Wyniki wyszukiwania - BazTech

1

Naturalne i syntetyczne niecukrowe substancje słodkie

Uher M., Wójtowicz H.

Wiadomości Chemiczne

|

2003

|

[Z] 57, 5-6

505--546

EN

Sweet tasting food-stuffs have been always, in all probability, an integral part of human diet. This problem concentrate scientific interest of dietetics but also chemists and biologists. In the article actual knowledge on the natural and synthetic non-saccharide sweeteners is reviewed. The sweeteners presented here are divided, depending of their origins, on the compounds isolated from natural sources and compounds synthesized from simple organic precursors. One of the most important groups of naturally devided sweeteners are peptides. Some of them, particularly thaumatins find practical application as additives to a tooth-paste, food, drinks and drugs. The majority of intensely sweet naturally occurring compounds belong to the family of terpenoids comprise monoterpenoids, sesquiterpenoids as well as di- and triterpenoids. Their most prominent representatives such as perillartine, stevioside and glycyrrhizin are presented more detaily. Other groups of sweet tasting naturally occurring substances, mentioned in this paper are steroidal saponins, dihydroisocumarins, flavanoids and related compounds and less common species such as haematoxylin, telosmosides and monatin. The second part of the article is devoted to synthetic sweeteners. The well known representatives such as saccharin, cyclamates, Acesulfame-K, aspartame, alitame, neotame and sucralose are presented more detaily and methods of their synthesis are briefly reported. Organoleptic properties of the most compounds are characterized and related to the molecular structure of sweetener is discussed. New trends and perspectives of application non-saccharide sweeteners are formulated.

2

Hyrdoperoxide Oxidation of Azomethines and Alkylarenes Catalyzed by Ebselen

Giurg M., Wójtowicz H., J. Młochowski J.

Polish Journal of Chemistry

|

2002

|

Vol. 76 / nr 4

537-542

EN

2-Phenyl-1,2-benzisoselenazol-3(2H)-one (ebselen), known as glutathione peroxidase mimic, is found as an efficient catalyst for hydrogen peroxide and tert-butyl hydroperoxide oxidation of the azomethine group in azines, aldoximes, and methyl or methylene group in alkylarenes. Depending on the substrate used and the reaction conditions, the major products are aldehydes, ketones, carboxylic acids or their derivatives. It is postulated that ebselen is involved in the free-radical oxidation mechanism.

3

Związki selenu jako odczynniki i katalizatory w reakcjach utleniania związków organicznych

Młochowski J., Brząszcz M., Giurg M., Wójtowicz H.

Wiadomości Chemiczne

|

2001

|

[Z] 55, 1-2

9--44

EN

Oxidation reactions are fundamental processes widely applied in organic synthesis. Among many reagents used in these reactions, elemental selenium and particularly some of its compounds have been reported as effective and selective oxidants and catalysts for the oxidation of various organic substrates. One of them is selenium(IV) oxide, easily available regent for hydroxylation of activated a-positions particularly at allylic and propargylic sites. It also can introduce carbonyl functionality at activated positions. Used in combination with hydrogen peroxide or t-butylhydroperoxide it acts as oxygen-transfer agent. Both of these hydroperoxides can be used in the presence of selenium(IV) oxide for epoxidation, 1,2-dihydroxylation and a-carbonylation of alkenes, for oxidation of aldehydes into carboxylic acids, sulfides to sulfoxides or sulfones, secondary amines to nitrones and for other reactions. Benzeneseleninic acid, other areneseleninic acids and their anhydrides are known as stoichiometric oxidants or activators of other oxygen donors. They have been successfully applied for oxidation of many organic compouns, among them alkenes, alcohols, phenols, amines, hydrazones, sulfides, 1,3-dithiolanes and azines. Organic diselenides, the precursors of seleninic acids, have been used as oxygen-transfer catalysts for oxidation of various functional groups with hydrogen peroxide, t-butylhydroperoxide and other oxygen donors , while dimethyl and diphenyl selenoxides are efficient stoichiometric oxidants (e.g. for conversion of halomethyl or hydroxymethyl group into formyl group]. Most recently, selenenamides, particularly 2-phenyl-1,2-benzisoselenazol-3(2H)-one (ebselen) and its analogous were found as efficient catalysts for hydrogen peroxide and tbutylhydroperoxide oxofunctionalization of olefins, oxidation of azomethine compounds and sulfides.