Lamellar zirconium phosphonates containing pendant sulphonic acid groups

The versatile sulphonic acid group has been introduced into the family of interlamellar anchored materials. Zirconium bis-3-sulphopropylphosphonate is an example of an aliphatic acid. Zirconium bis-2-(sulphophenyl)ethylphosphonate is an example with an aromatic sulphonic acid group. In general, the sulphonic acids are not as crystalline as the carboxylic acid analogs. This is probably due to the relatively large size of the sulphonic acid group compared to the available cross sectional area of the layer face. The aliphatic compounds are more crystalline than the aromatics, as is expected from size considerations. The sulphonic acid group in both crystalline and semi-crystalline examples is accessible to reaction with bases. A few preliminary experiments have demonstrated the utility of these compounds as both strong acid ion exchangers and Bronsted acid catalysts. The layered sulphonic acid—zirconium 3-sulphopropylphosphonate—is thermally stable to well over 200°C. This indicates good potential for applications in Bronsted catalysis. This stability compares favorably with organic resin based sulphonic acids.The sulphonic acid class of interlamellar anchored materials have now been established. Both aliphatic and aromatic examples have been prepared. The utility of the sulphonic acids has been demonstrated with the typical reactions of this functional group. Specifically, the acids have been shown to be strong acid cation exchangers and a Bronsted acid catalyst. In addition, we have begun to develop an insight into the structural ramifications of these compounds. The size constraints of the zirconium phosphate type backbone are evident. Further, the thermal stability of this group of compounds is encouraging relative to its applications potential.     

Enantioselective synthesis of (S)- and (R)-α-methylserines: application to the synthesis of (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinals

This report describes the synthesis of enantiomerically pure (S)- and (R)-α-methylserines on a multigram scale, starting from the Weinreb amide of 2-methyl-2-propenoic acid and using a stereodivergent synthetic route that involves a Sharpless asymmetric dihydroxylation reaction. As a synthetic application of these quaternary α-amino acids, they were used as starting materials in the synthesis of the well-known valuable homochiral (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinal building blocks.     

A simple, novel and convenient method for the synthesis of 1-aminophosphinic acids: synthesis of a novel C2-symmetric phosphinic acid pseudodipeptide

A simple, efficient and novel method has been developed for the synthesis of 1-aminophosphinic acids from simple starting materials. Treatment of aromatic aldehydes with ammonia and hypophosphorus acid gives novel C₂-symmetric 1-aminoarylmethylphosphinic acids. The synthesis of novel C₂-symmetric phosphinic acid pseudodipeptides is also discussed.     

Acyl/aroyl Meldrum’s acid as an enol surrogate for the direct organocatalytic synthesis of α,β-unsaturated ketones

The operationally simple, robust and straightforward organocatalytic protocol is developed for the synthesis of E-selective α,β-unsaturated ketones. The method utilizes simple and easily accessible starting materials such as Meldrum’s acid, carboxylic acid, aldehyde and simple bifunctional amine catalyst. The tandem organocatalytic process utilizes acyl/aroyl Meldrum’s acid as an enol surrogate for the effective Doebner-Knoevenagel type condensation reactions. A wide variety of aldehydes, carboxylic acids and base sensitive functional groups are well tolerated under the mild reaction conditions.     

Oxidative ring opening of 3-hydroxyquinoline-2,4(1H,3H)-diones into N-(α-ketoacyl)anthranilic acids

N-(α-Ketoacyl)anthranilic acids were prepared by oxidative ring opening of 3-hydroxyquinoline-2,4(1H,3H)-diones by using paraperiodic acid (H₅IO₆) or sodium periodate (NaIO₄). The optimisation of the reaction conditions is described as well as the utilisation of N-(α-ketoacyl)anthranilic acids in the preparation of anthranilic acid hydrochlorides.     

