Bucharest, Romania
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Iga D.P.,Faculty for Biology | Iga S.,Faculty for Biology | Velicu N.,Spiru Haret University | Petrut T.,Spiru Haret University | Condur N.-D.,Spiru Haret University
Romanian Biotechnological Letters | Year: 2010

Glycosylation of 4-nitrocatechol with tetra-O-acetyl α-D-galactofuranosyl bromide, by different methods (Koenigs-Knorr, Helferich, reaction with phenoxide) led to 4'-nitrocatechol 1'-yl β-D-(2,3,5,6-tetra-O-acetyl)galactofuranoside. Glycosylation donor, tetra-O-acetyl α-D-galactofuranosyl bromide, was obtained by bromination of penta-O-acetyl β-D-galactofuranose with hydrogen bromide in glacial acetic acid. β-D-Galactofuranose pentaacetate was synthesized by peracetylation of D-galactose in boiling pyridine followed by separation of the aimed product by fractional crystallization. The crystalline mass obtained was recrystallized from ethanol. Due to the fact that penta-O-acetyl β-D-galactofuranose has levorotary action, optical rotation was a constant guide along the preparation of the furanosic precursor. The aglycon, 4-nitrocatechol, was prepared by acidic hydrolysis of 2-hydroxy 5-nitrophenyl sulfate, synthesized at its turn by reacting 4-nitrophenol and potassium persulfate in a strongly alkaline environment conferred by potassium hydroxide. All intermediates and products were characterized chemically and by physical methods. © 2010 University of Bucharest.


Iga S.,Faculty for Biology | Iga D.P.,Faculty for Biology | Nicolescu A.,Petru Poni Institute of Macromolecular Chemistry | Florentina D.,Spitalul Clinic de Urgenta Floreasca | Cimpeanu G.,Faculty for Biotechnology
Romanian Biotechnological Letters | Year: 2011

Two complementary methods for the preparation of ceramide and sphingosine have been elaborated. (i) Galacto- or glucocerebrosides were oxidized with periodate and the newly formed aldehyde groups were reduced to alcohols by reaction with NaBH 4. By this treatment, susceptibility of sugar cleavage residues to acidic hydrolysis was increased, so they were removed by mild acidic hydrolysis. The product of this ensemble of reactions was ceramide but it could be converted to sphingosine by a stronger acidic hydrolysis. (ii) Sphingolipids (sphingomyelin, glucocerebrosides, galactocerebrosides), isolated from adequate sources, were cleaved to their chemical constituents by an energetic acidic hydrolysis. From this mixture, sphingosine was isolated by partition and column chromatography, and N-acylated with the choice fatty acid. Finally, both ceramides and sphingosine were analyzed by chemical and physical methods (IR, NMR) per se or in peracetylated form. The implications of a mathematical equation describing molecular diversity of ceramides, in connection with their biochemical transformations, has been also discussed. © 2011 University of Bucharest.


Iga S.,Faculty for Biology | Iga D.P.,Faculty for Biology | Nicolescu A.,Petru Poni Institute of Macromolecular Chemistry | Florentina D.,Spitalul Clinic de Urgenta Floreasca | And 2 more authors.
Romanian Biotechnological Letters | Year: 2011

Two complementary methods for the preparation of ceramide and sphingosine have been elaborated. (i) Galacto- or glucocerebrosides were oxidized with periodate and the newly formed aldehyde groups were reduced to alcohols by reaction with NaBH4. By this treatment, susceptibility of sugar cleavage residues to acidic hydrolysis was increased, so they were removed by mild acidic hydrolysis. The product of this ensemble of reactions was ceramide but it could be converted to sphingosine by a stronger acidic hydrolysis. (ii) Sphingolipids (sphingomyelin, glucocerebrosides, galactocerebrosides), isolated from adequate sources, were cleaved to their chemical constituents by an energetic acidic hydrolysis. From this mixture, sphingosine was isolated by partition and column chromatography, and N-acylated with the choice fatty acid. Finally, both ceramides and sphingosine were analysed by chemical and physical methods (IR, NMR) per se or in peracetylated form. The implications of a mathematical equation describing molecular diversity of ceramides, in connection with their biochemical transformations has been also discussed. © 2011 University of Bucharest.


Iga D.P.,Faculty for Biology | Schmidt R.,University of Konstanz | Schmidt R.,King Abdulaziz University | Iga S.,Faculty for Biology | And 4 more authors.
Turkish Journal of Chemistry | Year: 2013

Glycosides of 4-nitrocatechol (1,2-dihydroxy 4-nitrobenzene) with a-D-glucopyranose and a-D-mannopyranose were synthesized by the glycosylation of phenol with peracetylated sugars in the presence of BF3.OBu2 . The glycoside of 4-nitrocatechol with β -D-galactopyranose was prepared by the glycosylation of this phenol as sodium phenoxide with tetra-O-benzoyl-a-D- galactopyranosyl bromide. The structure of the reaction products was confirmed by 1H and 13C NMR spectra and by chemical analysis. The latter consisted of acidic hydrolysis, followed by ethyl ether extraction and colorimetric determination of 4-nitrocatechol in the ether phase and application of the anthrone method for the sugar in the water phase. The synthetic glycosides were tested as substrates for enzymes from animal, vegetal, and microbial materials. © TÜBITAK.


