Enantiomers Of Α-pinene Research Articles

Chromatographic Evaluation of the Composition of Essential Oil and α-Pinene Enantiomers in Juniperus communis L. Berries during Ripening

Chromatographic assessment of the composition of the essential oils of Juniperus communis was carried out to measure enatiomeric distribution of α-pinene in the two plant morphotypes and to determine if harvesting time possesses the effect on the content of individual components in the oil. The major compound in the studied juniper berries was α-pinene (26.8–42.7%). There were no significant differences in the α-pinene content between the two analyzed morphotypes. The second quantitative component in the analyzed oils of unripe and ripe berries was myrcene, whose amounts differed in the studied morphotypes. Consequently, myrcene may be used as one of the indicators discriminating two different juniper chemotypes. The results obtained clearly indicate that the plants belong to two different chemotypes, producing very stable proportions of (1R)-(+) and (1S)-(–)-α-pinene enatiomers at all harvesting periods. The ratio of (1R)-(+) and (1S)-(–) enantiomers was 6.4–8.0 in the oils from morphotype with light-green berries and 2.0–2.2 in the oils from morphotype with bluish-green berries.

Addition products of chlorosulfonylisocyanate to (+)-3-carene and α-pinene enantiomers

Optically active lactams were synthesized from (+)-3-carene and α-pinene enantiomers. Their properties and structures were characterized. A pathway for preparing their trifluoroacetate salts was demonstrated.

Ozonolysis of α-PINENE, β-PINENE, d- and l-Turpentine Oil Studied by Chirooptical Methods; Some Implications on the Atmospheric Chemistry of Biogenic Volatile Organic Compounds

The main constituents of biogenic volatile organic compounds (BVOC) released in the atmosphere from vegetation are terpenes. The most common terpenes are α-pinene and β-pinene. These molecules react with ozone, forming oxidized derivatives which have low vapor pressure and which nucleate into secondary organic aerosol (SOA). Such aerosol-forming reactions have been simulated in the gas phase on laboratory scale with the visualization of the formation of SOA. Electronic absorption spectroscopy shows that the UV peak of pinenes at 205 nm is shifted to 225 nm during and after ozonolysis and is accompanied by a series of spectral features in the near infrared region (between 850 nm and 1100 nm). Optical rotatory dispersion (ORD) spectra were recorded on pure β(+)pinene and β(−)pinene. After ozonolysis β-pinene enantiomers are converted into nopinone enantiomers. The ORD spectra of both (−)nopinone and (+)nopinone respectively were recorded. The former showed a peak at 453 nm, an inflection point at 430 nm and a trough at 405 nm. The ORD spectrum of (−)-nopinone appears completely symmetrical to that of (+)nopinone. Thus, ORD spectroscopy can distinguish between BVOC and oxidized BVOC quite easily at least in the case of β-pinene. The ORD spectra of α-pinene enantiomers are different from those of β-pinene enantiomers and although the ORD spectra of ozonized α-pinene are not easily distinguishable from those of the primary compounds, they are completely different from those of ozonized β-pinene enantiomers. A reasonable natural model of BVOC is offered by l- and d-turpentine oil whose composition reflects that of the BVOC from conifer forests. The ORD spectra of ozonized l- and d-turpentine has permitted to distinguish between the levorotatory and dextrorotatory oxidation products and showing the ketone peak at about 367–380 nm, thus permitting in a real model to distinguish between primary BVOC (turpentine) and oxidized BVOC (or SOA) corresponding to ozonized turpentine. It has been proposed that ORD spectra in the gas phase could be used to detect chiral BVOC and oxidized chiral BVOC.

Gamma-radiolysis of chiral terpenes: α-(−)pinene and α-(+)pinene

The terpenes α-(+)-pinene, and α-(−)pinene have been radiolyzed at radiation doses of 150, 300 and 600 kGy. The radiolyzed samples have been analyzed by FT-IR spectroscopy and polarimetry. Both α-(+)-, α-(−)-pinenes show a linear trend to radioracemization as a function of the radiation dose administered ≈2.5·10−3 [α]D/kGy. The solvent fractionation and the liquid chromatographic analysis (HPLC) of the radiolyzed samples shows that both α-pinene enantiomers produce ocimene and dipentene together with minor quantities of other products and a resin. The kinetics of α-pinene decomposition under radiolytic conditions can be described by a pseudofirst order rate constant k∼5.3·10−7s−1 while the radiation chemical yield for the same reaction has a G = 5.0 molecules/100 eV, so that about 30% of the original α-pinene is converted into other products at 600 kGy.