Efficient kinetic resolution of amino acids catalyzed by lipase AS ‘Amano’ via cleavage of an amide bond

Herein the efficient kinetic resolution of non-natural alpha-amino acids catalyzed by lipase AS ‘Amano’ via cleaving the amide bond is reported. The starting materials were the corresponding amino acid amides and the amino acids were generated with ees of up to 99% with E values of >600. These results indicated that the lipase AS ‘Amano’ could be a powerful amide hydrolase for the kinetic resolution of amino acid starting from the corresponding amino acid amides.     

Some new protocols for the assignment of absolute configuration by NMR spectroscopy using chiral solvating agents and CDAs

The utility of enantiopure BINOL (1,10-Bi-2-naphthol), in a ternary ion-pair complex, which is obtained using a carboxylic acid and an organic base, as a versatile chiral solvating agent (CSA) has been demonstrated for chiral analysis and the absolute configuration assignment of hydroxy acids. Another protocol where the utility of NOBIN as a CSA has been developed for discrimination and absolute configuration assignment of acids, hydroxy acids and their derivatives with a distinct strategy where a third ingredient, p-toluenesulfonic acid (p-TsOH) serves as a linker. In addition some three component chiral derivatization protocols have been introduced, such as the use of 2-formylphenylboronic acid and enantiopure mandelic acid or a primary amine for the determination of the configuration of primary amines and hydroxy acids, respectively. A simple, rapid and highly efficient three component chiral derivatizing protocol has also been discussed which was developed for assigning the absolute configuration of chiral α-hydroxy acids and their derivatives, which involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and (S)-[1,1-binaphthalene]-2,2-diamine separately. In a few examples, the DFT based theoretical calculations have been carried out to determine the geometry optimized structures of the complexes.     

Identification and determination of carboxylic acids in food samples using 2-(2-(anthracen-10-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)ethyl 4-methylbenzenesulfonate (APIETS) as labeling reagent by HPLC with FLD and APCI/MS

A new labeling reagent for carboxylic acids, 2-(2-(anthracen-10-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)ethyl 4-methylbenzenesulfonate (APIETS) has been designed and synthesized. It was used to label eight fatty acids (lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid and linolenic acid) and four hydroxy pentacyclic triterpene acids (oleanolic acid, ursolic acid, betulinic acid and maslinic acid), successfully. APIETS could easily and quickly label carboxylic acids in the presence of K₂CO₃ catalyst at 85 °C for 35 min in N,N-dimethylformamide solvent. The carboxylic acids derivatives were separated on a C₈ reversed-phase column with gradient elution and fluorescence detection at λ_ex/λ_em = 315/435 nm. Identification of these derivatives was carried out by online mass spectrometry with atmospheric pressure chemical ionization in positive ion mode. The detection limits obtained were 13.37-30.26 fmol (signal-to-noise ratio of 3). The proposed method has been applied to the quantification of carboxylic acids in sultana raisin (Thompson seedless), hawthorn flake (Crataegus pinnatifida Bge.), Lycium barbarum seed oil and Microula sikkimensis seed oil with recoveries over 95.3%. It has been demonstrated that APIETS is a prominent labeling reagent for determining carboxylic acids with high performance liquid chromatography.     

A versatile method for the synthesis of substituted 1-aminohydantoin derivatives

An efficient and versatile method has been developed for the synthesis of 1-aminohydantoin derivatives which can be substituted at all the possible positions of the hydantoin ring. The starting materials are aldehydes, ketones, carboxylic acids and hydrazides as well as isocyanates readily available from commercial sources. The semicarbazide-type reaction product of an N-acyl-N′-(1-cyanoalkyl)hydrazine, obtained from the above materials by methods known from the literature, and an isocyanate is cyclized in the presence of a basic catalyst to yield 1-acylamino-4-imino-2-oxoimidazolidine derivatives whose acid catalyzed hydrolysis leads to 1-aminohydantoin derivatives in good to excellent yields. The last two steps are carried out in a single reaction medium.     

Templated scaffolds of cis- and trans-tetrahydrofuran γ-amino acids: γ-azido-β-hydroxy-tetrahydrofuran-2-carboxylates from pentono-δ-lactones

Short syntheses of enantiomeric templated scaffolds of cis- and trans-tetrahydrofuran γ-amino acids from pentono-δ-lactones derived from arabinose and ribose are reported; an unexpectedly efficient synthesis of a templated tetrahydrofuran β-amino acid by azide displacement of a triflate β to an ester function proceeds with remarkably little elimination. These materials should allow evaluation of such peptidomimetics to induce predisposition towards secondary structures.     

