A universal temperature controlled membrane interface for the analysis of volatile and semi-volatile organic compounds

A universal temperature controlled membrane interface (TCMI) has been constructed for hollow-fibre membranes. The membrane temperature is controllable in the range -70 to 250 degrees C using an electric heater and a flow of cooled nitrogen or helium gas. Volatile and semi-volatile organic compounds may be detected either by continuous diffusion across the membrane or by in-membrane pre-concentration followed by thermal desorption into the detector. The TCMI interface is demonstrated in combination with mass spectrometry and GC-MS, for the determination of VOCs and SVOCs in aqueous and air samples and for the on-line monitoring of a bioreactor.     

New taxane derivatives: synthesis of baccatin[14,1-d]furan-2-one nucleus and its condensation with the norstatine side chain

New taxanes 15 and 18, containing the unsaturated and saturated baccatin[14,1-d]furan-2-one nucleus, respectively, were prepared starting from the readily available 13-oxo-7-Tes-baccatin III (3). Sequential formation of the enolate of 3 and reaction with ethyl glyoxylate gave the 13-oxo-7-Tes-baccatin[14,1-d]-3,4-dehydrofuran-2-one 4. The reduction of 4 can result in the formation of a mixture of compounds corresponding to 13-hydroxy alcohol 5 and 13-enol derivative 6. Both 5 and 6 were transformed into 13-oxo-7-Tes-baccatin[14,1-d]furan-2-one 8 by treatment with a base. Further reduction of 8 gave 13-hydroxy compound 9. Esterification of 6 and 9 with N,O-protected norstatine 12, followed by deprotection, gave the new promising anticancer taxanes 15 and 18, respectively.     

Comparative receptor mapping of serotoninergic 5-HT3 and 5-HT4 binding sites*

The clinical use of currently available drugs acting at the5-HT₄ receptor has been hampered by their lack of selectivityover 5-HT₃ binding sites. For this reason, there is considerableinterest in the medicinal chemistry of these serotonin receptor subtypes, andsignificant effort has been made towards the discovery of potent and selectiveligands. Computer-aided conformational analysis was used to characterizeserotoninergic 5-HT₃ and 5-HT₄ receptorrecognition. On the basis of the generally accepted model of the5-HT₃ antagonist pharmacophore, we have performed a receptormapping of this receptor binding site, following the active analog approach(AAA) defined by Marshall. The receptor excluded volume was calculated as theunion of the van der Waals density maps of nine active ligands(pK_i 8.9), superimposed in pharmacophoric conformations.Six inactive analogs (pK_i < 7.0) were subsequently used todefine the essential volume, which in its turn can be used to define theregions of steric intolerance of the 5-HT₃ receptor. Five activeligands (pK_i 9.3) at 5-HT₄ receptors wereused to construct an antagonist pharmacophore for this receptor, and todetermine its excluded volume by superimposition of pharmacophoricconformations. The volume defined by the superimposition of five inactive5-HT₄ receptor analogs that possess the pharmacophoric elements(pK_i 6.6) did not exceed the excluded volume calculated forthis receptor. In this case, the inactivity may be due to the lack of positiveinteraction of the amino moiety with a hypothetical hydrophobic pocket, whichwould interact with the voluminous substituents of the basic nitrogen ofactive ligands. The difference between the excluded volumes of both receptorshas confirmed that the main difference is indeed in the basic moiety. Thus,the 5-HT₃ receptor can only accommodate small substituents inthe position of the nitrogen atom, whereas the 5-HT₄ receptorrequires more voluminous groups. Also, the basic nitrogen is located at ca.8.0 Å from the aromatic moiety in the 5-HT₄ antagonistpharmacophore, whereas this distance is ca. 7.5 Å in the5-HT₃ antagonist model. The comparative mapping of bothserotoninergic receptors has allowed us to confirm the three-componentpharmacophore accepted for the 5-HT₃ receptor, as well as topropose a steric model for the 5-HT₄ receptor binding site. Thisstudy offers structural insights to aid the design of new selective ligands,and the resulting models have received some support from the synthesis of twonew active and selective ligands: 24 (K_i(5-HT₃)= 3.7 nM; K_i(5-HT₄) > 1000 nM) and 25(K_i(5-HT₄) = 13.7 nM;K_i(5-HT₃) > 10 000 nM).     

