Cyclic Terpenes Research Articles

Diurnal cycle of emission of induced volatile terpenoids by herbivore-injured cotton plant.

Cotton plants attacked by herbivorous insect pests emit relatively large amounts of characteristic volatile terpenoids that have been implicated in the attraction of natural enemies of the herbivores. However, the composition of the blend of volatile terpenes released by the plants varies remarkably throughout the photoperiod. Some components are emitted in at least 10-fold greater quantities during the photophase than during the scotophase, whereas others are released continuously, without conforming to a pattern, during the entire time that the plants are under herbivore attack. The diurnal pattern of emission of volatile terpenoids was determined by collecting and analyzing the volatile compounds emitted by cotton plants subjected to feeding damage by beet armyworm larvae in situ. The damage was allowed to proceed for 3 days, and volatile emission was monitored continuously. During early stages of damage high levels of lipoxygenase-derived volatile compounds [e.g., (Z)-3-hexenal, (Z)-3-hexenyl acetate] and several terpene hydrocarbons [e.g., alpha-pinene, caryophyllene] were emitted. As damage proceeded, high levels of other terpenes, all acyclic [e.g., (E)-beta-ocimene, (E)-beta-farnesene], were emitted in a pronounced diurnal fashion; maximal emissions occurred in the afternoon. These acyclic terpenes followed this diurnal pattern of emission, even after removal of the caterpillars, although emission was in somewhat smaller amounts. In contrast, the emission of cyclic terpenes almost ceased after the caterpillars were removed.

Conformational analysis of cyclic terpenes: application of computational and experimental (NMR) methods

The solution structure of the cyclic diterpene cembrene was investigated. A strategy for conformational analysis is proposed which is based on computational and experimental (NMR) methods. By a non-systematic, random exploration of torsional angles under ring-closing constraints a search for favourable low-energy conformers is accomplished and their energy is minimized. According to several criteria of equality, groups of “equal” structures are formed. Steady-state nuclear Overhauser effects and vicinal coupling constants are calculated for the group representatives. For the evaluation of the most probable solution structure, which is based on these parameters, rather than the structures themselves, calculated and experimentally determined values are compared. As a result the conformer which corresponds to the lowest energy structure proposed by computational methods alone fits best with experimental parameters and strongly dominates the solution structure of cembrene.

Interactions of cyclic hydrocarbons with biological membranes.

Many cyclic hydrocarbons, e.g. aromatics, cycloalkanes, and terpenes, are toxic to microorganisms. The primary site of the toxic action is probably the cytoplasmic membrane, but the mechanism of the toxicity is still poorly understood. The effects of cyclic hydrocarbons were studied in liposomes prepared from Escherichia coli phospholipids. The membrane-buffer partition coefficients of the cyclic hydrocarbons revealed that these lipophilic compounds preferentially reside in the membrane. The partition coefficients closely correlated with the partition coefficients of these compounds in a standard octanol-water system. The accumulation of hydrocarbon molecules resulted in swelling of the membrane bilayer, as assessed by the release of fluorescence self-quenching of fluorescent fatty acid and phospholipid analogs. Parallel to the expansion of the membrane, an increase in membrane fluidity was observed. These effects on the integrity of the membrane caused an increased passive flux of protons and carboxyfluorescein. In cytochrome c oxidase containing proteoliposomes, both components of the proton motive force, the pH gradient and the electrical potential, were dissipated with increasing concentrations of cyclic hydrocarbons. The dissipating effect was primarily the result of an increased permeability of the membrane for protons (ions). At higher concentrations, cytochrome c oxidase was also inactivated. The effective concentrations of the different cyclic hydrocarbons correlated with their partition coefficients between the membrane and aqueous phase. The impairment of microbial activity by the cyclic hydrocarbons most likely results from hydrophobic interaction with the membrane, which affects the functioning of the membrane and membrane-embedded proteins.

Long‐range proton spin‐spin coupling in rigid cyclic structures by 2D NMR/‘through‐space coupling’

AbstractIn H,H COSY spectra of rigid cyclic terpenes, many long‐range couplings can be observed. The coupled nuclei are connected either by a zig‐zag coupling path or they are close in space. The latter are called ‘through‐space’ coupling. A certain stereospecific relationship between the coupling partners is necessary. This phenomenon is in accordance with the theoretical explanations.

