Chemical constituents of the essential oils of Sideritis scardica Griseb. and Sideritis raeseri Boiss and Heldr. from Bulgaria and Macedonia

The essential oils of two species of Sideritis growing spontaneously in Bulgaria and Macedonia are reported, Sideritis scardica and Sideritis raeseri. The oils of S. scardica from different locations differed significantly: in the Macedonian sample alpha-cadinol (20%) predominated, while in the oil of Bulgarian samples the main components were diterpenic compounds and octadecenol (over 20%). This is the first report of ditrpenoids in essential oil of S. scardica. The oil of S. raeseri demonstrated a distinct chemical profile with its high concentration of sesquiterpenes, main components being germacrone (25%) and elemol acetate (15.9%). The observed qualitative variability of the oil composition of S. scardica of different geographic origin could be a result of different ecologic conditions but might also reflect the well-known tendency of some Sideritis species to hybridize.     

Hydrogenation/Regioselective C‐Acylation Reaction of Diethyl Coumarin‐3‐phosphonate With NaBH4/Acid Anhydrides: A New One‐Pot Tandem Reaction

The one‐pot tandem reaction of diethyl coumarin‐3‐phosphonate 1 with a mixture of sodium borohydride/acid anhydrides gives mainly the corresponding hydrogenation/acylation product of diethyl 3‐acyl‐2‐oxochroman‐3‐ylphosphonates 3a–d in good yields. Different experimental conditions have been examined to get the best yields of the reaction products. From this reaction the hydrogenation product of diethyl 2‐oxochroman‐3‐ylphosphonate, 2, as well as the products of the consecutive hydrogenation, diethyl 2‐hydroxychroman‐3‐ylphosphonate (4) and diethyl 3‐[2‐hydroxyphenyl]‐1‐hydroxy‐propan‐2‐ylphosphonate (5), have been isolated.     

Chemical Structure and In Vitro Antitumor Activity of Rhamnolipids from Pseudomonas aeruginosa BN10

A newly isolated indigenous strain BN10 identified as Pseudomonas aeruginosa was found to produce glycolipid (i.e., rhamnolipid-type) biosurfactants. Two representative rhamnolipidic fractions, RL-1 and RL-2, were separated on silica gel columns and their chemical structure was elucidated by a combination of nuclear magnetic resonance and mass spectroscopy. Subsequently, their cytotoxic effect on cancer cell lines HL-60, BV-173, SKW-3, and JMSU-1 was investigated. RL-1 was superior in terms of potency, causing 50 % inhibition of cellular viability at lower concentrations, as compared to RL-2. Furthermore, the results from fluorescent staining analysis demonstrated that RL-1 inhibited proliferation of BV-173 pre-B human leukemia cells by induction of apoptotic cell death. These findings suggest that RL-1 could be of potential for application in biomedicine as a new and promising therapeutic agent.     

Selective amidoalkylation of cyclic enamino ketones with N-acyliminium salts of 3,4-dihydroisoquinolines

A series of cyclic enaminoketones were selectively amidoalkylated at the α-carbon in reactions with acyliminium reagents derived from 3,4-dihydroisoquinolines.     

Catalytic performance of Ni-Al layered double hydroxides in CO purification processes

Ni-Al layered double hydroxides with Ni²⁺/Al³⁺ molar ratios of 1.5 and 3.0 have been synthesized by co-precipitation and studied as catalyst precursors for purification of CO-containing gas-mixtures by means of CO oxidation to CO₂ and conversion of CO by water vapor (water-gas shift reaction). The influence of the alkali additives (K⁺ ions) on the water-gas shift activity has been also examined. It was established that the catalytic activity of both reactions increases with the temperature and the nickel content. Hypothetic schemes are proposed about activation of the catalysts in the WGSR and CO oxidation including redox Ni²⁺ ? Ni³⁺ transition on the catalyst surface. The activity in WGSR is positively affected by the presence of potassium promoter, depending on its amount. The sample with higher nickel loading is the most effective catalyst as for CO oxidation as well as for WGSR at intermediate temperatures after potassium promotion.     

Crystal structure of a new small-pore zirconosilicate Na2ZrSi2O7·H2O and its relation to stoichiometrically and topologically similar compounds

The small-pore zirconosilicate Na₂ZrSi₂O₇·H₂O crystallizes in monoclinic system with space group C2/c, a = 5.4715(4); b = 9.4111(6); c = 13.0969(8) Å, β = 92.851(7)°. Its framework consists of layers built of ZrO₆ octahedra and SiO₄ tetrahedra and forming condensed [Si₂O₇] pyrogroups by connection. The sodium ions and water molecules are placed in channels set up between the layers. The stoichiometric and structural similarities of the studied phase with anhydrous compounds having general chemical formula A₂₍₃₎MT₂O₇ (A = Na,K; M = Zr,Lu,Sc; T = Si,Ge) are discussed. The topological relationship of their structures is interpreted in the light of spatial combination of silicon and zirconium polyhedra as basic building units into larger composite building units and their three-dimensional arrangement.     

The state of nickel in the silver modified NiMg/SiO<Subscript>2</Subscript> vegetable oil hydrogenation catalysts

Two series of silver modified Ni-Mg materials were synthesized by precipitation-deposition on SiO₂ support derived from two silica sources: diatomite activated at 800°C (Series a; Mg/Ni = 0.1 and SiO₂/Ni = 1.07) and synthetic water glass (Series b; Mg/Ni = 0.1 and SiO₂/Ni = 1.15). The modification with silver was made at three molar Ag/Ni ratios, namely 0.0025, 0.025, and 0.1. The effects of the source of the silica support and the silver presence and content on the nickel state in the silver modified reduced-passivated NiMg/SiO₂ precursors of the vegetable oil hydrogenation catalyst were established by X-ray diffraction and X-ray photoelectron spectroscopy techniques. The passivation procedure was applied in order to protect the metallic nickel particles from further oxidation. The crystallization of the formed nickel hydrosilicate phases depends on the source of the silica support, more expressed in the diatomite supported samples. It was shown that the silver modification of the NiMg/SiO₂ precursors enhances the reduction of the nickel hydrosilicates accompanied by formation of relatively smaller metallic nickel particles, more pronounced in the water glass supported precursors. The increase of the silver content in the water glass deposited samples is responsible for the metallic nickel dispersion increase. The higher content of the Ni⁰ particles on the surface of the diatomite deposited samples is in accordance with the higher stability of the larger metallic nickel crystallites to oxidation during the passivation step. On contrary, higher dispersed Ni⁰ particles on the surface of the water glass supported samples are more susceptible to the oxida The article is published in the original.     

A new and efficient method for the synthesis of 3,4-disubstituted pyrrolidine-2,5-diones

A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxy-pyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.