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1

Low temperature synthesis of cubic phase zinc sulfide quantum dots

100%

Shahid R. , Toprak M. , Soliman H. , Muhammed M.

Open Chemistry

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2012

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tom 10

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nr 1

54-58

EN

In this study, we report on a new method for the synthesis of ZnS quantum dots (QDs). The synthesis was carried out at low temperature by a chemical reaction between zinc ions and freshly reduced sulfide ions in ethanol as reaction medium. Zinc chloride and elemental sulfur were used as zinc and sulfur sources, respectively and hydrazine hydrate was used as a strong reducing agent to convert elemental sulfur (S8) into highly reactive sulfide ions (S2−) which react spontaneously with zinc ions. This facile, less toxic, inexpensive route has a high yield for the synthesis of high quality metal sulfide QDs. Transmission electron microscopy (TEM) image analysis and selected area electron diffraction (SAED) reveal that ZnS QDs are less than 3 nm in diameter and are of cubic crystalline phase. The UV-Vis absorption spectrum shows an absorption peak at 253 nm corresponding to a band gap of 4.9 eV, which is high when compared to the bulk value of 3.68 eV revealing strong quantum confinement. PL emission transitions are observed at 314 nm and 439 nm and related to point defects in ZnS QDs.

2

Effect of microwave irradiation on polyphenolic compounds from Satureja hortensis L.

100%

Lung I. , Soran M. , Tudoran C. , Măruţoiu C.

Open Chemistry

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2013

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tom 11

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nr 4

535-541

EN

Summer savory (Satureja hortensis L.) is most often used as a culinary herb, but it also has medicinal benefits. The extracts from control and irradiated savory were obtained by ultrasound extraction for 30 minutes in an ethanol - water (80:20, v/v) mixture. Polyphenolic compounds from savory were identified and characterized by high-performance liquid chromatography coupled with a photodiode array detector and mass spectrometer. The separation was performed using an Altima C18 column (100×3 mm, 3 μm) and as mobile phase two solvent mixture: A - acetonitrile and B - water-formic acid (99.9:0.1, v/v). Peaks were identified with authentic standards in accordance to retention time, UV spectra and molecular mass. It was identified as caffeic acid, rosmarinic acid, luteolin, naringenin and apigenin. A quantitative determination of polyphenolic compounds was performed applying the external standard method. Our study showed large quantitative differences between the control plant and the irradiated plant. [...]

3

An Improved Protocol for the Preparation of New 1, 2, 3 Triazolium Based Ionic Liquids and their Application as solvent for Aldol reaction

86%

Srivastava V.

Asymmetric Catalysis

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2013

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tom 1

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nr 1

EN

Microwave heating was used to synthesise different types of 1, 2, 3 triazolium based ionic liquids (5a-j) with good yield in reduced time. These ionic liquids were further screened as reaction medium for Aldol reaction using two different most promising organocatalysts; proline and proline tetrazole. In both cases, Aldol products were obtained in good yield and selectivity with each ionic liquid. It is important to notify that all the ionic liquids (5a-j) offer 5 times recyclability with our catalytic system (Proline or Proline tetrazole).

4

Synthesis, reactions and antineoplastic activity of 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromene derivatives

86%

Gašparová R. , Koiš P. , Lácová M. , Kováčová S. , Boháč A.

Open Chemistry

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2013

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tom 11

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nr 4

502-513

EN

The key 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromen-5-yl acetates 3 were synthesized in high yields by cyclocondensation of 4-oxo-4H-chromen-3-carbaldehydes 1 with coumarin-3-acetic acids 2 under mild conditions. The reaction pathway involves aldol condensation and subsequent intramolecular lactonization to afford 2-oxo-2H,5H-pyrano[3,2-c]chromene skeleton 3. Further treatment of acetates 3 with alcohols, water or nitrogen containing compounds led to 5-alkoxy-, 5-hydroxy- or 5-acylamino-2H,5H-pyrano[3,2-c]chromen-2-ones 4-6 via nucleophilic substitution of acetyloxy group at C-5. Acetates and hydroxyl derivatives 3 and 5 undergo facile rearrangement in an acid medium yielding 5-hydroxypyrano[2,3-b]chromen-2(10aH)-ones 7. [...] Twelve prepared compounds were evaluated on their antineoplastic activities on 60 human tumour cell line panels in NCI USA. The obtained biological results confirmed that 3-(2-oxo-2H-chromen-3-yl)-2H,5H-pyrano[3,2-c]chromen-2-one represents a new leading skeleton suitable for further antitumour activity study.

5

Generation of Molecular Shape Diverstiy. From Privileged Scaffolds to Diverted Total Synthesis

72%

Dai W.-M.

Diversity Oriented Synthesis

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2012

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tom 1

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nr 1

EN

Molecular shape is a presentation of a molecule’s three-dimensional structure and its volume of space and surface electrostatic potential map collectively define the function, e. g. as a modulator or probe to biological targets. Molecular shape diversity for compound libraries with multiple scaffolds (rich skeletal diversity) is recognized as a prerequisite for discovering broad bioactivity. Established strategies and methodologies for diversity-oriented synthesis (DOS) are useful for generating molecular shape diversity by synthesizing natural product-like compounds. On the other hand, diverted total synthesis (DTS) offers natural products and analogues with a higher degree of structural diversity and complexity. Examples of DOS of privileged heterocycles and DTS of amphidinolide T marine macrolides from the author’s laboratories are illustrated.