Trichosporon beigelli esterase (TBE): a versatile esterase for the resolution of economically important racemates

A hydrolase producing strain Trichosporon beigelli esterase (TBE) isolated from local cottage cheese in its native form has displayed versatility and high efficacy in the kinetic resolution of a wide range of economically important substrates, which include racemic secondary alcohols, such as 1-(6-methoxy-2-naphthyl)ethanol (E ∼ 316), 1-(3,4-methylenedioxyphenyl)ethanol and pentanol (E ∼ 180 and 156 resp.), and alkyl esters of carboxylic acids such as ibuprofen (E ∼ 340), 2-(benzylthio)propanoic acid (E ∼ 1000). In other substrates such as in the primary alcohol 2-(6-methoxy-2-naphthyl)propan-1-ol and carboxylic acids such as 2-(5-bromo-6-methoxy-2-naphthyl)propanoic acid, 2-(2-naphthyloxy)propanoic acid, and substituted 2-thiopropanoic acids, it displayed moderate to low selectivity. Commercial lipases such as CCL, PPL, and PSL were also used in the resolution of the substrates for comparative studies.     

Microbial synthesis and characterization of polyhydroxyalkanoates with fluorinated phenoxy side groups from Pseudomonas putida

Microbial poly(3-hydroxyalkanoates) (PHAs) with fluorinated phenoxy side groups were produced by Pseudomonas putida when fluorophenoxyalkanoic acids were used as carbon sources. 11-(2-Fluorophenoxy)undecanoic acid (2FPUDA), 11-(3-fluorophenoxy)undecanoic acid (3FPUDA), 11-(4-fluorophenoxy)undecanoic acid (4FPUDA), 11-(2,4-difluorophenoxy)undecanoic acid (2,4DFPUDA), 11-(2,4,6-trifluorophenoxy)undecanoic acid (2,4,6TFPUDA), and 11-(2,3,4,5,6-pentaflurophenoxy)undecanoic acid (2,3,4,5,6PFPUDA) were used as carbon sources in the present study. When cells were grown with 2,4DFPUDA, the production of homo poly(3-hydroxy-5-(2,4-difluorophenoxy)pentanoate) was confirmed by NMR and GC/MS analyses. Fluorine atoms inserted into the side chain of the PHA dramatically affected its physical properties. In marked contrast to medium chain length (MCL) PHA, this fluorinated PHA was opaque, cream colored, and possessed greater crystallinity and a higher melting point (∼100 °C) than did the other MCL PHAs. Surface contact angle evaluation revealed that the PHA with two fluorine atoms possessed water-shedding properties. The number of substituted fluorine atoms in the carbon source affected cell growth and difluorine-substituted phenoxyalkanoic acids reduced cell growth, and polymer production compared to non-substituted phenoxyalkanoic acids. No polymeric materials were obtained using either 2,4,6TFPUDA or 2,3,4,5,6PFPUDA.     

Electrogenerated-bases promoted electrochemical synthesis of N-bromoamino acids from imines and carbon dioxide

In this paper, the one-step synthesis of N-bromoamino acids has been developed by electrolyzing imines and carbon dioxide (4 MPa). The electrosynthesis was performed in an undivided cell with Ni cathode and Al sacrificial anode containing n-Bu₄NBr–DMF as supporting electrolyte with a constant current at room temperature. The N-bromoamino acids were afforded in moderate to good yields rather than traditional α-amino acids. To explore the truth, some influenced factors (cathode materials, supporting electrolyte, and electricity etc.) were investigated. The experimental results indicated that the NH group of the α-amino acid could be deprotonated by alkyl anion R⁻ (carbanion, a strong base), followed by the oxidation of hypobromous acid resulted from the two-step oxidation of the bromide ion at the anode, and produced the N-bromoamino acid. Finally, the reaction mechanism was briefly discussed.     

