The first synthesis of ent-agelasine F

Agelasine F has previously been isolated from marine sponges (Agelas sp.) and has been associated with various bioactivities including inhibitory activity on Mycobacterium tuberculosis. No total synthesis of this natural product has been reported. ent-Agelasine F has now been synthesized for the first time, starting from (R)-pulegone. The synthesis is considerably more efficient than a previously reported route to rac-agelasine F. ent-Agelasine F is found to exhibit antimicrobial activity.     

Cinetique de polymerisation du styrene en presence de peroxyde de benzoyle p,p′ bis-bromomethyle synthese de polymeres peroxydes

The free radical polymerization of styrene has been studied by using p,p′-bisbromomethyl benzoyl peroxide as initiator containing a chain transfer group. The rate constant of decomposition (k_d) of this peroxide has been determined at various temperatures, as well as the efficiency factor f and the transfer constant to initiator C₁. At 60°, f = 0·70 ± 0·05 and C₁ = 0·5. Polystyrene containing peroxide groups has been prepared by using this initiator. The highest yield in polymeric peroxide has been obtained for polymerization in emulsion at 40°.     

Lipase-catalyzed resolution of chiral 1,3-amino alcohols: application in the asymmetric synthesis of (S)-dapoxetine

The enzymatic resolution of 3-amino-3-phenylpropan-1-ol derivatives has been studied through acylation processes. Candida antarctica lipase A (CAL-A) has been identified as the best biocatalyst for the transesterification reaction of 3-amino-3-phenyl-1-tert-butyldimethylsilyloxy-propan-1-ol using ethyl methoxyacetate as acylating agent and tert-butyl methyl ether as solvent. This enzymatic study has allowed us to obtain a valuable intermediate for the production of (S)-dapoxetine, which has been synthesized in good overall yield and high enantiomeric excess.     

Conductivity behaviour of proton conducting polymer gel electrolytes with PVdF-HFP

Electrical conductivity of polymer gel electrolytes containing different hydroxy substituted benzoic acids and polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) has been studied. The conductivity of solution and gel electrolytes shows ortho effect and has been found to depend upon the acidity constant of the acid used and varies as σ (ortho-) > σ (meta-) > σ (para-). The addition of PVdF-HFP to solution electrolytes results in an increase in conductivity and the conductivity of gel electrolytes has been found to be higher than that of the corresponding liquid electrolytes for all the three acids studied i.e. σ (gel) >σ (liquid). The increase in conductivity with polymer addition has also been found to depend upon the acid concentration.     

The molecular structure of 1-methyl-trans-cyclooctene

The molecular structure of 1 -methyl-trans-cyclooctene has been studied by the gas electron diffraction method. A molecular mechanics calculation has been done for the title compound and for trans-cyclooctene and 1,2-dimethyl-trans-cyclooctene.     

The nπ* states of the thiocarbonyl halides: The ā3A ← X̄1A' electronic transition in thiocarbonyl chlorofluoride

The visible absorption spectrum of thiocarbonyl chlorofluoride, C1FCS in the 495-nm region has been observed in the vapour phase under conditions of high resolution and pressure x path-length and has been assigned to the ā³A'' (n, π^*) ← X?¹A' electronic transition. Three of the six fundamental modes have been assigned for the upper electronic state. Prom a fit of the observed levels in v¹_o (the out-of-plane wagging mode) to the eigenvalues obtained from a quadratic-gaussian potential, the barrier to inversion in the ā³A state has been evaluated to be 1622 cm^?1 The electronic effects of replacing a sulphur by an oxygen atom on the height of the barrier to inversion in the nπ^* carbonyl and thiocarbonyl halides have been explored by the CNDO/2 method. The much lower barriers in the thiocarbonyl compounds has been attributed to the sulphur d_xz AO which is not present in the carbonyl compounds. This AO, which has relatively high weight in the LCAOs which form the π^* MO, has the effect of relieving some of the antibonding density which resides on the carbon atom and thereby reduces the barrier to inversion.     

