Isomeric Alcohols Research Articles

Synthesis and determination of the absolute configuration of (-)-(5R,6Z)-dendrolasin-5-acetate from the nudibranch Hypselodoris jacksoni.

A small sample of (−)-(5R,6Z)-dendrolasin-5-acetate, which was fully characterized by 2D NMR studies, was isolated from the nudibranch Hypselodoris jacksoni, along with the sesquiterpenes (+)-agassizin, (−)-furodysinin, (−)-euryfuran, (−)-dehydroherbadysidolide and (+)-pallescensone. A synthetic sample ([α]D −8.7) of the new metabolite was prepared by [1,2]-Wittig rearrangement of a geranylfuryl ether followed by acetylation of purified alcohol isomers. The absolute configuration at C-5 was established as R by the analysis of MPA ester derivatives of (Z)-5-hydroxydendrolasin obtained by preparative enantioselective HPLC.

Searching for radical intermediates and pathways implied in the biosynthesis of some polycyclic cembranoids. A new plausible mechanism for the origin of sinulanocembranolide A in the coral Sinularia gyrosa

The 3(2H)-furanone 11 underwent dimerisation to 13 (71%) via the captodative radical intermediate 12 on treatment with t-butyl hydroperoxide, but similar treatment of 5-episinuleptolide (5) failed to produce the natural product 7 via the presumed radical intermediate 8. In other attempts to generate 8, irradiation of a solution of 5 in benzene led only to the corresponding E-isomer 14, and treatment of 5 with Mn(OAc)3 in HOAc produced the acetate of the isomeric alcohol 15. However, when a solution of 5-episinuleptolide (5) in THF was reacted with samarium diiodide, a sequence of transannular ketyl radical-induced coupling reactions ensued leading to the ring fused compound 20 in 62% yield. From these experiments in vitro it is difficult to make the case for the involvement of carbon-centred radical intermediates suggested earlier, in the biosynthesis of some polycyclic norcembranoids. It is proposed that the ring system in the recently described sinulanocembranolide A (1) is derived in vivo by way of a novel (3+2) type (possibly 1,3-dipolar) transannular cyclisation from the enedione intermediate 23 produced from 5-episinuleptolide (5).

The Volatile Profiles of a Rare Apple (Malus domesticaBorkh.) Honey: Shikimic Acid‐Pathway Derivatives, Terpenes, and Others

The volatile profiles of rare Malus domestica Borkh. honey were investigated for the first time. Two representative samples from Poland (sample I) and Spain (sample II) were selected by pollen analysis (44-45% of Malus spp. pollen) and investigated by GC/FID/MS after headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE). The apple honey is characterized by high percentage of shikimic acid-pathway derivatives, as well as terpenes, norisoprenoids, and some other compounds such as coumaran and methyl 1H-indole-3-acetate. The main compounds of the honey headspace were (sample I; sample II): benzaldehyde (9.4%; 32.1%), benzyl alcohol (0.3%; 14.4%), hotrienol (26.0%, 6.2%), and lilac aldehyde isomers (26.3%; 1.7%), but only Spanish sample contained car-2-en-4-one (10.2%). CH2 Cl2 and pentane/Et2 O 1 : 2 (v/v) were used for USE. The most relevant compounds identified in the extracts were: benzaldehyde (0.9-3.9%), benzoic acid (2.0-11.2%), terpendiol I (0.3-7.4%), coumaran (0.0-2.8%), 2-phenylacetic acid (2.0-26.4%), methyl syringate (3.9-13.1%), vomifoliol (5.0-31.8%), and methyl 1H-indole-3-acetate (1.9-10.2%). Apple honey contained also benzyl alcohol, 2-phenylethanol, (E)-cinnamaldehyde, (E)-cinnamyl alcohol, eugenol, vanillin, and linalool that have been found previously in apple flowers, thus disclosing similarity of both volatile profiles.

