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Mentha × Piperita L. or peppermint belonging to the family Lamiaceae (mint) is an important herb and useful in pharmaceutical, medicinal and cosmetic industries. In this study, the interactive effe...

The base-free transfer hydrogenation (THR) of menthone with six aliphatic alcohols as hydrogen source has been developed under sub- and supercritical conditions. Under sc conditions (at 350 °C and 78–210 atm) without any catalyst, all alcohols demonstrated the similar H-donor activity, which was high enough. The menthone conversion was about 64 ± 5% for 5 h of the reaction, whereas the selectivity on menthol reached 92–99% for all alcohols except MeOH (73%). The non-catalytic THR at 250 °C was very slow and the conversion in the most active 2-PrOH was only 7.0–7.5% for 9 h of the reaction. Under subcritical conditions at 150 °C, the non-catalytic menthone reduction was negligible in all alcohols. But in secondary 2-PrOH and 2-BuOH, the base-free THR catalyzed by Raney® nickel results in excellent conversion and selectivity of menthol at 150 °C, whereas no conversion of menthone was observed in primary alcohols under the same reaction conditions. A quasi-equilibrium of isomeric menthone/isomenthone mixture reached via enolization was evaluated under sub- and supercritical conditions and the Gibbs energies of the isomerization in each alcohol were calculated.

Rheumatoid arthritis (RA) is an autoimmune disease with nearly 1.6 billion patients worldwide and an incidence of 0.5-1%. In recent years, basic and clinical studies have revealed that immune cell responses and corresponding secretion of inflammatory factors are important in the control of RA development. Our study found that a natural plant ingredient, menthone, could be used as a potential antirheumatism compound.

The catalytic properties of the industrial “palladium on sibunit” catalyst (ICT-3-31, 0.5 wt % Pd) were studied in the reduction of menthone into menthol. Menthone was reduced both at 250 and 350°C using isopropanol as an H-donor under the conditions of the hydrogen transfer reaction (HTR). For comparison, a noncatalytic reaction was performed under the same conditions. At 350°C the conversion of menthone was the same (61–62%) in the presence of the catalyst and without it. In the reaction with the catalyst, the selectivity on the desired product menthol decreased considerably (from 98% down to 23%), and the amount of the by-products increased (from 2 up to 77% based on changed menthone). When the temperature of the catalytic reaction was lowered to 250°C, the reduction selectivity increased to 42%, but the conversion of menthone decreased to 10%. All the products of menthone conversion were identified and pathways of their formation suggested. At 250–350°C the carbon support sibunit catalyzed the dehydration of menthone, which hindered the satisfactory yields of the target alcohol. Other side reactions catalyzed by ICT-3-31 were dehydrogenation into p-menthenes and their further aromatization resulted in the formation of substituted benzenes—p-cymene and thymol. ICT-3-31 can be effectively used in HTR, if more reactive organic substrates are involved in the reaction below 200–250°C or stronger H-donors are applied.

Menthone is rich in Mentha × Piperita L. essential oil and it has anti-inflammatory properties; research shows that it is useful, via percutaneous absorption, in treating inflammation-related diseases. However, anti-allergic inflammatory effects of volatile menthone have not yet been used to treat allergic asthma, in vivo. We hypothesized that menthone inhalation may have anti-inflammatory and anti-allergic effects in patients with allergic asthma. Therefore, in our study, menthone inhalation was used to treat ovalbumin (OVA)-sensitized and challenged asthmatic mice. Allergic inflammation mediator changes in the lungs and airways, sera, splenocytes, and peritoneal macrophages of the mice were measured. Relative expression amounts of six receptor genes related to allergic inflammation of the lungs and airways were quantitated using a two-step real time quantitative polymerase chain reaction (qPCR). Results showed that menthone inhalation increased serum OVA-specific IgG2a/IgG1 and IgG2a/IgE ratios, increased Th1-type cytokine production in the bronchoalveolar lavage fluid, and decreased nitric oxide, protein, and eotaxin levels. Menthone inhalation inhibited mast cell and eosinophil degranulation, and chemokine (C-C motif) receptor 3 (Ccr3) gene expression amounts, but (relatively) increased Th1 cytokine secretion by splenocytes. Our results evidence that menthone inhalation alleviates local and systemic allergic inflammation in asthmatic mice.