Thermal copolymerization of acrylonitrile with methacrylate units arranged in matrix

Copolymerization of acrylonitrile with methacrylates on a matrix has been examined (using methacrylate of p-cresol-formaldehyde resin). It has been found that the copolymerization proceeds at 70° without an initiator. The reactivity ratios depend on the length of the matrix used. The method of calculating Q and e according to the Alfrey-Price scheme has been discussed for the system under investigation.     

Reactions of chloroalkyl-gem-dichlorocyclopropanes with amines

N-Alkylation of primary and secondary amines with monochloroalkyl-gem-dichlorocyclopropanes under conditions of thermal and microwave heating results in the corresponding amino-gem-dichlorocyclopropanes. With microwave irradiation heating, the reaction time has been decreased to 1 h, the yields of the amines containing gem-dichlorocyclopropane moiety being the same. Formation of the bicyclic amine in reaction of cis-2,3-dichloromethyl-gem-dichlorocyclopropane with primary amines under conditions of phasetransfer catalysis has been studied.     

Synthesis and transport studies of new enantiopure lipophilic crown ethers containing a diarylphosphinic acid unit

The synthesis of new enantiopure lipophilic crown ethers (S,S)-6, (R,R)-6 and (S,S)-7 containing a diarylphosphinic acid unit has been carried out. The transport ability of these ligands has been studied in an aqueous source phase/lipophilic organic bulk liquid membrane/aqueous receiving phase system controlled by the pH of the media. The transport of metal ions and amines has also been studied. These studies showed high selectivity for protonated amines.     

Metal-catalysed radical cyclisations leading to N-heterocycles: new approaches to gabapentin and pulchellalactam

The copper(I) or ruthenium(II)-mediated radical cyclisation of halo-amides has been utilised to afford functionalised pyrrolidinones via 5-endo-trig or 5-exo-trig radical cyclisation pathways. This methodology has been applied to novel and concise syntheses of the anti-epileptic drug gabapentin and the biologically active natural product pulchellalactam.     

Synthesis and PMR properties of some dehydroalanine derivatives

A number of new β-N-alkylamino acids have been synthesised from N-acetyldehydroalanine, and their chromatographic and PMR properties examined. A selected peptide S-DNP-glutathione has also been subjected to alkaline degradation and the formation of dehydroglutathione has been shown by PMR.     

Prediction of permselectivity of nitrate and acetate ions in the electrodialysis of aqueous solutions

Electrodialysis of aqueous solutions of acetic and nitric acids encountered in the industrial practice of deacidification of raw glyoxal solutions has been carried out to investigate the permselectivity of the system. The dependence of the permselectivity coefficient τ on experimental parameters such as flow velocity (V), current density (I), concentration of anions (C_i), etc. has been evaluated. A correlation between τ and the critical parameters has been obtained. Well-known theoretical equations have been used to calculate τ at limiting current density I_lim and as I approaches zero. Calculated results are compared with observed values. Limitations of theoretical procedures when applied to a system containing a weak acid are explained.     

On the Use of Monolithic Sol–Gel Derived Mesoporous Silica for the Calibration of Thermoporisemetry Using Various Solvents

Sol–gel derived mesoporous monolithic silica gels have been prepared to be used as standard materials for thermoporosimetry. The technique has been calibrated with n-heptane and cyclohexane and R _p = f(Δt) and W _a = f(ΔT) expressions are derived. In the specific case of cyclohexane, the solid to solid phase transition has been used. It is also shown that porous volumes can be measured by thermoporosimetry and that the correlation with N₂ gas sorption results is very good. Finally, thermoporosimetry has been applied to the study of cross linking level in polyisoprene samples containing a gradient of cross linking agent.     