Electrosynthesis of 3-chloro-1,4-disubstituted-2(1H)- quinolinones and 3,3-dichloro-4-hydroxy-1,4-disubstituted- 3,4-dihydro-2(1H)-quinolinones,as well as a new convenient process to dioxindoles

Cathodic reduction of N-(2-acyl(or aroyl)phenyl)-2,2,2,-trichloro-N-alkylacetamide at -1.2 V (vs SCE) under aprotic conditions yields 3-chloro-1,4-disubstituted-2(1H)-quinolinones (1) as the major product. When the reaction is carried out at -0.8 V (vs SCE), 3,3-dichloro-4-hydroxy-1,4-disubstituted-3,4-dihydro-2(1H)-quinolinones (2) and 1,4-disubstituted-1,4-dihydro-quinoline-2,3-dione (3) are formed. Ring contraction of 2 and 3 in aqueous sodium hydroxide resulted in the formation of 3-hydroxy-1,3-dihydroindol-2-ones (5). The most plausible reaction mechanisms are proposed.     

Agro-industrial waste enzymes: Perspectives in circular economy

According to the Food and Agriculture Organization of the United Nations, approximately 1.3 billion tons of food is wasted each year, equivalent to approximately one-third of world production. Agri-food wastes are the source of proteins, carbohydrates, lipids, and other essential minerals that have been exploited for value-added products by the development of biorefineries and sustainable business as important elements of circular economies. The innovation and materialization of these types of processes, including the use of disruptive technologies on microbial bioconversion and enzyme technology, such as nanotechnology, metabolic engineering, and multi-omics platforms, increase the perspectives on the waste valorization process. Lignocellulolytic enzymes, pectinases, and proteases are mainly used as catalyzers on agri-food waste treatment, and their production in house might be the trend in near future for agro-industrial countries. Another way to transform the agri-food wastes is via aerobic or anaerobic microbial process from fungal or bacterial cultures; these processes are the key to produce waste enzymes.     

Paired electrosynthesis of cyanoacetic acid

Cyanoacetic acid is formed by cathodic reduction of CO(2) and anodic oxidation of the tetraalkylammonium salt anion; the process is conduced in acetonitrile using a divided cell with a medium porosity glass-frit diaphragm. A mechanism for this paired electrochemical reaction is proposed.     

Cyclization and rearrangement of diterpenoids. VII. Composition of the hydrocarbon fraction of a mixture of the products of cyclization of manool and sclareol by ordinary acids

The hydrocarbon fractions of the products of the cyclization of manool and sclareol by a mixture of conc. sulfuric and formic or acetic acids have been investigated. It has been established that they contain, in addition to the ⁸/⁹-pimaradiene, ⁸(⁹)-isopimaradiene, roasadiene, and 13-epirosadiene identified previously, the tetracyclic hydrocarbons (1R, 2S, 7S, 11S, 12R, 13R)-2, 6, 6, 11, 13-pentamethyl-tetracyclo [10.2.1.0^1.10.0^2.7] pentadeca-9-ene and (1S, 2R, 11S, 12R, 1R)-2, 7, 7, 11, 15-pentamethyltetracyclo[10.2.1.0^2.11.0^3.8] pentadeca(8)-ene.Institute of Chemistry of the Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinii, No. 5, pp. 719–721, September–October, 1988.     

Synthesis, structure and properties of ruthenium(II) complexes with quinolinedione derivatives as chelate ligands: Crystal structure of [Ru(CO)2Cl2(6-methoxybenzo[g]quinoline-5,10-dione)]

The reaction of the dimer complex [{Ru(CO)₃Cl₂}₂] with the ligands 4,6-dichloroquinoline-5,8-dione and 6-methoxybenzo[g]quinoline-5,10-dione in ethanol solution led to the neutral mononuclear complexes of general formula [Ru(CO)₂Cl₂(κ²-quinolinedione-N,O)]. The complexes were characterized by elemental analysis, IR and RMN spectroscopy, and the molecular structure of [Ru(CO)₂Cl₂(6-methoxybenzo[g]quinoline-5,10-dione)] was determined by single-crystal X-ray diffraction. The redox chemistry of ligands and complexes was investigated by cyclic voltammetry, and their potential antitumor activity was also evaluated.     

Synthesis and NMR characterization of 3,4′-dibutoxy-2,2′-bithiophene

3,4′-Dibromo-2,2′-bithiophene was converted, in high yield, into the corresponding dibutoxy derivative. The ¹H ¹³C and nmr data are discussed in comparison with those of 3,3′- and 4,4′-dibutoxy-2,2′-bithiophene in relation to regiochemistry.