained from isomerization reaction of α-pinene. Two kinds of experimental apparatus are established for the investigation of the thermal isomerization reaction of α-pinene. The behavior of thermal isomerization reaction of α-pinene is respectively discussed in the gas phase and in the liquid phase. Under gas phase conditions, the conversion of α-pinene is 80% and the selectivity of ocimene is 30%-33%. Under liquid phase conditions, the conversion of α-pinene is 60% and the selectivity of ocimene is 50%-54%. According to the kinetic-molecular theory of ideal gases, two kinds of reaction models are proposed to visualize the reaction process. In addition, the mechanism and kinetics of thermal isomerization reaction of α-pinene are respectively discussed. The conclusion is that the gas phase reaction temperature is calculated to be 390-450 °C and the liquid phase reaction temperature is calculated to be 450-550°C. From a bond dissociation energy point of view, results support the hypothesis that the reaction involves biradical intermediates. Copyright
Isomerization of α-Pinene over Immobilized AlCl3 Catalysts
Wu, Yihui,Tian, Fuping,He, Min,Cai, Tianxi
, p. 1138 - 1142 (2011)
Immobilized AlCl3 catalysts supported on γ-Al2O3 and SiO2 were prepared by a two-step vapor method and their catalytic activities were evaluated by the liquid phase isomerization of α-pinene for the first time. The results showed that the immobilized AlCl3 catalyst gave excellent catalytic performance for the isomerization of α-pinene. The AlCl3/SiO2 catalyst gave 98.4% conversion of α-pinene and 93.7% selectivity for the main products such as camphene, limonene, and terpinolene at a reaction temperature of 40 °C. The AlCl3/γ-Al2O3 catalyst gave much higher activity, 95.5% conversion of α-pinene and 94.4% selectivity for the main products even at temperatures as low as 30 °C. The excellent catalytic performance of the immobilized AlCl3 catalysts is due to their strong acidity.
Mechanistic and kinetic insights into the thermally induced rearrangement of α-pinene
Stolle, Achim,Ondruschka, Bernd,Findeisen, Matthias
, p. 8228 - 8235 (2008)
(Chemical Equation Presented) The thermal rearrangement of α-pinene (1) is interesting from mechanistic as well as kinetic point of view. Carrier gas pyrolyses with 1 and its acyclic isomers ocimene (2) and alloocimene (3) were performed to investigate the thermal network of these hydrocarbons. Kinetic analysis of the major reaction steps allows for a deeper insight in the reaction mechanism. Thus it was possible to explain the racemization of 1, the formation of racemic limonene (4), and the absence of the primary pyrolysis product 2 in the reaction mixture resulting from thermal rearrangement of 1. Results supported the conclusion that the reactions starting with 1 involve biradical transition states.
Superacidity in sulfated metal-organic framework-808
Jiang, Juncong,Gándara, Felipe,Zhang, Yue-Biao,Na, Kyungsu,Yaghi, Omar M.,Klemperer, Walter G.
, p. 12844 - 12847 (2014)
Superacids, defined as acids with a Hammett acidity function H0 ≤ -12, are useful materials, but a need exists for new, designable solid state systems. Here, we report superacidity in a sulfated metal-organic framework (MOF) obtained by treating the microcrystalline form of MOF-808 [MOF-808-P: Zr6O5(OH)3- (BTC)2(HCOO)5(H2O)2, BTC = 1,3,5-benzenetricarboxylate] with aqueous sulfuric acid to generate its sulfated analogue, MOF-808-2.5SO4 [Zr6O5(OH)3(BTC)2- (SO4)2.5(H2O)2.5]. This material has a Hammett acidity function H0 ≤ -14.5 and is thus identified as a superacid, providing the first evidence for superacidity in MOFs. The superacidity is attributed to the presence of zirconiumbound sulfate groups structurally characterized using single-crystal X-ray diffraction analysis.