The preparation of the (6R)- and (6S)-diastereoisomers of 5-formyltetrahydrofolate (leucovorin)

The separation of the (6R)- and (6S)-diastereoisomers of tetrahydrofolic acid by derivatisation on N-5 with chiral auxiliary reagents followed by fractional crystallisation or extraction is described. Chloroformates of chiral alcohols were used as chiral auxiliaries and those derived from cyclic terpene alcohols were found to be most effective for the separation. The cleavage of the derivative and conversion in situ into 5,10-methenyltetrahydrofolic acid which was subsequently hydrolysed to afford 5-formyltetrahydrofolate (leucovorin) was investigated for the derivatised tetrahydrofolates; that from (–)-menthol was the only one that combined satisfactory separation with sufficient lability for efficient conversion into 5-formyltetrahydrofolate. The characterisation and optical purity of the products is described.

Geraniol, Linalool, Thymol and Carvacrol-rich Essential Oils from Monarda Hybrids

ABSTRACT Monarda fistulosa L., var. menthaefolia, native to southern Manitoba, was crossed with M. didyma, and through a series of open pollination and selection cycles, winter-hardy disease-resistant hybrids were generated. The volatile constituents of essential oil from these hybrids were analyzed by GC and GC/MS. The volatile concentrates obtained by nitrogen extraction contained high levels of cyclic terpenes including α-pinene and camphene. The volatile composition of oil extracted by hydrodistillation varied significantly among different hybrids. The oil of one hybrid contained geraniol(>92%), oil of a second hybrid contained carvacrol (73.5%), oil of a third hybrid contained linalool (67%), oil of a fourth hybrid contained thymol (31%) and oil of a fifth hybrid contained 1, 8-cineole (22%). The corresponding oil yields obtained by hydrodistillation were 1.17, 1.08, 1.0, 0.62 and 0.68 g/100 g of fresh plant tissue, respectively.

Terpenes and the lipid-protein-partitioning theory of skin penetration enhancement.

A series of terpenes has been assessed as skin penetration enhancers towards the model polar penetrant 5-fluorouracil (5-FU). Cyclic terpenes were selected from the chemical classes of hydrocarbons (e.g., alpha-pinene), alcohols (e.g., alpha-terpineol), ketones (e.g., carvone), and oxides (e.g., 1.8-cineole, ascaridole). Permeation experiments were performed on excised human epidermal membranes and the terpenes varied in their activities; alpha-pinene only doubled the permeability coefficient of aqueous 5-FU, whereas 1.8-cineole caused a near 95-fold increase. Essential oils, e.g., chenopodium (70% ascaridole), were less effective than the corresponding isolated terpenes, 5-FU is less soluble in the terpenes than in water, and the terpenes did not exert their action by increasing partitioning of the drug into the membranes as illustrated by stratum corneum:water partitioning studies. The penetration enhancers increased drug diffusivity through the membranes, an effect which correlated empirically with the enhancer activities. The principal mode of action of these accelerants may be described by the lipid-protein-partitioning theory: the terpenes interacted with intercellular stratum corneum lipids to increase diffusivity, and the accelerant effects were not due to partitioning phenomena. Keratin interaction was assumed negligible.

ChemInform Abstract: Chiral Isoprenyl Ethers from 3‐Ethoxy‐2‐methylacrolein by Vinylogous Transesterification and Wittig Alkenylation.

AbstractThe title ether (IIIb), synthesized starting from the reaction of the ketone (I) with the chiral alcohol (II), may be used as starting material for the preparation of cyclic terpenes.

ChemInform Abstract: Complete Structural Analysis of Cyclic Polyhalogenated Monoterpenes. A Force Field 2D‐NMR Study.

The information obtained from two-dimensional NMR and NOED spectroscopy led to the complete structural analysis of five cyclic monoterpenes of marine origin. Correlated 2D spectra allowed the establishment of the gross structural features, the final stereochemical assignments being made by NOEDS. The use of 13C NMR shifts in defining the regio- and stereochemistry of monoterpenes 17–21 is criticized in terms of the inappropriateness of the models used. Force field calculations show that models 8–16 do not accurately reproduce the structural features of the cyclic terpenes 17–21, thus precluding the straightforward application of 13C additive effects. The calculated minimum energy conformers of 17–21 agree well with the geometries deduced experimentally by using a generalized Karplus equation. © 1986, American Chemical Society. All rights reserved.