CDNA isolation, functional expression, and characterization of (+)-α-pinene synthase and (−)-α-pinene synthase from loblolly pine ( Pinus taeda): Stereocontrol in pinene biosynthesis

The complex mixture of monoterpenes, sesquiterpenes, and diterpenes that comprises oleoresin provides the primary defense of conifers against bark beetles and their associated fungal pathogens. Monoterpene synthases produce the turpentine fraction of oleoresin, which allows mobilization of the diterpene resin acid component (rosin) and is also toxic toward invading insects; this is particularly the case for α-pinene, a prominent bicyclic monoterpene of pine turpentine. The stereochemistry of α-pinene is a critical determinant of host defense capability and has implications for host selection, insect pheromone biosynthesis, and tritrophic-level interactions. Pines produce both enantiomers of α-pinene, which appear to arise through antipodal reaction mechanisms by distinct enzymes. Using a cDNA library constructed with mRNA from flushing needles of loblolly pine ( Pinus taeda), we employed a homology-based cloning strategy to isolate, and confirm by functional expression, the genes encoding (+)-(3 R:5 R)-α-pinene synthase, (−)-(3 S:5 S)-α-pinene synthase, and several other terpene synthases. The pinene synthases, which produce mirror-image products, share only 66% amino acid identity (72% similarity) but are similar in general properties to other monoterpene synthases of gymnosperms. The stereochemical control of monoterpene cyclization reactions, the evolution of “antipodal” enzymes, and the implications of turpentine composition in ecological interactions are discussed.

The kinetics, stereochemistry, and deuterium isotope effects in the α-pinene pyrolysis. Evidence for incursion of multiple conformations of a diradical

Pyrolysis of optically active α-pinene gave 95% racemic limonene (dipentene), alloocimine, racemic α-pinene, α-pyronene. Activation parameters are reported. Pyrolysis of ( S) syn-6-trideuteriomethyl α-pinene at 256.7°C for 2400 s gave dipentene with twice as much deuterium as hydrogen transfer with k H/ k D=1.49 and alloocimine with a Z and E trideuteriomethyl ratio of ca. 5 with k H/ k D=0.89. The isotope effect on loss of starting material was 1.16. Separation of the enantiomers of α-pinene from 3600 s pyrolyses at 256.7°C followed by NMR analysis revealed that the ratio of the R- syn to R- anti to S- anti isomers is 4.6:3.7:1 at roughly two half-lives. Kinetic analysis reveals that the previously proposed mechanism for all conversions involving slow interconversion of two diradicals with C s symmetry is not consistent with the distribution of the α-pinene isomers, particularly the formation of more suprafacial-retention product ( R- anti) than bond-rotated isomer ( S- anti). Inclusion of another C s species (ignoring the deuteriums) that would be intermediate between the originally proposed C s species, appears more consistent with the observations.

Influence of organic solvent on the behaviour of camphor and α-pinene enantiomers in reversed-phase liquid chromatography systems with α-cyclodextrin as chiral additive

Reversed-phase liquid chromatography has been applied in order to gain insight into the α-cyclodextrin (α-CD)–solute complexation process, which occurs in the aqueous mobile phases containing a secondary achiral modifier. The model compounds tested were (±)-camphor and (±)-α-pinene. Methanol, ethanol, and 1 or 2-propanol were used as secondary modifiers. Retention factors and enantioseparation factors have been determined on a RP 18 stationary phase as a function of the α-CD concentration, secondary modifier content, and temperature changes. The shortest retention and the best separation of studied compounds were achieved for aqueous–methanol eluents. Apparent stability constants in various binary aqueous–organic solvent mixtures have been evaluated for α-CD complexes of camphor enantiomers. Using the competition concept, values for the stability constants in pure water have been calculated. It has been found that: (1) the quotient of the stability constants for both enantiomers, denoted as absolute enantioselectivity E, always remains constant at a fixed value ( E≅1.9), which may indicate that the complex composition does not change, (2) only the first step in the complexation process is altered by changing the solvent, which does not seem to affect the separation of the enantiomers, (3) the remarkable enantioselectivity that is observed results from the second step in the complexation process, (4) enthalpy changes are much more favourable for camphor–α-cyclodextrin complex formation than for the transfer of camphor to the stationary phase, which means that complexation dominates over adsorption and retention is shorter at lower temperatures, (5) the difference in free energy changes of complexation (ΔΔ G) between the enantiomers of camphor is about 1.5 kJ/mol at 20°C.

