Artalbic acid, a sesquiterpene with an unusual skeleton from Artemisia alba (Asteraceae) from Sicily

From the aerial parts of Artemisia alba (Asteraceae) artalbic acid (1), a sesquiterpene with an unusual skeleton, was isolated. Its structure was elucidated on the basis of extensive proton, ¹³C and two-dimensional NMR experiments, as well as by transformation in its methyl ester derivative.     

π-d-Interaction and the temperature dependent magnetic circular dichroism spectra of low spin Fe(III)-heme compounds

The magnetic circular dichroism (MCD) of metmyoglobin cyanide, ferricytochromec and horseradish peroxidase cyanide were measured in the region 340–800 nm over a range of temperatures from 293 to 15 K. All three species show the temperature dependent MCD (TheC-type effects ∼1/T) in both visibleQ and near UVB bands. While the MCD and absorption inB- region as well as the absorption inQ region are quite similar for all three species the MCD inQ- bands reveal the marked differences, especially at low temperatures. To explain these observations, the theoretical treatment based on our previous model (A. P. Mineyev and Yu. A. Sharonov, 1978, Theoret. Chim. Acta (Berl.)49, 295–307) is proposed. The key point of this consideration is the configuration π-d- interaction which in addition to our previous analysis involves the first excited Fe(III)-ion Kramers doublet and theB-Q-mixing effects. The simultaneous least square fit of MCD and absorption data allows to evaluate the π —d- parameters which appear to be of the order of 10²−10³ cm⁻¹. The role of the π -d- interaction in the forming of hemoprotein spectra are discussed.     

(R)-(+)-[VCD(+)945]-4-Ethyl-4-methyloctane, the simplest chiral saturated hydrocarbon with a quaternary stereogenic center

Enantiopure (R)-(+)-[VCD(+)945]-4-ethyl-4-methyloctane, the simplest chiral saturated hydrocarbon with a quaternary stereogenic center, was synthesized by the use of MαNP acid method, and its absolute configuration was first unambiguously determined by the ¹H NMR anisotropy, X-ray crystallography, and VCD methods.     

Biocatalytic reduction system for the production of chiral methyl (R)/(S)-4-bromo-3-hydroxybutyrate

An effective method for producing methyl 4-bromo-3-hydroxybutyrate enantiomers was developed using an engineered protein. Escherichia coli transformant cells containing a mutant β-keto ester reductase (KER-L54Q) from Penicillium citrinum and a cofactor-regeneration enzyme such as glucose dehydrogenase (GDH) or Leifsonia sp. alcohol dehydrogenase (LSADH) were used to produce methyl (S)-4-bromo-3-hydroxybutyrate from methyl 4-bromo-3-oxobutyrate. On the other hand, the production of methyl (R)-4-bromo-3-hydroxybutyrate was achieved by asymmetric reduction of methyl 4-bromo-3-oxobutyrate with a mutant phenylacetaldehyde reductase (PAR-HAR1) from Rhodococcus sp. ST-10.     

Synthesis of polylactide using a zinc complex containing (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine

The reaction between ZnCl₂ and (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine (S-EPP) as a chiral ligand affords [ZnCl₂(S-EPP)], whose structure has been determined by X-ray crystallography. [ZnEt₂(S-EPP)] has demonstrated high activity toward the polymerization of rac-lactide with a maximum turnover frequency (TOF) of 121. Despite the intended stereocontrol by employing a chiral ligand, however, the observed heterotacticity was limited to under 0.6. The MWDs of the PLAs were found to be modulated by changing the solvent or controlling the concentration of the monomer in the solution. The glass transition temperature (T_g) was critically dependent on the MW within the narrow MWD regime, but the dependence became significantly shallow when the MWD was broadened.     

Synthesis of substituted benzimidazo[2,1-a]isoquinolines and its condensed analogues using Pd(0)-catalyzed cyclization/C-H activation

An efficient route for the synthesis of benzimidazo[2,1-a]isoquinolines and its condensed analogues has been developed via the palladium-catalyzed cyclization/C-H activation of N-allyl and N-methallyl derivatives of benzimidazoles.     

