Diterpenoids ofPulicaria salviifolia. III. The structure of salvicinin

The new diterpene acid salvicinin has been isolated from the epigeal part ofPulicaria salviifolia and its structure has been established as 15-acetoxy-6α-hydroxy-trans-cleroda-3,13-dien-19-oic acid. A capacity of salvicinin for undergoing lactonization in the presence of acetic anhydride has been revealed, and the lactone formed has been isolated and chracterized.     

Isolation, synthesis and photochemical properties of almazolone, a new indole alkaloid from a red alga of Senegal

An indole alkaloid bearing an oxazolone ring, christened almazolone, has been isolated from a new collection of Haraldiophyllum sp. from Dakar (Senegal), as an 88:12 mixture of (Z)/(E) stereoisomers. The relative ratio could be modified under controlled photochemical and thermal processes. The product (Z)-3-indolyl-2-(phenyl-propionylamino)-acrylic acid obtained by oxazolone ring opening has also been observed. Its formation has been confirmed by alkaline hydrolysis of (Z)-almazolone available from synthesis, where condensation of indole-3-carboxaldehyde with (3-phenylpropionylamino)-acetic acid represents the key step.     

An example of quality control of fine chemical intermediates: related impurity analysis of industrial phthalic anhydride by reversed-phase high-performance liquid chromatography

A reliable reversed-phase high-performance liquid chromatographic method has been developed for analysis of related impurities in industrial phthalic anhydride (PA). Maleic acid (hydrolysis product of maleic anhydride), phthalimide, and benzoic acid were separated from phthalic acid (Pa, hydrolysis product of PA) on a C₁₈ column by gradient elution with acetonitrile and 0.1% (v/v) aqueous perchloric acid solution. This method is simple, sensitive, and accurate, and has been successfully applied to quality control of PA for industrial use.     

Eco-friendly synthesis of 2-aryl-1-arylmethyl-1H-benzimidazoles using alumina-sulfuric acid as a heterogeneous reusable catalyst

A cost-effective and eco-friendly synthesis of 2-aryl-1-arylmethyl-1H-benzimidazoles has been developed through the condensation of different aldehydes with o-phenylenediamine using alumina-sulfuric acid as a recyclable heterogeneous solid acid catalyst. Morphological properties of the catalyst have been investigated. Effect of different solvents and comparison of alumina-sulfuric acid with different acid catalysts have also been studied. A plausible mechanistic pathway has been proposed on the basis of the isotope labelling experiments where catalytic behaviour of alumina-sulfuric acid has been explained.     

ISolement du groupe des terres rares de l'apatite par l'acide di-(2-ethyhexyl)phosphorique (hdehp)

The liquid-liquid extraction of rare-earth elements (REE) by 0.75 M di-(2-ethylhexyl) phosphoric acid (HDEHP) in cyclohexane from perchloric acid (1–12M) has been investigated. At moderate perchloric acid molarities (1–6 M), the distribution coefficient, E, has an inverse third-power dependency upon the acid concentration in the aqueous phase. However, at higher perchloric acid concentrations, the slope of the resulting curve is about +18, which means a change in the extraction mechanism. In 12 M perchloric acid medium, REE are quantitatively and selectively extracted from apatite minerals, in the organic phase. In order to strip out all the lanthanides, back-extractions were carried out with 9 M hydrochloric acid solutions.     

Nature of light-absorbing pigments from Brazilian lichens identified by Raman spectroscopy

Light-absorbing pigments from different chemical classes have been identified from the lichens Usnea sp. and Crocodia aurata using Raman spectroscopy supported by quantum mechanical DFT calculations. Raman spectra were obtained directly from the lichen tissues as well as from isolated extracts. Usnic acid, a chemomarker of Usnea spp has been reported together with a minor constituent, namely stictic acid, which has been unambiguously identified by ¹H and ¹³C NMR spectral analysis. The structures of calycin and pulvinic dilactone isolated from Crocodia aurata have been confirmed by single crystal X-ray diffraction. The ubiquitous carotenoids have been characterized by FT-Raman and dispersive Raman microimaging in tissues of Usnea sp. and C. aurata, respectively. The Raman map has revealed the presence of a mixture of carotenoids heterogeneously distributed in the upper layer of C. aurata. In this work we have demonstrated that Raman spectroscopy can be used to monitor aromatic and conjugated polyenic pigments in different layers of lichen tissues.     