NMR manifestations and molecular dynamics modeling of chiral recognition of α-pinenes by α-cyclodextrin

NMR manifestations of chiral recognition of α-pinene enantiomers by α-cyclodextrin in D2O have been observed in both proton and carbon spectra. The largest splittings in the former spectra amounted to 0.06ppm while an unusually high value of 1.3ppm was found in the corresponding carbon spectra. Different mobilities of the enantiomeric guests in the host cavities have been established in D2O using NOE and ROESY techniques. Molecular dynamics simulations indicated the instability of the complexes of 1:1 stoichiometry both in vacuum and water. However, the corresponding calculations for the 1:2 stoichiometry in vacuum gave incorrectly larger stability of the complex with the (1R,5R)-enantiomer of α-pinene. Long simulations of 3.5ns in water reproduce the stability order of the diastereomeric complexes.

Response of parasitoids Dendrosoter protuberans and Cheiropachus quadrum to attractants of Phloeotribus scarabaeoides in an olfactometer.

The braconid Dendrosoter protuberans and the pteromalid Cheiropachus quadrum are two parasitoids of the olive bark beetle, Phloeotribus scarabaeoides. Several chemicals such as α-pinene, β-pinene, 2-decanone, 2-nonanone, decanal, undecanal, and n-butyl acetate have been identified as attractants in the laboratory for this scolytid. Under red light at 27°C in a laboratory olfactometer both parasitoids oriented positively to both enantiomers of α-pinene, and females also responded to 2-decanone. Significant responses did not occur under white light or at lower temperatures. These results suggest that α-pinene and 2-decanone could be involved in the location of P. scarabaeoides by its parasitoids. Consequently an attracticidal control tactic for this scolytid that included these chemicals could eliminate part of the parasitoid population. In an integrated pest management program, this problem should be considered.

Differences in Bioactivity between the Enantiomers of α-Pinene

Many terpenes used therapeutically or as flavor and fragrance materials are chiral compounds. Chiral separations have been advocated for the identification of adulteration of commercial oils as different essential oils and synthetic components contain different proportions of each enantiomer. An alternative method of assessing enantiomeric composition and thereby adulteration was tested using several biological parameters versus the bioactivity of the enantiomers of α-pinene. It was found that 18 out of 25 different bacteria were more affected by the (−) enantiomer of α-pinene; 19 out of 20 different L. monocytogenes strains were affected more by the (+) isomer and two of three filamentous fungi were affected more by the (+) enantiomer. The (−) enantiomer was more spasmogenic on smooth muscle than the (+) enantiomer. This suggests that differing bioactivities can indicate adulteration and also that medicaments containing chiral components should be formulated using the most suitable enantiomeric forms for each particular medical condition.