The use of a thermostable signature amidase in the resolution of the bicyclic synthon (rac)-γ-lactam

The resolution of the bicyclic synthon (rac)-γ-lactam (2-azabicyclo[2.2.1]hept-5-en-3-one) is an important step in the synthesis of a group of chemotherapuetic agents known as carbocyclic nucleosides. The archaeon Sulfolobus solfataricus MT4 produces a thermostable γ-lactamase that has a high sequence homology to the signature amidase family of enzymes. It shows similar inhibition patterns of amidases towards benzonitrile, phenylmethylsulfonyl fluoride and heavy metals such as Hg²⁺, and is activated by thiol reagents. The enzyme selectively cleaves the (+)-enantiomer from a racemic mix of γ-lactam. It also exhibits general amidase activity by cleaving linear and branched aliphatic and aromatic amides. The enzyme catalyses the synthesis of benzoic hydrazide from benzamide preferentially to benzamide cleavage in the presence of excess hydrazine. This enzyme has potential for use in industrial biotransformations in the production of both carbocyclic nucleosides and hydrazides.     

Stereoselective synthesis of methyl branched chiral deoxypropionate units: a new route for synthesis of insect pheromone (−)-lardolure and (2R,4R,6R,8R) 2,4,6,8-tetramethylundecanoic acid

(−)-Lardolure and (2R,4R,6R,8R)-2,4,6,8-tetramethylundecanoic acid have been synthesized via lipase catalyzed desymmetrization strategy to create two methyl chiral centers. Other key steps involved in the synthesis are Wittig reaction, Evan’s asymmetric alkylation, Grignard reaction, Pd-catalyzed isomerization of primary allylic alcohol to corresponding saturated aldehyde, and PhNO/proline catalyzed MacMillan α-hydroxylation.     

Study of the vibrational spectra of SO2, H2O and D2O using the U(4) algebraic model

Using the U(4) algebraic model, in this work we report a study of the vibrational spectra of SO₂, H₂0¹⁸ and D₂O¹⁶. The inclusion of intermode couplings in algebraic models has been stated to give a deep insight into detailed spectroscopy for these bent XY₂ molecules. Improved set of algebraic parameters has been reported to provide improved RMS deviations for these molecules.     

The reaction of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones with dinucleophilic reagents: a convenient route to fluoroalkylated nitrogen-containing tricyclic compounds

The reactions of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones (2) with hydrazine hydrate and phenyl hydrazine were investigated. The reaction of 2 with hydrazine hydrate in ethanol under reflux condition readily gave 2-fluoroalkyl-4H-pyrazolo[5,1-b]quinazolin-9-ones (3) in high yields. The reaction of 2 with phenyl hydrazine, however, resulted in the formation of 2-(2-phenyl-5-fluoroalkyl-2H-pyrazol-3-yl) benzoic acids (7). Further treatment of 7 with PPA gave 1-phenyl-4,9-dihydro-3-fluoroalkyl-1H-pyrozolo[3,4-b]quinolin-4-ones (4) in 65-80% overall yields.     

Antimony trichloride catalyzed three-component reaction of urea, aldehydes and cyclic enol ethers: a novel route to 4-arylhexahydrofuro[2,3-d]pyrimidin-2(3H)-ones

Antimony trichloride efficiently catalyses diastereoselective three-component reaction of urea, aromatic aldehydes and 2,3-dihydrofuran or 3,4-dihydro-2H-pyran leading to 4-arylhexahydrofuro[2,3-d]pyrimidin-2(3H)-ones and 4-arylhexahydro-1H-pyrano[2,3-d]pyrimidin-2(8aH)-ones, respectively in good yield.     

A new HPLC-DAD-MS/MS method for the simultaneous determination of major compounds in the crude extract of Lychnophora salicifolia Mart. (Brazilian arnicão) leaves: Application to chemical variability evaluation

Lychnophora salicifolia Mart., which occurs in the Brazilian Cerrado in the states of Bahia and Minas Gerais as well as in the southeast of the state of Goiás, is the most widely distributed and also the most polymorphic species of the genus. This plant is popularly known to have anti-inflammatory and analgesic activities. In this work, we have studied the variation in terms of polar metabolites of ninety-three Lychnophora salicifolia Mart. specimens collected from different regions of the Brazilian Cerrado. Identification of the constituents of this mixture was carried out by analysis of the UV spectra and MS data after chromatographic separation. Twenty substances were identified, including chlorogenic acid derivatives, a flavonoid C-glucoside, and other sesquiterpenes. The analytical method was validated, and the reliability and credibility of the results was ensured for the purposes of this study. The concentration range required for analysis of content variability within the analyzed group of specimens was covered with appropriate values of limits of detection and quantitation, as well as satisfactory precision and recovery. A quantitative variability was observed among specimens collected from the same location, but on average they were similar from a chemical viewpoint. In relation to the study involving specimens from different locations, there were both qualitative and quantitative differences among plants collected from different regions of Brazil. Statistical analysis revealed that there is a correlation between geographical localization and polar metabolites profile for specimens collected from different locations. This is evidence that the pattern of metabolites concentration depends on the geographical distribution of the specimens.     