Efficient syntheses of two potentially useful optically active macroheterocycles with esters and dihydrazides of 2,6-pyridinedicarboxylic and adipic acids starting from available natural L-menthol and passing through intermediate 8-hydroxy-2,6R-dimethyloctan-3-one were developed. The key steps were [2 + 1]-reaction of the last with 2,6-pyridinedicarboxylic acid chloride and [1 + 1]-condensation of the resulting α,ω-diketodiester with 2,6-pyridinedicarboxylic- and adipic-acid dihydrazides. The structures were confirmed using IR and NMR spectroscopy and LC-MS.

Suspension particle assisted solvent sublation was designed for the first time. The volatile monoterpenes in Mentha haplocalyx Briq were extracted using this method from a solution containing plant solid particles as the lower phase of solvent sublation. Under the optimum conditions of the solvent sublation (n-hexane/plant solid particles 20% ethanol-water solution system, pH 4, flotation time 30 min and air flow rate 30 mL/min), the extraction yields were 2.0 × 10

Conversion of pulegone in CO2 can suit as an alternative method to synthesis of menthone, carvone or thymol. The use of high-density carbon dioxide in the catalytic conversion of pulegone, for the first time, was investigated over 0.5 wt% Pd, or Rh, or Ru supported on alumina via hydrogenation allowing to eliminate use of organic solvent. It was possible to achieve various key natural flavour products with high selectivity and conversion. Reaction catalysed by all the catalysts was faster in a single supercritical phase (fluid reagents) than in a biphasic system (liquid + fluid reactants). The reaction catalysed by Pd produced fully hydrogenated C C isomers of menthone with a selectivity above 98% in a short time of 15 min. The Rh catalyst was found to be more active and selective towards thymol's formation (99.8%). The Rh catalysed reaction exhibited >98% selectivity of thymol with the conversion of >98% after a 75 min reaction. A 25 min-reaction with the Ru catalyst converted pulegone in 99% to carvone with a 99.4% selectivity. High conversion and diverse and high selectivity accompanied by beneficial reduction in reaction time depending on the catalyst used are achieved in CO2 applied compared to those reported for conventional organic solvents used.

Two regioisomeric lactams, which are derived from terpenoid ketone (−)-menthone in two steps, are oligomerized in an easy acid-induced procedure to obtain oligoamides that contain alkyl groups and stereocenters; for this, a nucleophilic oligomerization via a non-ionic propagating site (neutral conditions) and a polycondensation are also possible. Furthermore, a regioselective synthesis is demonstrated where (−)-menthone is transformed into one of these lactams in a one-step procedure via Beckmann rearrangement without isolation of any oxime intermediate using the reagent hydroxylamine-O-sulfonic acid (HOSA). These concise oligoamide syntheses smooth the way to novel sustainable long-chain polyamides with highly interesting structures.

Danshu capsule (DSC) is a medicinal compound in traditional Chinese medicine (TCM). It is commonly used for the treatment of acute & chronic cholecystitis as well as choleithiasis. To study its choleretic effect, healthy rats were randomly divided into DSC high (DSCH, 900mg/kg), medium (DSCM, 450mg/kg), and low (DSCL, 225mg/kg) group, Xiaoyan Lidan tablet (XYLDT, 750mg/kg), and saline group. The bile was collected for 1h after 20-minute stabilization as the base level, and at 1h, 2h, 3h, and 4h after drug administration, respectively. Bile volume, total cholesterol, and total bile acid were measured at each time point. The results revealed that DSC significantly stimulated bile secretion, decreased total cholesterol level and increased total bile acid level. Therefore, it had choleretic effects. To identify the active components contributing to its choleretic effects, five major constituents which are menthol (39.33mg/kg), menthone (18.02mg/kg), isomenthone (8.18mg/kg), pluegone (3.31mg/kg), and limonene (4.39mg/kg) were tested on our rat model. The results showed that menthol and limonene could promote bile secretion when compared to DSC treatment (p > 0.05); Menthol, menthol and limonene could significantly decrease total cholesterol level (p