Chirale Isoprenylether aus 3‐Ethoxy‐2‐methylacrolein durch vinyloge Umesterung und Wittig‐Alkenylierung

Chiral Isoprenyl Ethers from 3‐Ethoxy‐2‐methylacrolein by Vinylogous Transesterification and Wittig AlkenylationChiral isoprenyl ethers 5 as potential starting materials for enantioselective syntheses of cyclic terpenes are shown in a model reaction to be prepared by vinylogous transesterification of 3‐ethoxy‐2‐methylacrolein (1) with chiral alcohols such as (R)‐ and (S)‐1,2‐O‐isopropylideneglycerol 2 and subsequent Wittig alkenylation of the resulting chiral 3‐alkoxy‐2‐methylacroleins 3.

Microbial allyl rearrangement and resolution of acetates of unsaturated cyclic terpene alcohols by Pseudomonas sp. NOF-5 strain.

Microbial hydrolysis of the acetates of unsaturated cyclic terpene alcohols by Pseudomonas sp. NOF-5 isolated from soil was investigated. (±)-trans-Carveyl acetate ((±)-trans-3) was enantioselectively hydrolyzed with NOF-5 strain to give (-)-trans-carveol ((-)-trans-2 of 86.6% optical purity). However, the hydrolysis of (±)-cis-3 was less enantioselective, while (±)-piperitylacetate ((±)-6, a cis and trans mixture) was hydrolyzed to give the (-)-trans- and (-)-cis-piperitols ((-)-trans-5 and (-)-cis-5) in a poor optical yield. In this case, other tert-alcohos, (+)-trans- and (-)-cis-2-p-menthen-1-ols ((±)-trans-7 and (-)-cis-7), were also produced. Furthermore, microbial and enzymic allyl rearrangements of (+)-trans-6 and (-)-trans-verbenylacetate ((-)-trans-11) were studied. Biological treatment of (+)-trans-6 and (-)-trans-11 with NOF-5 or its esterase gave (+)-trans- and (-)-cis-7 and (+)-cis-3-pinen-2-ol ((+)-cis-12), respectively.

Hydrolysis of bismetallic complexes of linalyldiphosphate and their participation in the biosynthesis of cyclic monoterpenes

The allylic diphosphate ester linalyldiphosphate forms mono- and bis-metallic complexes with Mg2+ and Mn2+. Complexes of the trianion of the ligand are 50 to 100 times more stable than those of the dianion. Mg2+ and Mn2+ are bound in the monometallic complex 103 and 104 times more strongly than in the bismetallic species.The rate constant of the uncatalysed hydrolysis of linalyldiphosphate at pH 7.0 is 1.2 × 104s–1, which is higher than reported values for the primary diphosphates. Mg2+ and Mn2+ affect its rate of hydrolysis and it is shown that the rate enhancement observed is a function of the concentration of the bismetallic complexes.The rate of cyclic terpene hydrocarbon biosynthesis catalysed by carbocyclase from Citrus limonum also correlates with the concentration of the bismetallic complexes.Linalyl monophosphate, which is not a substrate for carbocyclase hydrolyses at a rate proportional to the concentration of the monometallic complex of Mn2+. The neutral charge of this complex, as opposed to the positively charged bismetallic complex of linalyl diphosphate may be an explanation of the absence of utilization of this complex as a substrate.It appears from the data presented and from previous evidence that bismetallic complexes of allylic diphosphates are the most reactive species in their hydrolysis and the only reactive species in the enzymic cyclization of these precursors of monoterpenes.

Synthesis of monoterpene hydrocarbons from [1- 3H]linalyl pyrophosphate by carbocyclase from Citrus limonum

A partially purified enzyme preparation from the flavedo of Citrus limonum utilized [1- 3H]linalyl pyrophosphate as a substrate for cyclic terpene hydrocarbon formation more efficiently than the pyrophosphates of nerol and geraniol. The products formed from all three substrates are α-pinene, β-pinene, limonene, and γ-terpinene. Neryl and geranyl pyrophosphate inhibit the formation of these products from linalyl pyrophosphate. No free linalyl pyrophosphate could be detected during the enzymatic formation of cyclic terpene hydrocarbons from geranyl pyrophosphate. Mn 2+ catalyzes the nonenzymatic solvolysis of linalyl pyrophosphate, forming myrcene and ocymenes and no bicyclic hydrocarbons. Linalyl pyrophosphate is a sterically plausible precursor of cyclic hydrocarbons, but the present data support only its role as an alternative substrate and not as an obligatory free intermediate in terpene biosynthesis.

Enzymic resolution of (.+-.)-unsaturated cyclic terpene alcohols via asymmetric hydrolysis of corresponding acetates by microorganisms.