Synthetic approach toward cis-disubstituted γ- and δ-lactones through enantioselective dialkylzinc addition to aldehydes: application to the synthesis of optically active flavors and fragrances

A versatile and straightforward approach to optically active cis-4,5-disubstituted γ- and δ-lactones by catalytic enantioselective addition of dialkyzincs to cinnamic aldehydes and RCM ring closure has been reported. The synthetic importance of the enantioselective dialkylzinc alkylation of aldehydes has been thus widened. Such an approach has then been employed for the enantioselective synthesis of naturally occurring γ-lactone flavors like (S)-5-ethyl-butanolide (6a) and (4S,5S)-cis-whisky lactone (6b) and extended to the preparation of δ-lactones like (5S,6S)-5-methyl-6-ethylpentanolide (9a), precursor of the pheromone serricornin.     

A new method of synthesis of substituted 1-(1H-imidazole-4-yl)-1H-1,2,3-triazoles and their fungicidal activity

Based on the deoxygenation reaction of 1-(1-tert-butyl-3-nitroazetidine-3-yl)-1H-1,2,3-triazoles a new method for the synthesis of substituted 1-(1H-imidazole-4-yl)-1H-1,2,3-triazoles has been developed. Fungicidal activity of these compounds has been investigated at a range of phytopathogenic fungi.     

Novel growth methods of optoelectronic crystals based on antimonides

This work contributes to the growth of bulk crystals where crystals are grown from a molten-solution zone (MSZ). Our original modifications ofTHM have been used for a crystallization of GaSb and of (Ga.In)Sb—the ternary Solid Solution (TSS). The crystallization process has been accelerated with a low frequency and low energy vibrational stirring (VS). Lately, the stirring has been combined with the magneto-hydrodynamical stirring (MHD-S) and applied on GaSb. The lattice parameter ‘a’ ofTSS crystals has been constant throughout the significant part of the ingot length. This approach has permitted the growth of these crystalline ingots with ‘a’ apriori chosen and calculated—having the deviation from its constancy less than 0.03% (0.2 pm) with a 75 mm length. Crystals can have a mosaic structure at this stage.     

Electronic structure of C40 possible structures

C₄₀ is a fullerene with a conformation that has been proposed as T_d, D_2d, D_4h and D_5d symmetry groups. The correct structure has not been determined because it has not been possible to isolate the molecule, but there have been several studies of minor fullerenes that include it. In this work we present a theoretical study at the gaussian 94 HF/3-21G level that gives answers about the principal differences between the mentioned structures and the possible thermodynamic stability of each one. Furthermore, we include a similar study on the new D_2h structure that we propose.     

Desymmetric hydrogenation of a meso-cyclic acid anhydride toward biotin synthesis

Catalytic reactivity in the hydrogenation of a cyclic anhydride to a biotin synthetic intermediate has been investigated on the basis of Lyons’ original method using Wilkinson Ru complex, revealing the high performance of DPPF and XANTPHOS diphosphines possessing wide bite angles. The results have shown a new trail for design of the corresponding asymmetric catalysts, and the potential utility of (S,S)-Et-FerroTANE and (S,S)-(R,R)-Ph-TRAP has been demonstrated.     

Calix[n]arene Carboxylic Acid Derivatives as Regulators of Enzymatic Reactions: Enhanced Enantioselectivity in Lipase-Catalyzed Hydrolysis of (R/S)-Naproxen Methyl Ester

Candida rugosa lipase was immobilized with a sol–gel encapsulation procedure in the presence and absence of a calix[n]arene carboxylic acid derivative grafted onto magnetic nanoparticles or in the presence of the calix[n]arene carboxylic acid derivative with Fe₃O₄ magnetic nanoparticles as an additive. Through the enantioselective hydrolysis of racemic naproxen methyl ester and the hydrolysis of p-nitrophenylpalmitate, the relative enzyme activity was evaluated and tested. These results show that the encapsulated lipase without supports has lower conversion and enantioselectivity compared to the Calix[n]COOH-based encapsulated lipase. It has also been observed that the Calix[4]COOH-based encapsulated lipase has excellent enantioselectivity (enantiomeric ratio (E)?>?400) as compared to encapsulated-free lipase enantioselectivity (E?=?137), and it also has an enantiomeric excess value of ~98 % for S-naproxen.