A platform of starch complexes for the oral release of aroma substances by salivary fluids was studied. Menthone, menthol and limonene were used as model flavor compounds for complexation with starches with different amylose content. Complexes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic light scattering (DLS), and atomic force microscopy (AFM). Aroma retention was tested under pH, temperature and storage challenges. Furthermore, the kinetic of aroma release in simulated saliva fluids (SSF) was also tested. Both menthone and menthol form V-amylose complexes in a ’food grade’ process while limonene does not form such complexes efficiently. Complexation yield was higher, with more included aroma and less free core content, as the amylose content increased. The complexes had melting temperature of over 90 °C. Digestion results suggest that the complexes can release the aroma in the oral cavity.

Features of the Wittig olefination reaction of menthone lactol and its aluminate by several n-alkylidenetriphenylphosphoranes were studied. The product of the reaction with ethylidenetriphenylphosphorane was used in the synthesis of the sex pheromone of peach leaf miner Lyonetia clerckella.

International audience; Cycloaddition reactions between a menthone-based chiral nitrone and alkenes or alkynes under microwave activation afforded a series of enantiopure cycloadducts in good yields and with high stereoselectivity. Removal of the chiral auxiliary under acid-catalysis led to a new series of isoxazolidines and isoxazolines with the control of one, two or three stereogenic centers.

During a program dedicated to the biocatalytic access of structurally useful α-hydroxy ketones, we made the unexpected observation that epoxy enol acetates derived from (+)- and (–)-menthone stereoselectively rearranged on exposure to silica through a diastereoselective process, providing easy access to the complete set of α-hydroxymenthone stereoisomers. The absolute configurations of the four stereoisomers were unambiguously established by IR-VCD and X-ray diffraction, thus clarifying some literature discrepancy. Two of the four stereoisomers could also be obtained through astereoconvergent process, thus avoiding the inherent 50 % yield limitations of such diastereoselective reactions. A solvent-free version allowing an extremely rapid reaction (< 2 h) is also described. Finally, the observed diastereoselection was investigated by DFT calculations.

Asymmetrical oxidation was performed of menthone dithiolane obtained in 95–98% yield by condensation of menthone with 1,2-ethanedithiol in the presence of boron trifluoride etherate. 6-Isopropyl-9-methyl-1,4-dithiaspiro[4,5]decane-1,4-dioxide (yield 5–55%) and 6-isopropyl-9-methyl-1,4-dithiaspiro[4,5]-decane-1,1,4-trioxide (yield 65–70%) were synthesized. Chemical structures of compounds obtained were proved by XRD analysis, NMR and IR spectroscopy.

Electroreduction of an equilibrium menthone-isomenthone mixture at a controlled potential in a diaphragm cell on various cathodes was studied. The influence exerted by the nature of a solvent and of an electrode, electrode material, and various additives on the reduction stereoselectivity of ketones was examined. Conditions for a predominant formation of the most stable of the four isomeric alcohols being formed, menthol, were found.

meta-Chloroperoxybenzoic acid (m-ClPBA) was shown to be an oxidant for two stereoisomers of menthone oxothiolane. The effect of steric factors on the ability to oxidize the sulfide group was found. Oxidation of (5S,6S,9R)-6-isopropyl-9-methyl-1-oxo-4-thiaspiro[4.5]-decane to the sulfone was prevented by the steric proximity of an isopropyl group to the S atom in the oxothiolane ring.

The helical twisting powers of the E-isomers of aldol condensation products of menthone and aromatic aldehydes are higher than those of the Z-isomers. In order to find out which chiral centre of these menthone derivatives is responsible for the value of the helical twisting in both isomers, the E-isomers of aldol condensation products of 3-methylcyclohexanone and 2-isopropylcyclohexanone were prepared and photoisomerized to form Z-isomers. The physical properties of these species were determined. It was concluded that the strong helical twisting power of the E-isomers of the derivatives of menthone is caused by the chiral carbon atom containing the methyl group in the ring. The relatively low helical twisting power of the Z-isomers and the composition of the E-Z isomers in the photostationary state are determined mainly by the other chiral centre containing the isopropyl group.