Kinetics of reaction of chlorine atoms with some biogenic organics

The reaction kinetics of atomic chlorine with a series of biogenic hydrocarbons, including the two enantiomers of α-pinene, were studied at 298 K and 1 atm pressure using a relative rate technique. The simultaneous losses of the biogenic of interest and a reference compound, either n-nonane or n-butane, were followed using gas chromatography with flame ionization detection as a function of the extent of photolysis of a chlorine atom precursor. Thionyl chloride, trichloroacetyl chloride or in a few trials, acetyl chloride, were photolyzed at 254 nm to generate chlorine atoms, since molecular chlorine reacted in the dark with these organics. The relative rate constants for ethane and isoprene determined relative to n-butane using SOCl2 and CCl3COCl were compared to those determined using Cl2 to check for possible artifacts. The average relative rate constants for ethane and isoprene (both relative to n-butane) using these new sources are (0.281 ± 0.021) and (2.49 ± 0.39) (±2 σ) respectively, within experimental error of those measured using Cl2 as the chlorine atom source. The relative rate constants averaged over all sources including Cl2 are (0.277 ± 0.025) for ethane and (2.42 ± 0.45) for isoprene. The ratios of rate constants for the chlorine atom reactions with the biogenics with formula C10H16 relative to n-nonane were as follows: (R)-α-pinene (0.991 ± 0.264); (S)-α-pinene (0.946 ± 0.240); β-pinene (1.09 ± 0.30); (R)-limonene (1.33 ± 0.15); myrcene (1.36 ± 0.31); 3-carene (1.16 ± 0.23). That for p-cymene, C10H14, is (0.433 ± 0.072). Taking k(Cl + n-nonane) = (4.82 ± 0.14) × 10−10 cm3 molecule−1 s−1, the absolute rate constants (in units of 10−10 cm3 molecule−1 s−1) are: (R)-α-pinene (4.8 ± 1.3); (S)-α-pinene (4.6 ± 1.2); β-pinene (5.3 ± 1.5); limonene (6.4 ± 0.8); myrcene (6.6 ± 1.5); 3-carene (5.6 ± 1.3); p-cymene (2.1 ± 0.4). (All errors are ± 2 σ). Although abstraction was not measured directly in this study, it is likely a significant contributor to the overall reactions of the C10H16 biogenics. The rate constant for the reaction of the aromatic compound p-cymene is within experimental error of that predicted from the sum of reaction with toluene plus the isopropyl substituent. A limited number of experiments for methyl vinyl ketone in N2 using CCl3COCl as the chlorine atom source and nonane as the reference compound gave a relative rate constant of (0.422 ± 0.034), corresponding to an absolute rate constant of (2.0 ± 0.2) × 10−10 cm3 molecule−1 s−1. Based on these rate constants, the lifetimes of these biogenics at dawn with respect to reaction with chlorine atoms are expected to be comparable to reaction with OH. Thus, loss of these biogenics by reaction with atomic chlorine must be taken into account in coastal regions in addition to their reactions with OH, O3 and at night, NO3. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 491–499, 1999

Differences in bioactivity between the enantiomers of α-pinene and limonene

Differences in bioactivity between the enantiomers of α-pinene and limonene

Measurement of Vibrational Circular Dichroism below ∼600 cm−1: Progress towards Meeting the Challenge

The measurement of vibrational circular dichroism (VCD) below ∼600 cm−1 is one of the experimental challenges of the current times. Polarization-division interferometry is considered to be the most efficient approach for realizing these measurements. A crucial component for successful applications of this interferometry is the beamsplitter, which divides the incoming beam according to polarization. Free-standing metal wires and the metal wires deposited on a mylar substrate have been employed as beamsplitters, and their performance has been evaluated for the ∼700–10 cm−1 region. VCD measurements obtained for the enantiomers of α-pinene in the 400–250 cm−1 region are presented. The current status and future developments needed for routine far-infrared VCD measurements are summarized.

Chromatographic studies of the enantiomeric composition of some therapeutic compositions applied in the treatment of liver and kidney diseases

A gas-liquid chromatographic system with α-cyclodextrin in formamide medium (coated on Chromosorb) was used for the separation of enantiomers of α-pinene, β-pinene, limonene and camphene in medicines applied in the therapy of liver and kidney diseases. The drugs under investigation were produced in Poland (Terpichol and Terpinex), in Germany (Rowachol and Rowatinex) and in Slovenia (Uroterp). It was found that, depending on the manufacturer, medicines possessing similar chemical compositions differ considerably from one another regarding the content of enantiomers, mainly those of α-pinene.

