Concerning the Solvent Effect in the Aldol Condensation

Summary.  Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring α,β-unsaturated carbonyl compounds in alcoholic solvents or β-hydroxyl carbonyl compounds in tetrahydrofuran. Received November 22, 1999. Accepted (revised) December 21, 1999     

Thermal behavior of isotactic polypropylene in different content of β-nucleating agent

The effects of non-isothermal and isothermal crystallization on the formation of α- and β-phase in isotactic polypropylene (iPP) with different content of β-nucleating agent are investigated by differential scanning calorimetry (DSC). On non-isothermal crystallization, the content of β-phase and regularity of its crystals are depended on both cooling rate and the content of β-nucleating agent. The faster cooling rate is, the lower of melting peak temperature (T_mp) and crystallization peak temperature (T_cp) of α- and β-phase are. The enthalpy of fusion (∆H) of β-phase increases with cooling rate in a certain range for the sample with 0.1 wt% β-nucleating agent (G₁) and decreases for that with 0.3 wt% β-nucleating agent (G₃). On isothermal crystallization, the enthalpy of fusion of β-phase in G₁ is higher than in G₃ which is related to the efficiency of nucleation in different concentration of nucleating center in two samples.     

A correction function to determine the β-fusion heat in a mixture of α- and β-PP

Blends of known amounts of α- and β-PP crystals were prepared from pure α- and pure β-PPsamples. Their fusion behaviours were studied by differential scanning calorimetry (DSC).The fusion heats of the α- and β-crystals were approximated from the DSC curves and compared with those calculated on the basis of the compositions of the blends. A correction function was found which improved the accuracy of the respective fusion heats significantly from the DSC analysis. The correction function can be used to determine the respective fusion heats of a PP sample which contains an unknown mixture of the α- and β-crystals. This revised version was published online in July 2006 with corrections to the Cover Date.     

A modulated dsc study on the strain-induced βα-transformation in a β-form isotactic polypropylene

The mechanical strain-induced βα-transition of a β-phase isotactic polypropylene (β-iPP) was studied by modulated differential scanning calorimetry (MDSC). Samples were taken after tensile fracture of a double notched specimen from its process and plastic zones, respectively, and the related calorimetric response was compared to that of the bulk material. In contrast to conventional DSC results, it was found that the βα-transformation was not completed in the process zone. Furthermore, the melting of the α-iPP showed both non-reversing and reversing characteristics, whereas the melting of the β-phase proved to be a reversing process. Therefore, it was recommended to consider the conversion grade of the βα-transformation by the relative change in the melt flux of the reversing β-melting peak. This work was supported by the German Science Foundation (DFG-Ka 1202/4-1).     

Synthesis of Imidazo[1′,5′:1,2]pyrido[3,4-b]indole Derivatives

Summary.  The reactions of 1,2,3,4-tetrahydro-β-carboline-1-carboxylic acid and its ethyl ester with alkyl and aryl isothiocyanates under mild conditions resulted in the corresponding thiohydantoin-fused tetrahydro-β-carbolines. Treatment of the ethyl ester with isocyanates furnished ethyl 2-alkyl- or arylcarbamoyl-1,2,3,4-tetrahydro-β-carboline-1-carboxylates which were transformed to hydantoin-fused tetrahydro-β-carbolines. The structures of the thiohydantoin compounds, involving two conformers and the presence of keto-enol tautomerism, were determined by NMR spectroscopy. Corresponding author. E-mail: fulop@pharma.szote.u-szeged.hu Received February 2, 2002. Accepted (revised) March 4, 2002     

Synthesis of 6-chloronicotinates of steroidal 3β,5α,6β-triols and 3β,5-dihydroxy-6-ketones

New esters of 3β,5α,6β-trihydroxysteroids and 3β,5-dihydroxy-6-ketosteroids containing 6-chloropyridine groups characteristic of the alkaloid epibatidine were synthesized by acylation with 6-chloronicotinoylchloride. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 175-179, March-April, 2009.     