PATCHOULI ALKOHOL ISOMERS POGOSTEMON HERBA PREDICTED VIRTUALLY

The aim of our research is predicting the alpha-patchouli alcohol isomer Pogostemon Herba as inhibitors cyclooxygenase (COX-1 and COX-2) isoenzymes. The data for the alpha-patchouli alcohol isomer (CD521903, CD442384, and/or CD6432585) Pogostemon Herba were explored from the pubchem database. Molecular interaction studies with COX-1 and COX-2 from mouse were done using the molecular docking tools Hex 6.12 and LeadIT2 Bisolve. The analysis of the alpha-patchouli alcohol compounds of patchouli oil showed that alpha-Patchouli alcohol (CD521903) binds to COX-1 at active sites including: LEU223B, ASP228B, LEU237B, ARG 332B, TRP 138A, GLU 139A, SER 142A, ASN 143A, and the interaction to COX-2 at active site including: GLN 289B, GLU 290B, ARG 222B, LYS 211B, THR 212B, HIS 214B, ASN 382B, HEM682B, GLN 454B, HIS 386B, TRP 387B, HIS 388B, VAL 274B, GLN 203B, VAL 291B, VAL 295B. The interaction hydrogen bond energy between alpha-patchouli alcohol: (CD521903-COX-1 complexes (-4 kJ/mol) and CD521903-COX-2 complexes (-8 kJ/ mol) by LeadIT2 Biosolve. This suggests alpha-patchouli alcohol CD521903 as candidate for a selective COX-2 inhibitor. These in silico data need further analyses of biological function activity.

The Influence of Molecular Structure and Aerosol Phase on the Heterogeneous Oxidation of Normal and Branched Alkanes by OH

Insights into the influence of molecular structure and thermodynamic phase on the chemical mechanisms of hydroxyl radical-initiated heterogeneous oxidation are obtained by identifying reaction products of submicrometer particles composed of either n-octacosane (C28H58, a linear alkane) or squalane (C30H62, a highly branched alkane) and OH. A common pattern is observed in the positional isomers of octacosanone and octacosanol, with functionalization enhanced toward the end of the molecule. This suggests that relatively large linear alkanes are structured in submicrometer particles such that their ends are oriented toward the surface. For squalane, positional isomers of first-generation ketones and alcohols also form in distinct patterns. Ketones are favored on carbons adjacent to tertiary carbons, while hydroxyl groups are primarily found on tertiary carbons but also tend to form toward the end of the molecule. Some first-generation products, viz., hydroxycarbonyls and diols, contain two oxygen atoms. These results suggest that alkoxy radicals are important intermediates and undergo both intramolecular (isomerization) and intermolecular (chain propagation) hydrogen abstraction reactions. Oxidation products with carbon number less than the parent alkane's are observed to a much greater extent for squalane than for n-octacosane oxidation and can be explained by the preferential cleavage of bonds involving tertiary carbons.

Virtual screening of compounds from the patchouli oil of Pogostemon herba for COX-1 inhibition

Our interest is to identify compounds from the patchouli oil of Pogostemon herba to inhibit the cyclooxygenase-1 (COX-1) enzyme activity. The data for the major compounds (alpha-patchouli alcohol isomer (CD521903, CD442384, and/or CD6432585), alphabulnusene, seychellene and alpha-guaiene) of patchouli oil were explored from the PubChem database. The compounds to COX-1 interactions were studied using the molecular docking tools Hex 6.12 and LeadIT2 Bisolve. The interactions were further visualized using the Chimera 1.7s viewer software tool. The analysis of the major compounds of patchouli oil showed that alpha-Patchouli alcohol (CD521903) binds to COX-1 at many active sites including: Leu223B, Asp228B, Leu237B, Arg332B, Trp138A, Glu139A, Ser142A, and Asn143A. Further analysis revealed that these binding sites are maintained by hydrogen bonds with Ser142A, Glu139A, and Asp228B. The interaction energy between COX-1 and alpha-patchouli alcohol (CD521903) is -6 kJ/mol (without solvent) and -15 kJ/ mol (with solvent DMSO). These theoretical data suggests alpha-patchouli alcohol as a potential inhibitor of the COX-1 enzyme. However, these observations should be investigated and confirmed using experimental evidence.

Extraction of vanadium(V) from acid solutions with octyl alcohol isomers

Vanadium(V) extraction with octyl alcohol isomers from acid solutions was studied. Two areas are determined, wherein the vanadium(V) extraction in relation to acidity of the aqueous phase is maximal. The opposite effects of temperature on the extraction are found. The mechanism of the vanadium(V) extraction with high molecular weight alcohols from weakly acid solutions was suggested.