Starting from (−)-menthone, a new chiral building block useful for liquid crystal preparation was synthesized. This chiral moiety was attached to selected phenols under mild conditions by esterification. Rigid cores of tolanebenzoates and phenylbenzoates were prepared using the palladium cross-coupling reaction or by traditional liquid crystal synthesis methods. This convergent approach ended with a second esterification or palladium cross-coupling reaction to furnish new liquid crystal materials with smectic A, smectic C* and N* phases, as well as blue phases (BP). Thermal behavior, and the effect of chiral moiety branches and molecular packing in the smectic phases, have been investigated using differential scanning calorimetry, optical microscopy and X-ray diffraction.

Polymeric chiral reductants selective for the reduction of (−)-menthone 1 to the diastereomeric products (−)-menthol 2 and (+)-neomenthol 3 were prepared by a covalent molecular imprinting using 2 as the template. The LiAlH4 derivatized imprinted polymers altered the natural outcome of the reduction reaction (LiAlH4) from 2:1 [(−)-menthol:(+)-neomenthol] to 1:1. The reaction mechanism is discussed in terms of reaction site structure. The molecularly imprinted polymers demonstrated enantioselective recognition for 2 (0.15 μmol enantioselective sites/g polymer) in batch binding experiments.

The addition of cyanomethyl lithium to (−)-menthone at −78°C followed by 1.5 h stirring at room temperature and acidic workup produced exclusively the axial addition product, being the first example of preferred axial attack of an organometallic reagent to menthone. In the case of hydrolysis at −78°C after 0.5 h reaction time the equatorial addition product was isolated as the preferably formed isomer. The axial and equatorial cyanomethyl substituted menthol and neomenthol, respectively, were isolated in high yields.

In the current contribution the optimization of menthol and menthone isolated from food and pharmaceutical samples by solid-phase microextraction (SPME) will be presented. Extraction efficiencies for commercial (polydimethylsiloxane) and laboratory-made (ethoxypolydimethylsiloxane) coated quartz fibers were compared. The results show, that SPME coupled with GC–flame ionisation detection is a reproducible method for isolation and for qualitative and quantitative determination of menthol and menthone at ppm as well as ppb levels. The described procedure can be recommended for routine food and pharmaceutical analyses.

The constituents of the volatile oil of air-dried aerial parts of Mentha pulegium L. (Lamiaceae) plants wildly growing in Northwest Iran were analysed by GC/MS. 46 components were identified, comprising 96.6% of the essential oil. Monoterpenes (78.9%) were the main class of the identified components followed by a minor proportion of sesquiterpenes (11%). Oxygenated monoterpenes (75.3%) were the major subclass of volatile oil components with menthone (38.7%), menthol (11.3%), neomenthol (10.5%), and pulegone (6.8%) as major compounds. Sesquiterpene hydrocarbons (10.6%) were the highlighted subclass of 15 carbons sesquiterpenoidal compounds with (E)-caryophyllene (4.9%) and ß-cubebene (2.5%) as their principle representatives. Furthermore, menthyl acetate (C 12 acetylated monoterpene derived compound) was contained considerable amounts (5.2%) in the essential oil. In total, volatile oil composition of M. pulegium L. plants studied in the present experiment was characterised as a new menthone type with appreciable amounts of menthol and neomenthol, and it could be used as a potential source of these high value monoterpenes in pharmaceutical and food industries.

The activation of (−)-menthone with anhydrous CeCl3 led to high yielding additions of different organometallic reagents. Products of exclusively equatorial-addition of the reagents were obtained; only PhMgBr yielded additionally ca. 5% of the axial-addition product.

Stereoselective hydrogenation of (R)-(+)-pulegone and (2S,5R)-(−)-menthone over Raney nickel at room temperature with dilute and concentrated alkali in presence of β-cyclodextrin and its derivatives was studied. The effect of alkali and β-cyclodextrin and its derivatives on the modification of the yield and the proportion of epimeric alcohols formed were found to be the salient features of this reaction ( Scheme. 1 Download : Download high-res image (29KB) Download : Download full-size image Scheme. 1 . ).