Silvia I.G.A.,Faculty for Biology | Berechet D.,Romanian National Institute for Research and Development in for Textile and Leather | Adrian I.G.A.,Faculty for Biology | Predescu N.F.,LCCF Bucharest | Dumitru Petru I.G.A.,Faculty for Biology
Revista de Chimie | Year: 2010

D,L-α-Tocopherol was galactofuranosylated by boiling it for 7-8 h in dry toluene with tetra-O-benzoyl α-Dgalactofuranosyl bromide, cadmium carbonate as promoter and calcium sulfate as water scavenger. Reaction product was submitted to Zemplen saponification, and D,L- α-tocopheryl β-D-galactofuranoside was purified by column chromatography on silica gel and characterized by spectral (ESI-MS), chemical and chromatographical means. Contrary to this method of glycosylation, heating was avoided in the course of galactofuranosylation of thiamine (vitamin BI). In this sense, glycosylation was made by stirring a suspension consisting of thiamine, tetra-O-benzoyl α-D-galactofuranosyl bromide, calcium sulfate, cadmium carbonate and silver salicylate in dry toluene for 72 h at room temperature. Of reaction mixture, thiamine β-D-(2,3,5,6tetra-O-benzoyl) galactofuranoside was separated. Protecting groups were removed by Zemplen saponification and salinity was avoided by neutralization with Dowex 50W X8 (H+). Thiamine β-Dgalactofuranoside was characterized physico-chemically and chromatographically, and a small portion peracetylated and ESI-MS spectra registered.


Iga S.,Faculty for Biology | Iga A.,Faculty for Biology | Nicolescu A.,Petru PoniInstitute of Macromolecular Chemical | Iga D.P.,Faculty for Biology
Revista de Chimie | Year: 2010

A new synthesis of D,L-a-tocopheryl- a-D-mannopyranoside, an antiallergic and antiinflammatory compound, has been accomplished. The synthesis was based on the following steps: the monosaccharide was stirred in a mbcture of pyridine and acetic anhydride on an ice-water bath in order to obtain penta-O-aceyl-ß-Dmannopyranoside. The protected mannopyranoside was dried exhaustively in vacuum on phosphorus pentoxide, mixed with D, L- α-tocopher of, dried again, and then glycosylation method according to Helferich was accomplished. Toluene constituted the reaction environment and p-toluenesulfonic acid was glycosylation promotor. Reaction mixture was submitted to Zemplen saponification and then to column chromatography on silica gel. Two mannosides have been separated in the molar ratio 40:1, the minor one migrating faster by thin layer and column chromatography. Being characterized by their 1H and 13C NMR spectra as well as by chemical and chromatographical means, the major mannoside proved to be D,L-α- tocopheryl-cc-Dmannopyranoside and the minor one D,L-α-tocopheryl-ß- D-mannofuranoside. They both could constitute new possible metabolites of a-tocopherol and mannose, as well as new substrates for a-mannosidases.


Iga D.P.,Faculty for Biology | Iga S.,Faculty for Biology | Craciun A.,BIOMEDICAL
Romanian Biotechnological Letters | Year: 2010

The synthesis of the two glycoconjugates, DL- α-tocopheryl-α-D-mannopyranoside and -α-D-mannofuranoside, was based on the following steps: the penta-O-acetyl α-D-mannofuranose was synthesized via 1-O-n-octyl mannofuranoside and penta-O-acetyl α-D-mannopyranose by direct peracetylation of D-mannose in the cold. The two pentaacetyl mannoses were each one purified by repeated crystallization from ethanol and acetone and then dried exhaustively in vacuum on phosphorus pentoxide, mixed with DL-α-tocopherol, dried again, and then glycosylation method according to Helferich was accomplished. Toluene constituted the reaction environment and p-toluenesulfonic acid served as glycosylation promotor. Reaction mixture was submitted to Zemplen saponification and then to column chromatography on silica gel. The two glycoconjugates were characterized per se as well as after reacetylation. Being characterized by their 1H and,13C NMR spectra as well as by chemical and chromatographical means, they proved to be DL-α-tocopheryl-α-D-mannopyranoside and DL-α-tocopheryl-α-D-mannofuranoside, respectively. Both pyranosic and furanosic glycoconjugates could constitute new metabolites of α-tocopherol and D-mannose, as well as new substrates for exo-glycosidases. © 2010 University of Bucharest.

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