Anomeric specificity of D-glucose metabolism study in rat and human erythrocytes

The anomeric specificity of D-glucose metabolism in erythrocytes has been since 1985 the matter of extensive investigations reported in about ten publications. The present report aims at providing an integrated review of the major findings on this issue.

Anomeric Proton and Carbon (H1-C1) NMR Chemical Shifts of Antigenic Mannans Obtained from Pathogenic Yeast <i>Candida tropicalis</i>

On two dimensional maps of 1H-13C correlation spectroscopy (H-C COSY) analysis for the mannan of Candida tropicalis, nine cross peaks of anomeric proton and carbon were useful for the purpose of obtaining information on the chemical structure of this molecule. Namely, the mannans was comb-like structure constructed with the linear α-1,6-linked polymannnosyl backbone and several oligomannnosyl side chains composed of α-1,2-, α-1,3-, and β-1,2-linkages. Therefore, in the structural investigation of comb-like mannan, two-dimensional H-C COSY analysis is as useful as two-dimensional nuclear Hartmann-Hahn (HOHAHA) analysis.

An Anomeric Base-Tolerant Ester of 8-Alkynyl-1-naphthoate for Gold(I)-Catalyzed Glycosylation Reaction

Given the extreme complexity and diversity of carbohydrates,efficient approaches to the homogeneous oligosaccharide remain limited.Chemical synthesis represents one of the most reliable methods to access homogeneous samples,which mainly relies on the key glycosylation reaction.Consistent with enormous efforts to develop leaving groups for establishing robust glycosylation protocols,we herein disclose a structurally novel leaving group of 8-phenylethynyl-1-naphthoate that is able to enable efficient glycosylation reactions under the extremely mild condition of gold(I)-catalysis.Notably,the anomeric naphthoate possesses the unprecedent character of base-stability in sharp contrast to the conventional ester groups at anomeric position of carbohydrates,which endows high compatibility with a variety of chemical transformations.Furthermore,the present glycosylation protocol with 8-phenylethynyl-1-naphthoate as leaving group is able to realize minimally protected glycosylation processes.Mechanistic studies reveal a unique structure of 8-phenylethynyl-1-naphthoate that accounts for the reason for these characteristics.

Anomeric configuration-dependence of the Lattrell-Dax epimerization from D-glucose to synthetically useful D-allose derivatives

D-Allose and its derivatives play important roles in the field of health care and food nutrition. Pure and well-defined Dallose derivatives can facilitate the elucidation of their structure-activity relationship as an essential step for drug design. The LattrellDax epimerization, refers to the triflate inversion using nitrite reagent, is known as valuable method for the synthesis of rare D-allose derivatives. Here, the influence of protecting group patterns on the transformation efficiency of D-glucose derivatives into synthetically useful D-alloses and D-allosamines via the Lattrell-Dax epimerization was studied. For C3 epimerization of D-glucose derivatives bearing O2-acyl group, an anomeric configuration-dependent acyl migration from O2 to O3 was found. In addition, a neighbouring group participation effect-mediated SN1 nucleophilic substitution of the D-glucosamine bearing C2 trichloroacetamido(TCA) group in the Lattrell-Dax epimerization was dependent upon anomeric configuration. Thus, the effect of anomeric configuration on the LattrellDax epimerization of D-glucose suggests that β-D-glucosides with low steric hindrance at C2 should be better substrates for the synthesis of D-allose derivatives. Significantly, the efficient synthesis of the orthogonally protected D-allose 13 and D-allosamine 18 will serve well for further assembly of complex glycans.

Highly Stereoselective C-Glycosylation by Photocatalytic Decarboxylative Alkynylation on Anomeric Position:A Facile Access to Alkynyl C-Glycosides

The highly stereoselective synthesis of diverse medicinally valuable alkynyl C-glycosides under mild and green reaction conditions remains a great challenge.Herein,we wish to report a visible-light induced photocatalytic decarboxylative alkynylation approach.By utilizing an iridium photocatalyst in the presence of visible light,glycosyl radicals are in-situ generated via the decarboxylation of anomeric acids and efficiently coupled with a variety of ethynylbenziodoxolones(EBXs),which allows the facile synthesis of a variety of alkynyl C-glycosides in moderate to high yields and with excellent diastereoselectivity.

An Alternative Method for Anomeric Deacetylation of Per-acetylated Carbohydrates

An alternative method for anomeric deacetylation of fully acetylated carbohydrates has been developed using imidazole in methanol.

Terahertz Time-Domain Spectroscopy to Identify and Evaluate Anomer in Lactose

Lactose powder consisting of α-D-lactose monohydrate and anhydrous β-D-lactose was nondestructively and quantitatively evaluated by transmission-type Terahertz time-domain spectroscopy (THz-TDS). An absorption with peak at 39.7 cm-1 (1.19 THz) was assigned to be derived from anhydrous β-D-lactose, in addition to the absorptions due to α-D-lactose monohydrate with peak at 17.1 cm-1 (0.53 THz) and 45.6 cm-1 (1.37 THz). After deconvolution of the spectra using Lorentzian, integrated intensities of the absorptions with peak at 39.7 cm-1 and 45.6 cm-1 were uniquely dependent on the weight composition ratio of the α-and β-lactose powder. As a result, the net molar-ratio of the α-and β-lactose in lactose powder could be precisely evaluated by the integrated intensity ratio. Further, anomer content in lactose powder extracted from lactose solution was evaluated and the refined and unrefined features were shown by the evaluation method.

THE VIRTUAL LONG-RANGE COUPLING IN THE ~1HNMR SPECTRA OF 1-O-ACYL-TETRA-O-ACETYL-β-D-HEXAPYRANOSE

Since the study of the nuclear magnetic resonance （NMR）spectra of a number of sixmembered ring compounds reported by Lemieux et al. in 1958, the chemical shift and coupling constant for H1 have been used extensively to identify anomeric isomers in carbohydrate compounds. In 1-O-acyl-tetra-O-acetyl-β-O-hexapyranose, the anomeric proton of the

An efficient and facile approach for the construction of chondroitin sulfate E oligosaccharide precursors

An efficient and facile approach has been developed for the construction of chondroitin sulfate E(CS-E)oligosaccharide precursors. In this approach, the disaccharide unit with the GalNAc-GIcA sequence was first elongated to form tetra-and hexasaccharides followed by the introduction of anomeric groups via glycosylation couplings. A number of CS-E tetra-and hexasaccharide precursors were prepared in high yields.

Stereoselectivity of Acetalization and Ketalization Reactions of Glycerol and Its Modified Derivatives

Twenty one 1,3 dioxolanes with varieties of substituents at 2,4 positions were synthesized by acid catalyzed acetalization and ketalization reactions of glycerol and its modified derivatives. The assignment and quantitative analyses of thermodynamically equilibrated cis and trans 1,3 dioxolanes were completed by 1H NMR. The stereoselective regularity was found in acetalization and ketalization reactions of glycerol and its modified derivatives. The stereoselective regularity of the condensation reactions was reasonably explained by anomeric effect and 2,4 nonbonded interaction.