Theoretical characterization of gas-phase thermolysis products of ethane-1,2-diol, 2-chloroethanol and 2-fluoroethanol

The transition structures and the activation energies for the possible thermal elimination of H2O, HF and HCl from ethane-1,2-diol, 2-fluoroethanol and 2-chloroethanol respectively, were investigated. The relative stabilities and associated barrier heights of syn and anti vinyl alcohol isomers and their acetaldehyde tautomer were estimated. HF, DFT/B3LYP and MP2 methods at 3-21G, 6-31+G(d), 6-311++G(d,p) and aug-cc-pvdz basis sets were applied to identify the stationary points of the studied systems. The optimized geometries and electronic energies of reactants, transition states and products were analyzed. The dependence of these properties upon the theoretical level was discussed. A concerted proton release and a hydroxide or halide ion expulsion mechanism was proposed to account for the thermal rearrangement of reactants to products. A thorough understanding of syn vinyl alcohol preference is provided by performing natural bond orbital (NBO) analysis. The oxygen atom lone pair (LP) and periplanar hyperconjugative effects are responsible for this preference. It was suggested that the LP hyperconjugative interactions with the C=C σ and π antibonds were the most important origin of the structural differences between the two vinyl alcohol isomers.

High temperature ignition delay times of C5 primary alcohols

Ignition delay times of the three C5 primary alcohol isomers (n-pentanol, iso-pentanol and 2-methyl-1-butanol) were measured behind reflected shock waves. Experiments were conducted in the temperature range of 1100–1500K, pressures of 1.0 and 2.6atm, equivalence ratios of 0.25, 0.5 and 1.0, and O2 concentration in the fuel/O2/Ar mixtures varying from 3.75% to 15%. Measurements show that the ignition delay time and the global activation energy of the three isomers both decrease in the order of iso-pentanol, 2-methyl-1-butanol, and n-pentanol. Chemical kinetic mechanisms for n-pentanol (Mech NP) and iso-pentanol (Mech IP), recently developed by Dagaut and co-workers, were used to model the respective ignition delay times. Results show that Mech NP yields close agreement at the equivalence ratio of 0.25, but the agreement is moderated with increasing equivalence ratio. Mech IP yields fairly close agreements at relatively higher temperatures but over-predicts the measurements by 50% at relatively lower temperatures for the three equivalence ratios studied. A new 2-methyl-1-butanol high temperature mechanism was proposed and validated against the ignition delay data. Sensitivity analysis for both n-pentanol and iso-pentanol showed the dominance of small radical reactions. Reaction pathway analysis aided further scrutiny of the fuel-specific reactions in Mech NP, leading to refinement of the kinetic model, and improved agreement between the predicted and measured ignition delay times as well as the jet-stirred reactor results.

Probing the formation of monoalkyl carbonates and pyrocarbonates in water with electrospray ionization mass spectrometry

The anionic hemiesters of carbonic acid with aliphatic alcohols were demonstrated to be formed in aqueous medium containing HCO3− or CO32− by using electrospray ionization mass spectrometry (ESI-MS). Some monoalkyl carbonates (MACs) have been previously detected by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D), but ESI-MS is structurally diagnostic and more sensitive allowing unequivocal characterization, which allowed, for the first time, detection of hydrogen pyrocarbonate and monoalkyl pyrocarbonates (MAPs). Methanol, ethanol, and different isomers of alcohols from C3 to C6 were studied. The relatively slow kinetics of formation of the MACs allowed us to confirm their formation in solution before the electrospray process takes place. The loss of CO2 to form the corresponding alkoxide is the most important process in gas phase dissociation, but dehydro-alkoxides were also observed. Monocyclohexyl and monocyclopentyl carbonates were also characterized by ESI-MS. These species, formed from cyclohexanol and cyclopentanol in diluted aqueous solution of HCO3−, are important because these alcohols are prototypes for the hydroxyl-containing portion of sterols. No biological role has been yet attributed to either MACs or MAPs, but their spontaneous formation in aqueous solution at room temperature indicates that these species are present in biological media.

Synthesis and Characterization of Tin (IV) Tungstate Nanoparticles – A Solid Acid Catalyst

Tin (IV) tungstate, a tetravalent metal acid salt was synthesized in the nanoform by chemical coprecipitation method using EDTA as capping agent. The material was found to be stable in mineral acids, bases and organic solvents except in HF and aquaregia. The material was characterized using EDS, TG/DTA, FTIR, XRD, SEM, HRTEM and BET surface area measurement. The molecular formula of the compound is 2SnO2 3WO3.5H2O determined from elemental analysis using TG/DTA. Surface morphology and particle size were obtained using SEM and HRTEM. The surface area was found to be 205-225m2/g. The Na+ exchange capacity found to be 3.8 meq/g, indicates the presence of surface hydroxyl group and hence the presence of Bronsted acid sites. The catalytic activity of the material was tested by using esterification and oxidation as model reactions. For the esterification of different alcohols, the percentage yield was found to be high for n-alcohol compared to isomeric alcohols. Oxidation of benzyl alcohol gives benzaldehyde and benzoic acid as the only products. © 2012 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Ion Pair Dynamics: Solvolyses of Chiral 1,3-Diarylallyl Carboxylates as a Case Study

