Yeşim Salman

Tricyclic ortho ester formation from trichloroethylidene acetals of sugars via ketene acetals

Abstract One step formation of the tricyclic dichloroethylidyne ortho esters from the reaction of trichloroethylidene acetals of D-galactose and D-arabinose with K tert-butoxide are described. The possible intermediate, i.e, ketene acetal was prepared separately, from the suitably protected 1,2-O-trichloroethylidene-α-D-galactofuranose. Stereoselective formation of an ortho ester anhydride, from the ketene acetal is also described.

Synthesis of novel Schiff base ligands from gluco- and galactochloraloses for the Cu(II) catalyzed asymmetric Henry reaction.

A series of chiral Schiff base ligands has been prepared using aminochloralose derivatives of glucose and galactose. These ligands were used as catalysts in the asymmetric Henry reaction in the presence of Cu(II) ions giving yields of up to 95%. An interesting solvent dependency on enantiomeric control was observed with the best enantiomeric excesses (up to 91%) being obtained in the presence of water.

Acid promoted intramolecular formation of 3,5-anhydro-1,4-furano-7-ulose derivatives via the Wittig-cyclization procedure and their antimicrobial properties

We report a convenient method for the synthesis of 3,5-anhydrofuranose derivatives. Formation of the 3,5-anhydro (oxetane) rings was achieved by the Wittig-cyclization procedure under acid promoted conditions starting from 5(E)-eno-1,4-furano-7-ulose derivatives (1, 4, and 7). Unprotected hydroxyl groups on C-3 of the furanose rings added intramolecularly to the acyclic double bond under very mild acidic conditions in methanol to form the stereoisomeric 3,5-anhydro derivatives in good yields. The products (2, 3, 5, 6, and 8) were found to exhibit antibacterial properties. The reaction was found to be strongly solvent dependent as use of methanol instead of chloroform afforded 5-acetylmethyl-furfural 9 as a major product instead of the expected oxetane. All of the synthesized compounds were tested for antimicrobial activity against Staphylococcus aureus ATCC6538-P, Bacillus subtilis ATCC 6633, Salmonella typhimurium CCM 5445, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 12228, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae CCM 2318, and Candida albicans ATCC 10239 and exhibited a range of activities against selected microorganisms.

Novel glyconanoconjugates: synthesis, characterization and bioapplications

The impressive properties of nanoparticles (NPs) have caused them to gain considerable attention for biological applications such as cancer therapy. Among the many nanoparticles used in the treatment of cancer, carbohydrate derivatized modified NPs lead the way with enhanced internalization and therapy efficacy for cancerous cell lines. In this research, an aminochlorase Schiff base, which can be beneficial as a therapy material, with a galactose residue was used as a potentially active modifier. Gold and silver nanoparticles (AuNPs and AgNPs) can be readily modified with a sugar Schiff base ligand (1) by using cysteamine hydrochloride residues as a linker between the nanoparticle surface and the ligand. The resulting glyco-nanoparticles were characterized using transmission electron microscopy, X-ray photoelectron microscopy and spectrophotometric techniques. Additionally, this modification type within a galactose derived Schiff base is the first work with a bioapplication, especially in radiotherapy. For further biological applications in cancerous cell lines, two commonly used cell lines, human cervix adenocarcinoma (HeLa) and human lung carcinoma cell line (A549) were introduced into the biological evaluation of those NP–ligand conjugates and satisfactory radioactivity results were obtained because of the radiosensitizing effect of the AuNPs and AgNPs.

A Convenient Synthesis of a Cardiac Sugar: “D-Digitalose”

D-Digitalose (6-deoxy-3-O-methyl-D-galactose), a biologically important sugar that is found in some cardiac glycosides, was synthesized from D-galactose via 3-O-methyl-1,2,5-O-orthodichloroacetyl-α-D-galactofuranose.

DNA isolation by galactoacrylate-based nano-poly(HEMA-co-Gal-OPA) nanopolymers

Abstract Isolation of DNA is one of the important processes for biotechnological applications such as investigation of DNA structures and functions, recombinant DNA preparations, identification of genetic factors and diagnosis and treatment of genetic disorders. The aim of this study was to synthesis and characterizes the galactoacrylate based nanopolymers with high surface area and to investigate the usability of these synthesized nanopolymers for DNA isolation studies. Nanopolymers were synthesized by the surfactant free emulsion polymerization technique by using the monomers of 2-hydroxyl ethylmethacrylate and 6-O-(2′-hydroxy-3′-acryloyloxypropyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. Galactoacrylate origin of these newly synthesized nanopolymers increased the interaction between DNA and nanopolymers. Prepared nanopolymers were characterized by SEM, FT-IR and ZETA sizer analysis. Synthesized nanopolymers were spherical, and their average particle size was about 246.8 nm. Adsorption of DNA onto galactoacrylate based nanopolymers was investigated by using different pHs, temperatures, ionic strength, DNA concentrations and desorption studies and maximum DNA adsorption was found to be as 567.12 mg/g polymer at 25 °C, in pH 5.0 acetate buffer. Reusability was investigated for 5 successive reuse and DNA adsorption capacity decreased only about 10% at the end of the 5th reuse.

Synthesis, Characterization, and Thermokinetic Analysis of New Epoxy Sugar Derivative

The synthesis of 5,6-O-isopropylidene-1,2-O-(R)-trichloroethylidene-α-D-glucofuranose (compound 1) and 5,6-O-isopropylidene-1,2-O-(R)-trichloroethylidene-3-O-(2′,3′-epoxypropan-1′-yl)-α-D-glucofuranose (compound 2) was carried out. The synthesized compounds 1 and 2 were characterized by nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TG). The FTIR and 1H NMR spectra showed that the epoxy group in compound 2 was attached by means of a nucleophilic substitution reaction. The activation energies for thermal degradation of compounds 1 and 2 were calculated from their TG data by using the Kissinger-Akahira-Sunose (KAS) and Tang methods.

Mannose based polymeric nanoparticles for lectin separation

ABSTRACT The aim of this work is to synthesize the original, new polymeric nanoparticles for concanavalin A (Con A) purification. Nanoparticles were synthesized by surfactant free emulsion polymerization. In the polymerization prosedure, 1-O-(2′-hydroxy-3′-acryloyloxypropyl)-2,3:5,6-di-O-isopropylidene-α-D-mannofuranose (Man-OPA) was used as co-monomer and 2-hydroxyethylmethacrylate (HEMA) was used as a monomer. Man-OPA was characterized by Fourier Transform Infrared Spectroscopy (FTIR), nuclear magnetic resonance and elemental analysis techniques. Poly(HEMA-Man-OPA) nanoparticles were characterized by scanning electron microscopy, FTIR and Zeta Sizer. In adsorption‒desorption experiments, maximum Con A adsorption capacity of poly(HEMA-Man-OPA) nanoparticles was found 630.6 mg/g nanoparticle (pH 7.5, 1.0 mg/mL). Adsorption‒desorption experiments were repeated in four times. According to results, these nanoparticles could be used several times without significant decrease in Con A adsorption capacity.