Synthesis of new α-chloropyridine derivatives of steroidal 3β,5α,6β-triols and 3β,5-dihydroxy-6-ketones

New steroid derivatives containing 6-chloropyridine groups characteristic of the alkaloid epibatidine and neonicotinoid insecticides were synthesized by reacting 3β,5α,6β-trihydroxysteroids or 3β,5-dihydroxy-6ketosteroids with 2-chloro-5-chloromethylpyridine. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 180-182, March-April, 2009.     

N-Alkylated Derivatives of 1,5-Dideoxy-1,5-iminoxylitol as β-Xylosidaseand β-Glucosidase Inhibitors

Summary.  A range of lipophilic derivatives of the D-xylosidase inhibitor 1,5-dideoxy-1,5-iminoxylitol was synthesized by N-alkylation of the parent compound with different alkyl halides. Inhibitory activities of the products obtained were measured with β-glucosidase from Agrobacterium sp., a family 1 enzyme, as well as with β-xylosidase from Thermoanaerobacterium saccharolyticum belonging to family 39 of the glycohydrolases. Whereas the former enzyme, which has low β-xylosidase activity, was only moderately inhibited, with K _i values in the millimolar range, good inhibition was observed with the latter one. Inhibitors with terminally functionalized N-alkyl chains open up opportunities for novel applications as affinity ligands as well as for various types of tagging for diagnostic purposes. Received October 25, 2001. Accepted November 19, 2001     

Chemical Components of <Emphasis Type="Italic">Leptopus chinensis</Emphasis>

Six substances were isolated from the branches and leaves of the Chinese herb Leptopus Chinensis (Bunge) Pojark. by column chromatography for the first time. Their structures were elucidated as 3α-hydroxyfriedelan-2-one, saccharose, triacontanol, friedelane-2α,3β-diols, β-sitosterol-3-O-β-D-glucoside, and β -sitosterol on the basis of x-ray, chemical, and spectroscopic methods. __________ Published in Kimiya Prirodnikh Soedinenii, No. 5, pp. 462–464, September–October, 2005.     

ZrCl4-Catalyzed Efficient Synthesis of Enaminones and Enamino Esters under Solvent-free Conditions

Summary. A facile synthesis of β-enaminones and enamino esters by condensation of β-dicarbonyl compounds with differently substituted amines in the presence of ZrCl₄ under solvent-free conditions is reported.     

A highly active fungal β-glucosidase

A highly active thermostable β-glucosidase was purified to homogeneity from a strain ofTrichoderma sp. The enzyme was an extracellular glycoprotein and showed hydrolytic activity toward several β-glucosides. Cellobiose was found to be the substrate of choice for this enzyme. This finding could suggest future technological applications of the purified protein.     

Diastereodirected Synthesis of 1-Aryl-4-phenyl-β-carbolines

A diastereodirected Pictet-Spengler reaction has been carried out to give the previously unknown 1-aryl(alkyl)-4-phenyl-β-carbolines and it has been found that all of the β-carbolines diastereomers obtained have predominantly the R*,R*-configuration. The diastereoselectivity of the given reaction is 44–70%. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1521–1528, October, 2005.     

On the Reaction between 1-Aza-1,3-dienes and Push-Pull Olefins of the Acyloxymethylidene-malononitrile Type

Summary.  The reaction between push-pull olefins of the acyloxymethylidene-malononitrile type and α, β-unsaturated hydrazones affords selectively 5-alkyl-2-cyano-6-(N′,N′-dimethylhydrazono)-hexa-2,4-dienenitriles. No [4+2]-cycloaddition products were detected. The structure elucidation of the obtained compounds and possible reaction mechanisms are discussed. Received March 9, 2000. Accepted March 20, 2000     

Polymeric adsorbents with peptide pendants as artificial receptors for β-lactam antibiotics by mimicking the binding sites of β-lactamases

