Synthesis of ketopyranosyl glycosides and determination of their anomeric configuration on the basis of the three-bond carbon-proton couplings

Anomeric pairs of ketopyranosyl glycosides with various substituents at C(alpha), C(beta) and C(gamma) were synthesized from the corresponding thioglycosides, and the influence of the C(alpha)-C(beta)-C(gamma)-H(gamma) torsion angle and substituent effects on the three-bond carbon-proton couplings was studied. The cis coupling constants range from 1 to 2Hz. The trans couplings are generally as small as 2.3-2.6Hz; however, for compounds bearing an unsubstituted gamma-carbon, a relatively large trans coupling was measured (4.8Hz). An S-ethyl group at the beta-position increases the cis coupling (up to 3.2Hz) compared to the corresponding O-glycosides.     

Interaction of metal ions with D-glucobenzothiazoline: isolation and characterization of the resultant products

Six different metal-ion complexes of D-glucobenzothiazoline were synthesized and characterized by analytical and spectral techniques. Formation of different types of species (ML and ML(2)) were observed with Cu(2+), Ag(+), Cd(2+), Hg(2+), and Zn(2+) ions. Existence of an anomeric mixture in the case of the Cu(2+) complex is identified from the EPR spectra, and the results were further supported by the simulated spectra. The structures were proposed based on different studies.     

Synthesis of a set of sulfated and/or phosphorylated oligosaccharide derivatives from the carbohydrate-protein linkage region of proteoglycans

The synthesis of a set of various sulfoforms and/or phosphoforms as 7-methoxy-2-naphthyl glycosides of beta-D-Xylp, beta-D-Galp-(1-->4)-beta-D-Xylp, and beta-D-Galp-(1-->3)-beta-D-Galp-(1-->4)-beta-D-Xylp, structures encountered in the common carbohydrate-protein linkage region of proteoglycans, is reported for the first time. These molecules will serve as probes for systematic studies of the substrate specificity of the glycosyltransferases involved in the early steps of the biosynthesis of proteoglycans. A straightforward divergent preparation was achieved using key intermediates, which were designed as common precursors.     

Synthesis of novel siRNAs having thymidine dimers consisting of a carbamate or a urea linkage at their 3' overhang regions and their ability to suppress human RNase L protein expression

In order to examine the effect of modifications at the 3' overhang regions of short interfering RNAs (siRNAs) on their gene-silencing activities, we designed and synthesized novel siRNAs having thymidine dimers consisting of a carbamate or a urea linkage at their 3' overhang regions. Suppression of human RNase L protein expression by these siRNAs was analyzed by immunoblot with RNase L-specific antibody. It was found that, at 24 h post-transfection, the modified siRNAs having the thymidine dimers with the carbamate and urea linkage suppress the protein expression 78 and 37 times more efficiently than that with the natural phosphodiester linkage, respectively. Furthermore, the siRNA containing the carbamate linkage was 37 times more resistant to nucleolytic degradation by snake venom phosphodiesterase than the siRNA consisting of the natural phosphodiester linkage. Thus, the RNA duplexes having the thymidine dimers with the carbamate or urea linkage at their 3' overhang regions will be promising candidates for novel siRNA molecules to down-regulate protein expression.