Fe(NO3)3-catalyzed monoterpene oxidation by hydrogen peroxide: An inexpensive and environmentally benign oxidative process
Carari, Danieli Marcolan,Da Silva, Marcio Jose
, p. 615 - 622 (2014)
Simple Fe(NO3)2·9H2O was demonstrated to be able to catalyze the oxidation of monoterpenes by hydrogen peroxide in methyl alcohol solution. Compared with the previous iron-catalyzed methods, the present procedure avoids the use of stabilizing ligands, additives, and corrosive peroxide organic oxidants. A novel, simple and highly efficient catalyst system was developed for oxidizing monoterpenes into a valuable derivates using hydrogen peroxide, an environmentally friendly oxidant. Graphical Abstract: Possible steps involved in the Fe(III)-catalyzed oxidation of β-pinene by hydrogen peroxide into myrtenol methyl ether in methyl alcohol[Figure not available: see fulltext.]
ZrO2-SiO2 mixed oxides xerogel and aerogel as solid acid catalysts for solvent free isomerization of α-pinene and dehydration of 4-methyl-2-pentanol
Sidhpuria, Kalpesh B.,Tyagi, Beena,Jasra, Raksh V.
, p. 1164 - 1170 (2011)
Sulfated and non-sulfated ZrO2-SiO2 mixed oxide xerogel and aerogel samples having varied Zr/Si molar ratio were evaluated as solid acid catalysts for the isomerization of α-pinene and dehydration of 4-methyl-2-pentanol. Sulfation resulted into enhancement in the catalytic activity of both xerogel and aerogel samples towards the studied reactions. For example, sulfated catalysts showed 86-98% conversion of α-pinene and 8-35% conversion of 4-methyl-2-pentanol. The selectivity data for camphene and limonene indicated the requirement of moderate acidity. The correlation with cyclohexanol dehydration showed that isomerization of α-pinene is a Bronsted acid catalyzed reaction. The relationship of 4-methyl-2-pentanol conversion with acid site density and sulfur per unit area was found to be linear.
Thermolysis of α-pinene in supercritical lower alcohols
Chibiryaev,Anikeev,Yermakova,Mikenin,Kozhevnikov,Sal'nikova
, p. 987 - 992 (2006)
Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390°C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene not higher than 50%. In supercritical ethanol (430°C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).
A porous Br?nsted superacid as an efficient and durable solid catalyst
Sun, Qi,Hu, Kewei,Leng, Kunyue,Yi, Xianfeng,Aguila, Briana,Sun, Yinyong,Zheng, Anmin,Meng, Xiangju,Ma, Shengqian,Xiao, Feng-Shou
, p. 18712 - 18719 (2018)
The development of catalysts able to assist industrial chemical transformations is a topic of high importance. In view of the versatile catalytic capabilities of acid catalysts, extensive research efforts are being made to develop porous superacid materials with a high density of accessible active sites to replace molecular acid catalysts. Herein, we report the rational development of a porous Br?nsted superacid by combining important elements that target high strength acidity into one material, as demonstrated by grafting the sulfonic acid group onto a highly fluorinated porous framework, where the acid strength and stability are greatly enhanced by an electron-withdrawing environment provided by the polymer backbone, reminiscent of that seen in Nafion resin. In addition, the densely arranged acid groups that are confined in the three-dimensional nanospace facilitate the transfer of hydrons, thereby further increasing the acidity. By virtue of the pore structure and strong acidity, this system exhibits excellent performance for a wide range of reactions, far outperforming commercial acid resins under repeated batch and flow reaction conditions. Our findings demonstrate how this synthetic approach may instruct the future design of heterogeneous acid catalysts with advantageous reaction capabilities and stability.
Biochemistry and molecular genetics of the biosynthesis of the earthy odorant methylisoborneol in Streptomyces coelicolor
Wang, Chieh-Mei,Cane, David E.
, p. 8908 - 8909 (2008)
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
