In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-β-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain β-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of β-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in β-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.
Glycosides ; Mannosides ; Glycosylation ; Stereoisomerism

AIMTo study the bioactive constituents from the flower of Castanea mollissima Blume.

METHODSCompounds were isolated and purified by column chromatography on silica gel and polyamide. Structures were determined by various spectroscopic data,including UV, IR, 1H and 13CNMR, EIMS and FABMS, 1H-13C-COSY and HMBC.

RESULTSTwo compounds were isolated from the ethyl acetate fraction of 95% ethanol extract and the structures were elucidated as kaempferol-3-O-[6"-(E)-p-coumaroyl]-alpha-D-mannopyranoside (1) and kaempferol-3-O-[6", 4"-di-(E)-p-coumaroyl]-alpha-D-mannopyranoside (2).

CONCLUSIONCompounds 1 and 2 are new compounds, named castanoside A and B respectirely.

Fagaceae ; chemistry ; Flowers ; chemistry ; Glucosides ; chemistry ; isolation & purification ; Kaempferols ; chemistry ; isolation & purification ; Mannosides ; chemistry ; isolation & purification ; Molecular Conformation ; Molecular Structure ; Plants, Medicinal ; chemistry

OBJECTIVETo study the chemical constituents in the Galeobdolon chinense.

METHODThe chemical constituents were separated by means of chromatogrophy, and their structures were identified by spectra of FAB-MS, IR, UV, 1H-NMR, 13C-NMR, DEPT, HMQC and HMBC.

RESULTTwo compounds were obtained and identified as galeobdoside (I) whose structure was apigenin-7-O-beta-D-(6'-p-hydoxy-cinnamoyloxy)-mannoside and verbascoside (II).

CONCLUSIONCompound I was a new compound and compound II was obtained from this plant for the first time.

Flavonoids ; chemistry ; isolation & purification ; Glucosides ; chemistry ; isolation & purification ; Lamiaceae ; chemistry ; Mannosides ; chemistry ; isolation & purification ; Molecular Conformation ; Molecular Structure ; Phenols ; chemistry ; isolation & purification ; Plants, Medicinal ; chemistry

AIMTo study the biotransformation of kaempferitrin, a major chemical principle of the fruits of Siraitia grosvenori (Swingle) C. Jeffery, with human intestinal flora.

METHODSThe kaempferitrin was incubated with human intestinal flora. The biotransformation products were isolated and purified by chromatographic methods and the structures were determined by spectroscopic techniques.

RESULTSKaempferitrin was converted into kaempferol 3-O-alpha-L-rhamnoside (afzelin, I) , kaempferol 7-O-alpha-L-rhamnoside (II), kaempferol (III) and p-hydroxybenzoic acid (IV) by human intestinal flora. rhamnoside (II), kaempferol (III) and p-hydroxybenzoic acid (IV) by human intestinal flora.

CONCLUSIONThe structure of kaempferitrin can be biotransformatedly converted by human intestinal flora.

Bacteria ; metabolism ; Biotransformation ; Fruit ; chemistry ; Humans ; Intestines ; microbiology ; Kaempferols ; isolation & purification ; metabolism ; pharmacokinetics ; Mannosides ; metabolism ; Momordica ; chemistry ; Parabens ; metabolism ; Plants, Medicinal ; chemistry ; Proanthocyanidins ; metabolism

This report describes surface properties of several cell membranes tested by lectininduced agglutination reactions which were quantitated using the microquantitative particle counter agglutination assay of Davis et al. (1976). The quantitative assays of concanavaalin A (con A) induced agglutination were performed for rabbit erythrocyte, rat erythrocyte, human erythrocyte, and sarcoma 180 mouse ascites cells. The percent agglutination versus the con A concentration revealed a sigmoid curve in all cases, but the steepness of the sigmoid curve is variable depending on the cell types. It varies even with the same cell but in different species. Optimum cell concentration was (0.92-0.95) x 10(7) cells/ml final concentration in the hanging drop, for rabbit erythrocytes, (0.77-1.64) x 10(7) cells/ml for rat erythrocytes, (1.59-2.7) x 10(7) cells/ml for human erythrocytes and (0.23-0.39) x 10(7) cells/ml for sarcoma 180 mouse ascites cells. When minimal and maximal agglutination percentages were defined as the concentration of con A/ml/1 x 10(6) cells corresponding to 10% and 95% agglutination, minimal and maximal agglutination occured at 0.56 ug, 19.98 ug for human erythrocytes at 0.56 ug, 224 ug for rat erythrocytes at 0.08 ug, 1.43ug for rabbit erythrocytes at 0.12 ug, 14.8 ug for sarcoma 180-mouse ascites cells respectively. The order of inhibitory activity of alpha-methyl-D-mannopyranoside (alphaMM) for each corresponding cells from the highest inhibition was human erythrocytes, rat erythrocytes, sarcoma 180 mouse ascites cells and rabbit erythrocytes. The concentrations of alphaMM required for 50% inhibition per ml of the final concentration in the hanging drop per 1 x 10(7) cells were 0.565 umoles for rabbit erythrocytes, 0.072 umoles for rat erythrocytes, 0.018 umoles for human erythrocytes and 3.677 umoles for sarcoma 180 mouse ascites cells, respectively. From our experimental results we conclude that the cytoagglutination activity was increased with con A, the inhibitory activity with alphaMM in the presence of con A was decreased, however the sarcoma 180 mouse ascites cells revealed a contradictory result, and might be due to the topological distribution of agglutination site changes to a distribution more favorable for agglutination.
Agglutination ; Agglutination Tests ; Animal ; Cell Membrane/immunology* ; Concanavalin A/pharmacology* ; Erythrocytes/immunology ; Human ; Methylmannosides/pharmacology ; Mice ; Rabbits ; Rats ; Sarcoma 180/immunology ; Surface Properties