Solid-phase extraction of organic compounds in atmospheric aerosol particles collected with the particle-into-liquid sampler and analysis by liquid chromatography-mass spectrometry

Atmospheric aerosol particles, collected with the particle-into-liquid sampler at SMEARII station in Finland in mid-August 2007, were analysed for biogenic acids. The sample pretreatment method, comprising solid-phase extraction with anion exchange and hydrophilic-lipophilic balance materials, was optimized. Extraction efficiencies of solid-phase extraction from 10 and 20 ml samples were about 100%, with average relative standard deviation of 8.9%, in concentration range from 12.5 to 50 ng/ml of the acid. Extraction of aldehydes was less successful, with efficiencies from 69 to 163% and average 10% deviation. Pretreated samples were analysed by reversed phase high performance liquid chromatography with ion trap mass spectrometric detection. Limits of detection achieved for organic acids with the analytical procedure developed ranged from 9 to 27 μg/l of extracted sample, while limits of quantitation were from 31 to 90 μg/l. Oxidation with ozone was used for the preparation of the acid of β-caryophyllene (β-caryophyllinic acid), which was also studied in aerosol samples. MS² experiments were used to confirm the identification of trans-pinic, trans-pinonic and β-caryophyllinic acids. Azelaic, hexadecanoic, cis-pinonic, and cis- and trans-pinic acids were quantitated in the samples with use of authentic standards, while the concentrations of trans-pinonic and β-caryophyllinic acids were determined with cis-pinonic acid as surrogate. Also, the contribution of β-caryophyllene oxidation products to aerosol organic carbon was evaluated. Aldehydes could not be analysed in real samples due to the insufficient extraction. The particle-into-liquid sampler proved to be suitable for the collection of aerosol particles for the elucidation of daily and diurnal variation of selected species. The optimized sample pretreatment, together with the analysis method, offer a promising approach for the study of aerosol chemical composition, where artifact formation is minimal and time resolution is good.     

Two diasteoisomers of 5-hydroxy-6-methylpipecolic acid from seeds of Fagus silvatica L.

Two diastereoisomers of 5-hydroxy-6-methylpipecolic acid have been isolated from beechnuts. The configurations of the two amino acids have been assigned as (2S, 5S, 6S) (1) and (2S, 5R, 6S) (2). The determination of structure and configuration for the two new amino acids is mainly based on spectroscopic and rotatory evidence. The ¹³C-NMR and ¹H-NMR spectra of the three ionic forms of the two amino acids and of S-pipecolic acid and (2S, 5R)-5-hydroxypipecolic acid and the CD-curves of the cations and amfoions of 1, 2, and (2S, 5R)-5-hydroxypipecolic acid have been recorded.     

Easy access to orthogonally protected α-alkyl aspartic acid and α-alkyl asparagine derivatives by controlled opening of β-lactams

The controlled opening of the N1C2 bond in 1-carbamate-substituted 2-azetidinones derived from amino acids by O- and N-nucleophiles provided a straightforward access to orthogonally protected α-alkyl aspartic acid and asparagine derivatives. The use of DBU or sodium azide as additive is essential for expedient cleavage by amino acids to the corresponding β-aspartic acid dipeptides.     

The Identification of New Triterpenoids in Eucalyptus globulus Wood

Eight polyhydroxy triterpenoid acids, hederagenin, (4α)-23-hydroxybetulinic acid, maslinic acid, corosolic acid, arjunolic acid, asiatic acid, caulophyllogenin, and madecassic acid, with 2, 3, and 4 hydroxyl substituents, were identified and quantified in the dichloromethane extract of Eucalyptus globulus wood by comparing their GC-retention time and mass spectra with standards. Two other triterpenoid acids were tentatively identified by analyzing their mass spectra, as (2α)-2-hydroxybetulinic acid and (2α,4α)-2,23-dihydroxybetulinic acid, with 2 and 3 hydroxyl substituents. Two MS detectors were used, a quadrupole ion trap (QIT) and a quadrupole mass filter (QMF). The EI fragmentation pattern of the trimethylsilylated polyhydroxy structures of these triterpenoid acids is characterized by the sequential loss of the trimethylsilylated hydroxyl groups, most of them by the retro-Diels-Alder (rDA) opening of the C ring with a π-bond at C12-C13. The rDA C-ring opening produces ions at m/z 320 (or 318) and m/z 278 (or 277, 276, 366). Sequential losses of the hydroxyl groups produce ions with m/z from [M - 90] to [M - 90*y], where y is the number of hydroxyl substituents present (from 2 to 4). Moreover, specific cleavage in ring E was observed, passing from m/z 203 to m/z 133 and conducting other major fragments such as m/z 189.     