Mild and practical stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts using Appel agents (PPh3/CBr4): a facile synthesis of semiplenamides C and E

Appel agents (PPh₃/CBr₄) have been utilized for high-yielding stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts at room temperature. The method has been applied for the synthesis of naturally occurring bioactive fatty acid amides, semiplenamides C and E.     

Polycyclic N-heterocyclic compounds. Part 61: A novel Truce-Smiles type rearrangement reaction of 4-(2-cyanovinyloxy)butanenitriles to give cycloalkeno[1,2-d]furo[2,3-b]pyridines

The cycloalkeno[1,2-d]furo[2,3-b]pyridine skeleton was conveniently synthesized from fused 4-(2-cyanovinyloxy)butanenitriles in one step through sequential intramolecular Michael addition, β-elimination and intramolecular nucleophilic addition. This sequence thus consists of a novel Truce-Smiles type rearrangement followed by cyclization. The 5-amino derivatives were transformed further to lactams in good yields.     

Palladium(II)-catalyzed heterocyclisation of 8-arylethynyl-1,2,3,4-tetrahydroquinolines: a facile route to 2-aryl-5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinoline derivatives

Dihydropyrroloquinolines have been synthesized reacting 8-arylethynyl-1,2,3,4-tetrahydroquinolines in the presence of palladium(II) chloride catalyst. Heteroannulation has been achieved in good yields and tolerates substituents on the tetrahydroquinoline, including bromo, cyano, and ester.     

Copper(I) catalysis: Synthesis of N,N′-diarylated and N-aryl,N′-formylated chiral C2-symmetric diamines

Chiral N,N′-diaryl C₂-symmetric diamines and N-aryl,N′-formyl-trans-(1R,2R)-diaminocyclohexane are readily accessed by copper catalyzed N,N′-diarylation and N-aryl,N′-formylation of trans-(1R,2R)-diaminocyclohexane with aryl bromides. N,N′-diarylation using (R)-1,1′-binaphthyl-2,2′-diamine and iodobenzene gave the corresponding (R)-N,N′-diphenyl-1,1′-binaphthyl-2,2′-diamine derivative in 83% yield.     

Unprecedented conversion of (Z)-3-chloro-3-arylacrylic acids to benzoic acids: synthesis of s-triazolo[3,4-b][1,3,4]thiadiazoles

An unprecedented method for the conversion of (Z)-3-chloro-3-arylacrylic acids to corresponding benzoic acids by stirring in POCl₃ at 80 °C is reported. The benzoic acids formed in situ undergo condensation with 4-amino-5-aryl-3-mercapto-1,2,4-triazoles to yield s-triazolo[3,4-b][1,3,4]thiadiazoles in high yields.     

Pheromone synthesis. Part 244: Synthesis of the racemate and enantiomers of (11Z,19Z)-CH503 (3-acetoxy-11,19-octacosadien-1-ol), a new sex pheromone of male Drosophila melanogaster to show its (S)-isomer and racemate as bioactive

The enantiomers of (11Z,19Z)-3-acetoxy-11,19-octacosadien-1-ol were synthesized from the enantiomers of 3,4-epoxy-1-butanol PMB ether. Its racemate was also synthesized. Its (S)-isomer and racemate were shown to possess the same pheromone activity as CH503, a long-lived inhibitor of male courtship in Drosophila melanogaster, although the racemate was less active.     

Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

A Pd₂dba₃/P(i-BuNCH₂CH₂)₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.     

Ikirydinium A: a new indole alkaloid from the seeds of Hunteria umbellata (K. Schum)

Chemical investigations into samples of Hunteria umbellata (K. Schum) collected in Osun State, Nigeria, led to the discovery of a new indole alkaloid, ikirydinium A, featuring an unprecedented 3-alkylpyridinium-indole-2-carboxylate scaffold. Ikirydinium A was found to exhibit antimicrobial activity (IC₅₀ 0.6 μM) against Bacillus subtilis ATCC 6051. The involvement of a common intermediate in the biosynthesis of ikirydinium A and vinblastine is hypothesized.