Stereochemistry of the Proton Elimination in the Formation of (+)- and (−)-α-Pinene by Monoterpene Cyclases from Sage (Salvia officinalis)

The three pinene synthases (cyclases) from common sage (Salvia officinalis) catalyze the conversion of geranyl pyrophosphate to the bicyclic olefins (+)-α-pinene and (+)-camphene (cyclase I), (−)-α-pinene, (−)-β-pinene, and (−)-camphene (cyclase II), and (+)-α-pinene and (+)-β-pinene (cyclase III), in addition to smaller amounts of monocyclic and acyclic monoterpene olefins. (1R)-4-2H1-and (1S)-4-2H1-labeled geranyl pyrophosphates were prepared and used to examine the stereochemistry of the C3-proton elimination from the pinyl cation intermediates in the formation of the α-pinene enantiomers. Mass spectrometric analysis of the biosynthetic products derived from the chirally deuterated substrates revealed that cyclase I and cyclase III removed the C4-proR-hydrogen of the substrate (C3 proton trans to the dimethyl bridge of the pinyl nucleus) with a stereoselectivity exceeding 94% in the formation of (+)-α-pinene. Similarly, cyclase II removed the C4-proS-hydrogen of the substrate (C3-trans proton of the corresponding pinyl cation) with a stereoselectivity exceeding 78% in the formation of (−)-α-pinene. The stereoselectivity of these C3-axial hydrogen eliminations is rationalized on the basis of a stereochemical model for the electrophilic isomerization-cyclization reaction sequence catalyzed by the pinene cyclases. The changes in the overall rates of olefin biosynthesis by these enzymes and in the product ratios resulting from deuterium substitution also permitted confirmation of isotopically sensitive branching in pinene biosynthesis and allowed the observation of primary kinetic isotope effects in isolation.

Stereospecific antennal response by red turpentine beetle,Dendroctonus valens to chiral monoterpenes from ponderosa pine resin

The antennal response ofDendroctonus valens to host monoterpenes from the resin of ponderosa pine was studied using the electroantennogram (EAG) technique. Male and female beetles were given a single dose of each of 11 different monoterpenes. Response amplitude to the different compounds did not vary between sexes and was generally well correlated with results from field attraction studies. Response to (S)-(-)-β-pinene was greatest. The relative amplitude of the responses to the (R)-(+) and (S)-(-) enantiomers of a-pinene, however, were reversed from their relative attractiveness in the field. A dose-response study was conducted for the (R)-(+) and (S) -(-) enantiomers of a-pinene, plus a reciprocal differential saturation test with successive doses of first one enantiomer ofα-pinene and then the other. Comparison of EAG traces suggests different receptors for the two stereoisomers ofα-pinene. Differential saturation curves suggest that while one set of receptors may respond to both enantiomers, some receptors respond only to the (S)-(-) enantiomer.

New metabolites of α-pinene produced by the mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Scolytidae)

Emergent females of the mountain pine beetle, Dendroctonus ponderosae, contained five previously undetected volatiles: toluene, 4-methylene-6,6-dimethylbicyclohept-2-ene (verbenene), p-mentha-1,5,8-triene, o- and p-cymene. Exposure of wild or axenically reared beetles to protio- and deuterio-α-pinene or protio- and deuterio- trans-verbenol indicated that all compounds except toluene were produced from α-pinene, with trans-verbenol as a probable intermediate. The ratio between these α-pinene metabolites was insensitive to the level of α-pinene to which the beetles were exposed, suggesting a tightly regulated enzymatic and/or acid-catalyzed conversion of α-pinene. Exposure of females to either enantiomer of α-pinene or to the same amount of (±)-α-pinene indicated that female mountain pine beetles possess two enantiospecific enzyme systems for processing α-pinene. Production of p-cymene constitutes the first record in an insect of an aromatic volatile produced from a monoterpene hydrocarbon.

Method Synthesizes Chiral Boranes In 100% Optical Purity

Chemists at Purdue University have developed a method to hydroborate olefins to chiral boranes in 100% optical purity [J. Am. Chem. Soc., 106, 1797 (1984)]. Processes already exist to convert such boranes to alcohols, amines, and halides, as well as to homologous alcohols, aldehydes, ketones, carboxylic acids and esters, nitriles, cis- and trans-olefins, and acetylenes. Thus the new technique opens routes to absolutely stereospecific synthesis of compounds of nearly every type. In addition, the method regenerates the α-pinene used to induce chirality by a simple displacement, making it almost catalytic in nature and useful for largescale preparations. Moreover, because both enantiomers of α-pinene are available commercially, chemists can choose in advance what chirality the product will have. There were two keys to the success of the technique. First, organic chemistry professor Herbert C. Brown and postdoctoral student Bakthan Singaram discovered that the 2:1 adduct of isopinocampheylborane and tetrameth...