A series of polymeric adsorbents with peptide pendants were designed as the artificial receptors of β-lactam antibiotics by mimicking the structures of binding site in β-lactamases. Crosslinked poly(N, N-dimethyl acrylamide) gel as a carrier was prepared by suspension copolymerization of N, N-dimethyl acrylamide and N. Ń-bisacryl-diaminoethane and then functionalized with ethylenediamine after partial hydrolysis. Using solid-phase peptide synthesis with symmetrical anhydride of protected amino acid step by step, various peptide pendants were respectively anchored onto the functionalized carrier. The adsorption properties of these peptide-containing adsorbents for β-lactam antibiotics such as ampicillin and cefotaxime were then studied. The results showed that only those adsorbents in which peptide chains contained more than one lysine residues could obviously adsorb both β-lactams and that static interaction as well as hydrogen bond played an important role during the adsorption. Project supported by the National Natural Science Foundation of China (No. 59493207).     

Grafting of cyclodextrins onto filter paper

Grafting of cyclodextrins and cyclodextrins derivatives on cellulosic surface, such as paper or filter paper, provides hosting cavities that can include a large variety of chemicals for specific cellulose finishing. In this study grafting of monocholorotriazinyl-β-cyclodextrin (MCT-β-CD) and β-cyclodextrin (β-CD) to filter paper has been performed. β-cyclodextrin has been bonded to filter paper using 1,4-butanediol diglycidyl ether as the crosslinking agent. The untreated and treated filter papers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), demonstrating the covalent binding of cyclodextrins to filter paper. The quantification of β-CD and MCT-β-CD grafted to filter paper was determined by the dye extinction method with the inclusion of phenolphthalein. The final β-CD content amounted to 15.9 μmol per gram of support (1.8% by weight), and 72.8 μmol per gram of support (11.3% by weight) for MCT-β-CD.     

Free-radical reactions of methyl trifluoropyruvate with aldehydes

Methyl trifluoropyruvate reacts with aldehydes in the presence of catalytic amounts of benzoyl peroxide at 130–140°C to give β,β,β-trifluoro-α-(methoxycarbonyl)ethyl carboxylates. UV irradiation makes oligomerization of the initial ketoester predominant. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1763–1766, September, 1998.     

Purification and Characterization of an Intracellular β-Glucosidase from Lactobacillus casei ATCC 393

The lactic acid bacterium,Lactobacillus casei, produces an intracellular β-glucosidase when grown on Man-Rogosa-Sharpe (MRS) medium with cellobiose as carbon source. The β-glucosidase activity is produced intracellulary, and no extracellulary activity was detected. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase as estimated by gel filtration was 480 kDa, consisting of six probably identical subunits. The enzyme exhibited optimum activity at 35°C and pH 6.3 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with (1→4)-β configuration and from Lineweaver Burk plots, K_m value of 16 mmol/L was found for β-pNPG. The β-glucosidase was competitively inhibited by glucose, and no glycosyl transferase activity was observed in the presence of ethanol.     

Staudinger Reaction of Schiff Bases of Acetylthiophene and Acetylpyridine with Ketenes. Diastereoselective Synthesis of 4-Heterosubstituted β-Lactams and their Conversion to β-Thiolactams

Summary. Arylimines of 2-acetylthiophene and 2-, 3-, and 4-acetylpyridines react with ketenes yielding 4-heterosubstituted β-lactams. Reactions of imines with ketenes were proved to be diastereoselective. The stereochemistry of the products was confirmed by X-ray analysis. β-Lactams treated with Lawesson’s reagent gave β-thiolactams.     

Synthesis of perfluoroalkyl-containing tri-and tetradentate β-amino enones

Reactions of perfluoroalkyl-containing aliphatic 1,3-diketones with triethyl orthoformate afforded a number of β-ethoxy enones. Their reactions with o-phenylenediamine gave novel perfluoroalkyl-containing tridentate β-amino enones and tetradentate bis(β-amino enones) in high yields. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2086–2092, September, 2005.