Wyniki wyszukiwania - Biblioteka Nauki

1

stereoselective and Effective Synthesis of Alkyl alfa-D-Gluco- and alfa-D-Galactopyranosides

100%

Kasprzycka A. , Szeja W.

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2005

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tom Vol. 79 / nr 2

329-333

EN

Practical, improved synthesis of alkyl alfa-D-glycopyranosides by reaction of O-gluco- or O-galactopyranosyl N-allyl thiocarbamate with bromine followed by addition of alcohol is described. This process proceeded very fast to give the glycosides in good yields and excellent stereoselectivity.

2

Carbohydrates Dithiocarbonic Acid Esters and Their Application in Glycosylation Reactions

80%

Ślusarczyk A. , Sieroń A. , Szeja W.

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2001

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tom Vol. 75, nr 1

49-54

EN

Allyl dithiocarbonic acid esters are used as efficient glycosyl donors in the presence of soft activators. Different glycosides are obtained in good yields, isomer alfa being the main product.

3

Streospecific synthesis of A glycosides and A disaccharides of ulosonic acids via direct addition of alcohols to sugar ketene dithioacetal

80%

Młynarski J. , Banaszek A.

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1999

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tom vol. 73 nr 6

973-979

EN

A new direct route to the stereospecific construction of a glycosides and a disaccharides of ulosonic acids is presented. Addition reaction of alcohols and/or "sugar alcohols" to the quaternary double bond of sugar ketene dithioacetal 1 mediated by trimethylsilyl triflate led to the corresponding O-glycosides. Subsequent hydrolysis of dithianyl residue afforded the title compounds.

4

Stereoselective Synthesis of Alkyl alfa-D-Glucopyranosides

80%

Kasprzycka A. , Pastuch G. , Cyganek A. , Szeja W.

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tom Vol. 77 / nr 2

197-201

EN

Glycosylation of _-D-glucosyl N-allyl thiocarbamates with alcohols using bromine as activator proceeded under mild conditions in a highly stereoselective fashion to afford the corresponding _-glucosides in high yields. Hindered tertiary alcohols can be also used as glycosyl donors.

5

Glukozynolany - znaczenie i metody oznaczania

51%

Bartoszek A. , Kusznierewicz B. , Piasek A. , Śmiechowska A. , Namieśnik J.

Analityka : nauka i praktyka

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2009

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tom nr 3

16-21

PL

W ostatnim czasie ogromne zainteresowanie budzą bioaktywne fitozwiązki występujące w roślinacha jadalnych. Wśród prozdrowotnych fitozwiązków szczególne miejsce zajmują glukozylany.

6

ESI-ion trap multistage and MALDI-TOF mass spectrometry study of protonated per-O-acetyl indole glucosides

41%

Bekesova S. , Cmelik R. , Humenik M. , Kutschy P. , Kovacik V.

Chemia Analityczna

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2005

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tom Vol. 50, No. 1

223-233

EN

Structure of the title compounds -synthetic precursors of phytoalexin analogs- includes per-O-acetylated D-glucose and N-pheny! substituted indole carboxamide or carbothioamide moieties. Fragmentation mechanisms of these compounds have been studied by electrospray (ESI) ion trap (IT) multistage (MSn=1-5) mass spectrometry and matrix assisted laser desorption/ionization time-of-flight (M ALDT-TOF) techniques. In the primary ionization process, per-O-acetylated indole glucoside cationized (H. Na and K) adducts have been observed. Three fragmentation pathways of the protonated molecules are described. Two of the routes are dominated by the cleavage of the saccharidic part, while in the third one the cleavage of aglycons is a predominant process. Fragmentation of the carbonyl group differs from that of the thiocarbonyl analog. The influence of electron-donating or electron-accepting groups of the aromatic ring on the fragmentation pathways is also discussed. The presented theoretical data on the ESI and MALDI behavior of the saccharidic as well as of the indole and phenyl aglycon parts can facilitate structure elucidation of the analogous compounds.