A study aimed at defining a molecular arrangement where a chiral fragment derived from menthone or camphor transfers its central chirality to a 2,2'-biphenol residue, inducing an axial chirality, is reported. The menthol or isoborneol groups are attached at the two benzylic positions at 3,3' in order to maximize efficiency in practical applications. A reliable and high-yielding procedure for the synthesis of such C(2)-symmetric molecules substituted at the 3,3'-positions has been developed. The procedure entails Mannich condensation with paraformaldehyde and morpholine, protection of the hydroxylic functions, chlorination, metalation, and addition to (-)-menthone and (+)-camphor. The use of samarium diiodide is essential in the latter step for optimum selectivity and efficiency. The tetrols exhibit intramolecular hydrogen bonding between phenolic and alcoholic hydroxy functions within each monomeric unity, so that they retain their rotational freedom. NOEDS and COSY experiments show that the tetrols are present in more than one rotamer. The tetrols react with tetrachlorosilane to afford siloxanes as pure diastereoisomers, showing that the metal is able to induce preferential helicity at the biphenyl residue; i.e., the central chirality of menthol or isoborneol auxiliary is totally transfered to the axial chirality of the biphenyl. The configurations could be determined by NOEDS and heterocorrelated HMQC experiments. Remarkably, while the menthol derivative induces total M helicity, the camphor induces complementary P helicity. These results suggest that these tetrols may be useful as ligands in catalysts for asymmetric synthesis.

In the presence of β-cyclodextrin and its derivatives, the hydrogenation reaction of (2 S ,5 R )-(−)-menthone proceeded smoothly with high stereoselectivity for the formation of (1 R ,2 S ,5 R )-menthol.

Procedures are developed for the preparation of menthone oxime esters as accessible perfumes and fragrant additives synthesized from natural raw materials.

A new approach for the preparation of photosensitive materials for coloured data recording and storage is advanced. This approach involves the synthesis of copolymers containing nematogenic and combined (-)-arylidene-p-menthan-3-one chiral photochromic fragments in one monomer unit. The conditions for the formation of an LC phase in the chiral photochromic homopolymers as a function of the structure of the side groups have been identified; for a new series of copolymers, the effect of their composition on the phase behaviour and photooptical properties is considered. Planarly oriented films of the copolymers show selective light reflection in the UV, visible, and near IR spectral regions. The photochemical behaviour of the homopolymers and copolymers in dilute solution and as films has been studied. In these systems, under UV radiation, the E-Z isomerization of the (-)-arylidene-p-menthan-3-one fragment is the dominating process. The kinetic features of the photoprocess are revealed, and the effective qua...

The synthesis of new chiral calix[n]arenes, related to Corey's phenyl-menthol, is described. Starting from enantiomerically pure (R)-(+)-pulegone, calix[n]arenes with different ring sizes could be obtained in reasonable yield.

Functionalised optically active bicyclo[4.3.0] system 5 , and angularly fused tricyclo [7.4.0.0 4.9 ] system 11 were synthesized from ( l )-menthone propargyl derivative 4 and spiromenthone propargyl derivative 10 by tin-mediated radical cyclization. © 1997 Elsevier Science Ltd.

The effect of P_cyclodextrm (BCD) and its methyl and polymer denvatlves on the stereoselectlve reduction of menthone was studied Modlficatron of the yield and the proportion of eplmenc alcohols formed were found to be the salient features of this reactlon Reduction of menthone m aqueous solution m presence of heptakls-2,6-d+O-methyl-Pcyclodextnn (DMBCD) remarkably enhanced the yield to 68% (from 10%) resultmg m a menthol/neomenthol ratio of 1 2 5 Aqueous DMF ( 1 1) as the solvent mcreased the yield from 14 0% m water to 76% m the presence of BCD, the menthol/ neomenthol ratlo bemg 1 3 6 Under phase transfer condltlon, DMBCD m water-benzene mixture gave 82 0% yield along with a good stereoselectlvlty compared to 47 0% m the absence of a phase transfer catalyst

X-ray diffraction analysis proved that the stereochemical configuration of interaction products of (−)-menthone with aromatic aldehydes (α,β-unsaturated ketones or β-hydroxyketones) depends on the generation conditions of intermediate enolate carbanions. In irreversible deprotonation of (−)-menthone with strong sterically hindered organometallic bases, products of interaction with aldehydes preserve the 1R,4S-configuration; in equilibrium conditions, 1R,4R-diastereomers of the corresponding α,β-unsaturated ketones are formed with high stereoselectivity.