<em>In Vitro</em> Anti-diabetic Activities and Chemical Analysis of Polypeptide-k and Oil Isolated from Seeds of <em>Momordica charantia</em> (Bitter Gourd)

The amino acid and fatty acid composition of polypeptide k and oil isolated from the seeds of Momordica charantia was analysed. The analysis revealed polypeptide k contained 9 out of 11 essential amino acids, among a total of 18 types of amino acids. Glutamic acid, aspartic acid, arginine and glycine were the most abundant (17.08%, 9.71%, 9.50% and 8.90% of total amino acids, respectively). Fatty acid analysis showed unusually high amounts of C18-0 (stearic acid, 62.31% of total fatty acid). C18-1 (oleic acid) and C18-2 (linoleic acid) were the other major fatty acid detected (12.53% and 10.40%, respectively). The oil was devoid of the short fatty acids (C4-0 to C8-0). Polypeptide k and oil were also subjected to in vitro α-glucosidase and α-amylase inhibition assays. Both polypeptide k and seed oil showed potent inhibition of α-glucosidase enzyme (79.18% and 53.55% inhibition, respectively). α-Amylase was inhibited by 35.58% and 38.02%, respectively. Collectively, the in vitro assay strongly suggests that both polypeptide k and seed oil from Momordica charantia are potent potential hypoglycemic agents.     

Occurrence of Cis-11,12-Methylene-Hexadecanoic Acid in the Red Alga Solieria pacifica (Yamada) Yoshida

Fatty acids in marine algae have attracted the attention of natural chemists because of their biological activity. The fatty acid compositions of the Solieriaceae families (Rhodophyceae, Gaigartinales) provide interesting information that unusual cyclic fatty acids have been occasionally found. A survey was conducted to profile the characteristic fatty acid composition of the red alga Solieria pacifica (Yamada) Yoshida using gas chromatography-mass spectrometry (GC-MS), infrared spectroscopy (IR), and proton nuclear magnetic resonance spectroscopy (¹H-NMR). In S. pacifica, two cyclopentyl fatty acids, 11-cyclopentylundecanoic acid (7.0%), and 13-cyclopentyltridecanoic acid (4.9%), and a cyclopropane fatty acid, cis-11,12-methylene-hexadecanoic acid (7.9%) contributed significantly to the overall fatty acid profile. In particular, this cyclopropane fatty acid has been primarily found in bacteria, rumen microorganisms or foods of animal origin, and has not previously been found in any other algae. In addition, this alga contains a significant amount of the monoenoic acid cis-11-hexadecenoic acid (9.0%). Therefore, cis-11,12-methylene-hexadecanoic acid in S. pacifica was likely produced by methylene addition to cis-11-hexadecenoic acid.     

Reduction of nitroblue tetrazolium to formazan by folic acid

The reduction of nitroblue tetrazolium (NBT) to formazan by folic acid, N-(4-aminobenzoyl) glutamic acid, and other amino acids was studied in this paper. The reduction involves only one of the two tetrazolium rings of NBT. The reaction is considerably more rapid with folic acid and N-(4-aminobenzoyl) glutamic acid than with the other amino acids under study. The electron donor moiety appears to be the carboxylic acid in the alpha position. N-ethyl-N′(3-dimethylaminopropyl) carbodiimide notably increases the rate of the reaction and promotes the reduction of both tetrazolium rings.