PL

Elementami struktury tytułowych glukozydów - syntetycznych prekursorów analogów • fitoaleksyny - są N-fenylo podstawione karhoksoamidy lub karbotioamidy indolu i per-O-acelylowana D-glukoza. Fragmentację tych związków badano stosując wielostopniowa (MSn, n= 1-5) spektrometrię mas z jonizacją przez elektro rozpylanie oraz spektrometrię mas czasu przelotu z jonizacją przez desorpcję laserową z udziałem matrycy. W pierwszym procesie jonizacji obserwowano kationowane (H, Na, K) addukty glukozydu per-O-acetyl indolu. Opisano trzy drogi frakcjonowania protonowanych cząsteczek. Dwie z nich są zdominowane przez rozszczepienie części sacharydowej. w trzeciej dominuje rozszczepienie części aglikonowej. Fragmentacja grup karbony Iowy cli różni się od fragmenlac j i analogów tiokarbonylowych. Przedyskutowano wpływ grup elektrono-donorowych i elek-trono-akceptorowych w pierścieniu aromatycznym na drogi fragmentacji. Przedstawione teoretyczne dane, dotyczące zachowania się w ESI i MALDI części sacharydowej i części aglikonu indolowego i fenylowego, ułatwiają wyjaśnienie struktury analogicznych związków.

7

Saponiny steroidowe

41%

Myszka H. , Bednarczyk D.

Wiadomości Chemiczne

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2005

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tom [Z] 59, 3-4

275--303

EN

Chemistry and biochemistry of glycoconjugates have been a serious challenge for scientists since many years. Among the huge number of glycoconjugates there is a large group of compounds called saponins, specific glycosides that can be found in many plants. However, they can also be collected from some marine organisms. Nowadays, the main source of saponins is the flora of tropical and temperate zones, such a kind of plants: Costus, Discorea, Paris, Solanum, Trigonella, Trillium and Yucca. Furthermore, the large quantities of saponin can be found in food and beverage plants, including oats, peanuts, soybeans, garlic, onion, spinach, leafs of tea, etc. They are active components of some herbs used in therapeutics, e.g. in Poland the fenugreek seeds are used as a decoction for treatment of skin inflammation, moreover they are the components of antisnoring drops, as well as a part of nutrients for culturists. In Orient countries the number of saponins have long been used as pharmaceutical agents, such as those from ginseng, red clover, licorice, horse chestnut, senega and from many others traditional Chinese herbal medicinal plants. The popularity of the discussed group of glycosides comes from their interesting bioactivity. Biological investigations showed that saponins stop the sedimentation process of lipids on the aorta-wall, they slow down the production of sugars, proteins, lipids and bile acids in the liver. Furthermore, they are good antifungal and antibacterial agents, also show an anti-inflammatory and antiallergic activity. It has been found that the crude extract of some plants, especially in the aerial portion, containing the diosgenin glycosides display anti-neoplastic properties against several strains of human cancer cells. Structurally, the saponins are classified as steroid or triterpenoid glycosides depending upon the nature of the aglycone, which is generally called sapogenin. The steroid saponins have cyclopentaphenantrene backbone in aglycone, for example diosgenin, tigogenin, sarsapogenin. Saponins containing nitrogen in aglycone backbone belong also to this group. Triterpenoid saponins have usually 30-carbon atoms in tetra- or pentacyclic aglycone. The carbohydrate residue (hydrophilic part of glycosides), usually a mono-, di-, tri- or tetrasaccharide, is covalently attached to the sapogenin backbone (hydrophobic element). The sugar moiety, in most saponins, is attached to the 3-OH of a sapogenin via the 1,2-trans-glycosidic bond. The difficulties in isolation of homogeneous saponins from natural sources prompted chemists to the synthesis of these type compounds. Chemical synthesis could provide a real way to the availability of required saponins. The largest and also the most interesting class of saponins is the first group - the steroid saponins, because of their biological activity. To this group belong three class of compounds: cholestanoic, furostanoic and spirostanoic saponins.