By acetalisation of L-menthone (2) with mercaptoacetic acid and derivatives of benzylamine, the spirocyclic N,S-acetals 3 were obtained as single diastereomers. The reaction of an epimeric mixture of unsubstituted thiazolidinones 4 with acetic anhydride or allyl iodide afforded homochiral N-acetyl (5) or N-allyl N,S-acetals (6), respectively. The configuration of the new stereogenic centres were proven by X-ray crystallography.

A three-step procedure for the synthesis of chiral annulated indenes is described in which nopinone, verbenone and menthone are converted to their enolate form, alkylated with 2-bromomethylbromobenzene, ring-closed with CrCl 2 /cat. NiCl 2 and dehydrated with catalytic acid.

Asymmetrical oxidation was performed of menthone dithiolane obtained in 95–98% yield by condensation of menthone with 1,2-ethanedithiol in the presence of boron trifluoride etherate. 6-Isopropyl-9-methyl-1,4-dithiaspiro[4,5]decane-1,4-dioxide (yield 5–55%) and 6-isopropyl-9-methyl-1,4-dithiaspiro[4,5]-decane-1,1,4-trioxide (yield 65–70%) were synthesized. Chemical structures of compounds obtained were proved by XRD analysis, NMR and IR spectroscopy.

Three (6a – c) of the four conceivable diastereomeric 1-ferrocenylalkylamines can be synthesized from I-(−)-menthone and ferrocene in high enantiomeric purity. The many potential applications of such compounds, including their use as chiral templates in diastereoselective four component condensations (4CC, Ugi Reaction) are examined. Furthermore, NMR evidence for the first example of up-down-isomerism, a new type of conformational stereoisomerism of ferrocene derivatives, is discussed.

The two diastereomers of spirocyclic 5,6-dimethyl-4H-1,3-dioxin-4-one (5,6) have been synthesized by acetalization of tert-butyl 2-methyl-3-oxobutanoate (2) with (-)-menthone (4). Their structures have been determined by NMR analysis.

Three (6a – c) of the four conceivable diastereomeric 1-ferrocenylalkylamines can be synthesized from I-(−)-menthone and ferrocene in high enantiomeric purity. The many potential applications of such compounds, including their use as chiral templates in diastereoselective four component condensations (4CC, Ugi Reaction) are examined. Furthermore, NMR evidence for the first example of up-down-isomerism, a new type of conformational stereoisomerism of ferrocene derivatives, is discussed.

Regioisomeric lactones (ee98%) were obtained by microbiological Baeyer-Villiger oxidation of enantiomers of menthone and dihydrocarvone. The regioselectivity of the biotransformation is shown to be dependant upon the considered enantiomer. An improvement of our empirical model of the active site is suggested.

The aim of the current study was to investigate the metabolism of (-)-menthone by liver microsomes of humans. (-)-Menthone (1) was metabolized to (+)-neomenthol (2) (3-reduction) and 7-hydroxymenthone (3) by human liver microsomes. The metabolites formed were analyzed on GC and GC-MS. Kinetic analysis showed that K(m) and V(max) values for the metabolized (-)-menthone to respective (+)-neomenthol and 7-hydroxymenthone by liver microsomes of human sample HG70 were 0.37 mM and 4.91 nmol/min/mg protein and 0.07 mM and 0.71 nmol/min/mg protein.

Asymmetric Michael addition of (S)-menthone imine of ethyl glycinate to ethyl acrylate had been investigated under PTC conditions using solid base and different kinds of PT catalysts. The reaction gave adducts of enantiomeric excesses of 5–47%.

Asymmetric Michael addition of (S)-menthone imines of glycinates to alkyl acrylates can be performed in solid base conditions. The reactions gave adducts in yields of 40–60% and enantiomeric excesses of 23–45%. The results are best explained by a cyclic transition state mechanism.

Enantiodifferentiating transformation of prochiral diols possessing σ-symmetry was realized by the utilization of titanium tetrachloride-promoted selective ring-cleavage reaction of spiroacetals derived from the diols and I-menthone with allyltrimethylsilane.