Chiral ion pairs play a key role in modern enantioselective synthesis, though little is known about their properties. We have now used the special features of unsymmetrically substituted allyl derivatives to obtain unprecedented insight into ion pair dynamics. By employing chiral high-performance liquid chromatography, it was possible to follow the time-dependent concentrations of all four isomeric esters (two regioisomeric pairs of enantiomers) and all four isomeric alcohols generated during the hydrolysis of enantiopure 1-(4-chlorophenyl)-3-phenylallyl and 3-(4-chlorophenyl)-1-phenylallyl 4-nitrobenzoates. Combination of these results with the directly measured rate constant for the reaction of the laser-flash photolytically generated 1-(4-chlorophenyl)-3-phenylallyl cation with water provided a complete mechanistic scheme for allyl carboxylate solvolysis. It is demonstrated that solvolysis and internal return can be explained by the same intermediates. The correlation equation logk = s(N)(N + E) was used to elucidate the variable importance of external and internal return in the solvolysis reactions. This information will be crucial for the interpretation of the ultrafast dynamics of ion pairs generated by femtosecond laser pulses.

ChemInform Abstract: Regio‐ and Stereoselective Multicomponent Coupling Reaction of Alkynes and Dimethylzinc Involving Allylnickelacycles.

AbstractThe process affords mixtures of E/Z‐isomeric alcohols or (E)‐configurated dicarboxylic esters.

Immobilization of pyridinium nitrate and its application for the catalytic converting of β-pinene oxide

In this paper, differences among the catalytic effects of individual ammonium nitrates and influences of the catalysts used either in homogeneous and, moreover, pyridinium nitrate in heterogeneous forms of the catalytic converting of β-pinene oxide to perillic alcohol were studied. A special attention was paid to the heterogeneously catalyzed reaction where the representative of the used catalysts, pyridinium nitrate, was immobilized on various supports—mesoporous molecular sieves (MCM-41, SBA-15), silica and smectites (hectorite, montmorillonite K-10 and bentonite). Based on the obtained results, the individual influences on the course of the catalytic splitting, namely the properties and modifications of supporting materials were discussed. The best results using the catalyst immobilized on hectorite were achieved. The maximum relative concentration was 64 % for perillic alcohol and 17 % for perillic alcohol isomers 17 %.

Resonant infrared matrix-assisted pulsed laser evaporation of TiO2 nanoparticle films

The successful development of flexible, high performance thin films that are competitive with silicon-based technology will likely require fabricating films of hybrid materials that incorporate nanomaterials, glasses, ceramics, polymers, and thin films. Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is an ideal method for depositing organic materials and nanoparticles with minimal photochemical or photothermal damage to the deposited material. Furthermore, there are many nonhazardous solvents containing chemical functional groups with infrared absorption bands that are accessible using IR lasers. We report here results of recent work in which RIR-MAPLE has been employed successfully to deposit thin films of TiO2 nanoparticles on Si substrates. Using an Er:YAG laser (λ=2.94 μm), we investigated a variety of MAPLE matrices containing –OH moieties, including water and all four isomers of butyl alcohol. The alcohol isomers are shown to provide effective and relatively nontoxic solvents for use in the RIR-MAPLE process. In addition, we examine the effects of varying concentration and laser fluence on film roughness and surface coverage.

Discrimination of isomers and isobars by varying the reduced-field across drift tube in proton-transfer-reaction mass spectrometry (PTR-MS)

Proton-transfer-reaction mass spectrometry (PTR-MS) is a powerful technique for the real time trace gas analysis of volatile organic compounds (VOCs). However, quadrupole mass spectrometer (MS) used in PTR-MS has a relatively low mass resolution and is therefore not suitable for differentiating isobars. Furthermore, because of the lack of chemical separation before analysis, isomers can not be identified, either. In the present study, by varying the reduced-field E/N in the reaction chamber with a range of 50–180 Td in PTR-MS, we studied the product ion distribution (PID) of three sets of isobars/isomers, i.e. n-propanol/iso-propanol/acetic acid, propanal/acetone and four structural isomers of butyl alcohol. The profiles of the reduced-field dependence (PFD) of the PID under the chosen E/N-values show obvious differences which can be used to discriminate between these isobars/isomers thus enabling the titled method. Noticeably, we have observed that even the isomers, in the case of four structural isomers of butyl alcohol, which show little difference with each other at high reduced-field, can be discriminated easily at low reduced-field. Finally, two examples for the application of this method are discussed: (1) cyclohexanone was identified to be a major compound in the headspace of medical infusion sets; and (2) the differentiation and quantification of propanal and acetone in three synthetic mixtures with different ratios. This study presents a potential method to distinguish and quantify isobars/isomers conveniently in practical applications of PTR-MS analysis without additional instrumental configurations.