Investigation of the pyrolysis behaviour of brown algae before and after pre-treatment using PY-GC/MS and TGA

The pyrolysis behaviour of a number of brown macroalgae (seaweeds) collected in the UK such as Laminaria hyperborea and Fucus vesticulosus, are compared with the tropical algae Macrocystis pyrifera. Macroalgae contain a significant amount of alkali earth metals, halogens and a range of trace heavy metals. Pre-treatment of the algae has been performed to remove mineral matter in both water and weak acid. The pyrolysis behaviour of the residues has been investigated and the effect of processing on ash content and mineral composition has been determined. The pyrolysis behaviour of the raw samples and the residues from processing has been studied using thermal gravimetric analysis (TGA) and pyrolysis-GC/MS (Py-GC/MS). Total mineral matter has been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) before and after pre-treatment. The Py-GC/MS pyrograms at 500 °C indicate the presence of a range of ketones, pentosans, nitrogen containing compounds and phenols. The residues from pre-treatment have different pyrolysis behaviours, particularly after acid treatment. The pre-treatment schemes investigated can remove a significant proportion of the mineral matter and halogens although they also selectively extract polymeric material. The residues have lower ash content and lower nitrogen content. Results for pre-treatment in water are consistent with the removal of mannitol, while results for pre-treatment in acid are consistent with the removal of fucoidan, mannitol and the partial removal of laminarin. Py-GC/MS of the residue from pre-treatment in acid produces a similar pyrogram to alginic acid in which furfural is a dominant product. There appears to be potential for the production of fuels and chemicals from brown algae by pyrolysis although the reduction of mineral matter and halogens by pre-treatment is advantageous.     

The absolute stereochemistry of cascarillic acid

((1S,2R)-2-Hexylcycloprop-1-yl)acetic acid has been synthesised from cis-1,2-dihydroxymethylcyclopropane and shown to be identical to cascarillic acid obtained from cascarilla essential oil.     

Sequential cross-metathesis/cyclopropanation: short syntheses of (+/−)-cascarillic acid and (+/−)-grenadamide

The total synthesis of (+/−)-cascarillic acid has been achieved by a sequential cross-metathesis/Simmons-Smith cyclopropanation between, respectively, 1-octene with an appropriate unsaturated carboxylic acid. In parallel, a direct access to grenadamide was developed from 1-nonene with a readily available unsaturated amide. In both cases, the chemical yields were high (up to 98%) and the E/Z ratio was near 80/20. The synthesis of a dibromocyclopropane analogue has also been considered.     

Stereoselective synthesis of malyngic acid and fulgidic acid

A new stereoselective total synthesis of malyngic acid has been achieved from a known oxazolidinone derivative via eight steps involving the Evans asymmetric alkylation as the chirality-inducing step and chelation-controlled Zn(BH₄)₂ reduction of an α-hydroxy ketone intermediate for the installation of the 12,13-anti stereochemistry. Fulgidic acid, the C12-epimer of malyngic acid, has also been synthesized in eight steps from the same starting material by using syn-selective K-Selectride reduction of an α-alkoxy ketone intermediate.     

Chemistry of thorium : Volumetric determination of thorium

Thorium has been determined volumetrically. It has been precipitated with m-nitrobenzoic acid according to the method of Neish. Thorium m-nitrobenzoate has been then dissolved in sulphuric acid and titrated with titanous chloride to determine the NO₂-group which gives the amount of thorium directly.     

Short and efficient synthesis of (+)-subersic acids

An efficient synthesis of (+)-subersic acid, the unnatural enantiomer, has been achieved from sclareol and p-hydroxybenzoic acid.     

Soil bacterial hydrolysis leading to genuine aglycone—VIII : Structures of a genuine sapogenol protobassic acid and a prosapogenol of seed kernels of Madhuca longifolia L.

By virtue of the soil bacterial hydrolysis method, a genuine sapogenol named protobassic acid was obtained from the saponins of seed kernels of Madhuca longifolia L. (Sapotaceae), and the structure has been established as 2β, 3β, 6β, 23-tetrahydroxy-olean-12-en-28-oic acid (2a). In addition, the structure of a prosapogenol designated as Mi-glycoside I, which was isolated concurrently during the above microbiological procedure, has been elucidated as 3-0-β-d-glucopyranosyl-protobassic acid (3a). It has been suggested that protobassic acid (2a) may be a common sapogenol of several sapotaceous plants in place of hitherto approved bassic acid (1a).     