Asymmetric hydrolysis of the acetates of (±)-cis and trans-carveols by microorganisms or their esterase produced chiral cis and trans-carveols and the acetates of their enantiomers. The enantioselectivity of the microbial hydrolysis and the optical purities of the products varied with the species of microorganisms. This method was also applied in separation of diastereomeric mixtures of (−)-carveols and (−)-7-epi-α-cyperols.

ChemInform Abstract: SELECTIVE REACTIONS WITH ORGANOALUMINUM COMPOUNDS

AbstractReview: Anhand nachstehender Beispiele wird ein Überblick über die Entwicklung selektiver Reaktionen mit Organo‐ Al‐Verbindungen gegeben.

Selective Reactions with Organoaluminum Compounds

AbstractWith the aid of selected examples an overview is given of the development trends in highly discriminative reactions using organoaluminum compounds. (1) Isomerization of substituted oxiranes into allyl alcohols has been effected both stereo‐ and regioselectively by means of a new organoaluminum reagent, diethylaluminum 2,2,6,6‐tetramethylpiperidide (DATMP); this reaction which provides a new route for the regiospecific transformation of allyl alcohols into 1,3‐dienes. (2) A novel nonenzymic heterolysis of allylic phosphates of terpenoids has been effected by organoaluminum compounds and has enabled development of a new method for the selective synthesis of cyclic terpenes. (3) The reductive condensation of α‐haloketones with carbonyl compounds in the presence of diethylaluminum chloride and zinc affords β‐hydroxy‐carbonyl derivatives in good yields with exclusion of undesired self‐condensations products.

Essential oil Composition of Ceratocystis virescens

SUMMARYThe essential oil of Ceratocystis virescens was analyzed by means of gas and thin-layer chromatography, infrared spectrometry, mass spectrometry and chemical means. The oil from C. virescens was compared for chemotaxonomic purposes with that of C. variospora. The major constituents in the oil of C. virescens were: 6-methyl-5-hepten-2-ol acetate, linalool and geranyl acetate. One cyclic terpene, a-terpineol, was isolated.

Essential Oil Composition of Ceratocystis Virescens

SUMMARY The essential oil of Ceratocystis virescens was analyzed by means of gas and thin-layer chromatography, infrared spectrometry, mass spectrometry and chemical means. The oil from C. virescens was compared for chemotaxonomic purposes with that of C. variospora. The major constituents in the oil of C. virescens were: 6-methyl-5-hepten-2-ol acetate, linalool and geranyl acetate. One cyclic terpene, a-terpineol, was isolated.

Optically active amines. XX. Application of the salicylidenimino chirality rule to cyclic terpene amines

Optically active amines. XX. Application of the salicylidenimino chirality rule to cyclic terpene amines

The Evolution of the Alarm-Defense System in the Formicine Ants

1. The higher formicine ants base their chemical alarm-defense systems primarily on a limited array of acyclic terpenes discharged from the mandibular glands, and alkanes and ketones discharged from Dufour's gland. All of these substances appear to be utilized in defense, and most, especially those at the lower end of the range of molecular weight (C9-C13), also function as alarm pheromones. The active space of the pheromones reaches over a distance of centimeters and is relatively short-lived. The alarm response of the various species can be classified roughly as either "panic" or "aggressive" in nature. 2. Two major adaptive alterations in the basic alarm-defense system have occurred within the higher Formicinae. In the genus Acanthomyops, the mandibular gland has been enlarged and made the site of storage of unusually large quantities of citronellal and two isomers of citral. We suggest that the changes are causally linked to the development of a strongly aggressive form of alarm communication. The response thresholds are also higher than in the one species (Lasius alienus) displaying a panic form of communication for which similar measurements have been taken. Lasius subgenus Chthonolasius, which is considered phylogenetically intermediate between Acanthomyops and the more primitive Lasius subgenus Lasius, also has an intermediate set of alarm-defense chemicals. Lasius subgenus Dendrolasius has evolved a system similar to that of Acanthomyops, except that cyclic terpenes (furans) are the substances produced in excess. 3. The second major adaptive change has occurred in certain species of the slave-making Formica sanguinea group. In these ants the Dufour's glands have been enlarged to become the site of large quantities of decyl, dodecyl, and tetradecyl acetates. The acetates are highly effective alarm substances, with extensive, long-lived active spaces. When discharged at target colonies during slave raids, they also alarm and help disperse the defending workers. Thus they serve both as a colonial signal and as an offensive form of "propaganda."