First isolation of disubstituted cis-5,6-dihydro-1,10-phenanthrolines. lipase-mediated resolution of cis- and trans-phenoxy alcohol isomers and assignment of absolute stereochemistry via cd and nmr spectroscopy

5,6-Dihydro-1,10-phenanthrolines can display axial and central chirality. In conjunction with the ligating properties of the diimino moiety, this class of compounds is of great interest to applications in supramolecular chemistry. We report the first preparation of cis-5,6-dihydro-1,10-phenanthroline derivatives by reacting triphenyl borate with the corresponding epoxide precursor. We found that solvent and temperature choice determined the stereoselectivity of the epoxide opening giving rise to the cis (14:1 dr) or trans (99:1 dr) product. Racemates of each stereoisomeric mixture, cis- and trans-phenoxy alcohol, were separated via highly enantioselective transesterifications with lipase PSCI from Burkholderia cepacia (97% ee, E > 200). Stereochemical assignments were carried out using CD and X-ray analyses in conjunction with NMR studies of α-methoxy-α-(trifluoromethyl)phenylacetic acid and α-methoxyphenylacetic acid esters.

Regioselective Base-Free Intermolecular Aminohydroxylations of Hindered and Functionalized Alkenes

Regioselective base-free intermolecular aminohydroxylations of functionalized trisubstituted and 1,1-disubstituted alkenes employing benzoyloxycarbamate 3a and catalytic OsO(4) are described. In all cases, the more substituted alcohol isomer is favored. Sluggish reactions could be promoted by gentle heating, the use of amine ligands, or increased catalyst loadings. A competitive rearrangement was observed with a secondary allylic alcohol substrate. The adducts serve as useful precursors to dehydroamino acids.

Docking study on Mycobacterium tuberculosis receptors AccD5 and PKS18 with selected phytochemicals

Epidemiological studies have indicated that 1.7 billion people, as much as one third of the world's population, are infected with Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB). This pathogen is responsible for more human deaths than any other single infectious agent throughout the centuries of human history. Considering the world-wide TB problems, there is an urgent need to develop relatively inexpensive new drugs to treat this deadly disease. Natural products isolated from plants have played an important role in discovery of drugs against infectious diseases. In the present study, three ligand molecules (basically secondary metabolites) which were commonly present in the plants were docked with the selected Mycobacterium receptor AccD5 and PKS18. Among them Phytol had a significant inhibitory activity with the receptor AccD5 binding to the pocket (GLY 241- GLY 242) forming hydrogen bonds at a very low energy value, thus forming a stable complex.The active compounds were found to be diterpene alcohol and isomers of diterpene alcohol. These molecules had a good number of conformations showing the flexible behavior of the ligand. The total energy of the receptor and ligand complexes has also been calculated.

Thermodynamic and surface characterisation of (S)-5-dodecycloxy-2-[[[4-(2-methylbutoxy) phenyl]imino]metheyl]phenol thermotropic liquid crystal by inverse gas chromatography

The inverse gas chromatography method was used to obtain thermodynamic and surface properties of the calamitic thermotropic liquid crystalline material, (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol, which is a Schiff base. The retention diagrams of the infinitely diluted solutions of acetate and alcohol isomers of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol were plotted between 313 and 383 K using the inverse gas chromatography method. The isomer seperation of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol isomers as chromatographic probes was represented by retention diagrams. The thermodynamic interaction parameters such as the Flory–Huggins liquid crystal–solvent parameter and the hard-core liquid crystal–solvent parameter, the weight fraction activity coefficient and the exchange parameters such as the effective energy, enthalpy and entropy were determined for the studied solvents at infinite dilution. Then the partial molar heat of sorption, the partial molar heat of mixing at infinite dilution and as well as the molar heat of vaporisation of the studied solvents were determined in the isotropic phase of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol. To characterise the surface properties of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol, retention diagrams of several non-polar and polar solvents with (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol were measured in the temperature range from 313 to 333 K by inverse gas chromatography. The surface energy, the thermodynamic adsorption parameters and the acid–base constants of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol in the crystalline phase were determined.