A convenient formal synthesis of (2S,3S)-3-hydroxy pipecolic acid

A convenient synthesis of (2S,3S)-3-hydroxy pipecolic acid starting from inexpensive and easily available l-(+)-tartaric acid has been described.     

Tri-n-octylphosphine sulfide: : A selective organic extractant

Tri-n-octylphosphine sulfide (TOPS) has been investigated as the stationary phase in reversed-phase partition paper Chromatographie separations using nitric or hydrochloric acids as the mobile phase. TOPS has also been studied as an extractant for metal ions. Silver, mercury (II), and palladium (II) were found to have RF values of zero when nitric acid was used as the mobile phase. These same ions were also selectively extracted from aqueous nitric acid solutions. Gold(III), mercury(II), palladium (II), and platinum (IV) were found to have RF values of zero when hydrochloric acid was used as the mobile phase. However, only gold(III) and mercury(II) were extracted from aqueous hydrochloric acid solutions in liquid-liquid extraction systems. Several separations were successfully performed from 1 M nitric acid.     

Synthesis of juniperonic acid

Synthesis of juniperonic acid [(all-Z)-5,11,14,17-eicosatetraenoic acid], has been achieved in eight steps and in 19% overall yield starting from eicosapentaenoic acid.     

Enantioselective synthesis of 1-deoxy-d-gulonojirimycin from a phenylglycinol-derived lactam

Cyclocondensation of (R)-phenylglycinol with appropriately γ-substituted δ-oxo acid derivatives provides bicyclic lactams from which the enantioselective synthesis of 1-deoxy-d-gulonojirimycin has been reported.     

Multicomponent reaction design: a one-pot route to substituted di-O-acylglyceric acid amides from α-diazoketones

A four-component assembly of substituted di-O-acylglyceric acid amides has been developed from α-diazoketones. The process involves copper-catalyzed reaction of the α-diazoketone with a carboxylic acid, and subsequent Passerini condensation of the in situ formed α-acyloxyketone.     

Synthesis of nucleoside aminooxy acids

First nucleoside aminooxy acids were synthesized from furanoid sugar phthalimidooxy acids by N-glycosylation with uracil, thymine, N-benzoylcytosine, 6-N-benzoyladenine and 2-N-acetyl-6-O-diphenylcarbamoylguanine. Boc or Fmoc protected uridine aminooxy acid derivatives have also been prepared. As oxyamine protecting group, the phthalimido group was shown to be instable in MeOH, leading to the imide ring-opening product in a reversible way. This reaction was accelerated under acid or basic conditions. A uridine dimer linked by N-oxy amide has also been prepared by coupling of uridine aminooxy ester with uridine phthalimidooxy acid. These nucleoside aminooxy acids might constitute useful building blocks for the development of novel RNA mimics and conjugates with other biomolecules or reporter compounds.     

GC/MS and 1H-NMR Analysis of Phytanic Acid Synthesized from Natural trans-Phytol and a Synthetic Phytol Standard

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a bioactive multi-branched fatty acid mainly synthesized by ruminants from trans-phytol which is found esterified in chlorophyll. Many clinical and biochemical studies were carried out with phytol and phytanic acid, but the stereochemistry of both compounds has not been detailed in either case. In this study, we released trans-phytol from a sample of fresh grass and isolated the natural product from the unsaponifiable matter by means of high-speed counter-current chromatography (HSCCC). The trans-phytol obtained by this measure was used as starting material for the synthesis of phytanic acid. The starting material and the products of this synthesis were compared to the compounds generated in parallel from commercial phytol labeled as “cis-/trans-mixture”. While the phytanic acid produced from trans-phytol from the grass sample was enantiopure on C-7 and C-11, the commercial phytol standard proved to be racemic. These differences could be elaborated by means of the trimethylsilylether of phytol and the methyl esters of phytanic acid. Likewise, ¹H-NMR of phytanic acid methyl ester was suitable to distinguish the natural 3R,7R,11R-/3S,7R,11R-diastereomers from all racemic 3RS,7RS,11RS-phytanic acid by means of the signal dispersion of the multiplets at ~2.1 and ~2.3 ppm. Our results indicate that racemic phytol has been used in different chemical, analytical and biochemical studies. Due to the extraordinary relevance of stereoisomerism, future studies should take advantage of the natural products, i.e. trans-phytol and phytanic acid, with R-configuration on C-7 and C-11. Moreover, the specific composition of the compounds used in studies should be addressed in future studies.