Journal of Carbohydrate Chemistry最新文献

The current body of research on the health implications of isoflavone phytoestrogens still presents unsolved matters pertaining to absorption, metabolism, and bioavailability. To conduct research in this particular domain, it is important to possess the means to obtain samples of both isoflavone 7-O-glucosides, which are naturally occurring in plants, and 7-O-glucuronides, which are major metabolites present in mammals. To comprehensively examine the potential health advantages, it is important to precisely measure the concentrations of phytoestrogens present in various food sources and bodily fluids. The use of C-labeled isoflavones was critical to the development of a methodology that allows for precise measurement. 2,3,4-¹³C-Labeled isoflavone 7-O-glucosides, namely 2,3,4-¹³C-labeled daidzin, genestin and glycitin, were efficiently prepared via BF₃·Et₂O catalyzed glycosylation at the 7-O-position of ¹³C-labeled 4′-O-hexanoyldaidzein, 4′-O-hexanoylglycitein and 5,4′-O-dihexannoylgenestein with 2,2,2-trifluoro-N-(p-methoxyphenyl)acetamidates as glycosyl donors. It was found that protecting all of the OH groups in the isoflavones with hexanoyl groups, with the exception of the 7-OH group, resulted in an increase in both their solubility in organic solvents and the reaction efficiency.

Gold-catalyzed glycosylation using alkyne donors is a versatile approach for the efficient assembly of diverse types of glycosides due to its catalytic and mild glycosylation properties. Minor structural alterations might significantly affect the glycosylation reaction when the alkyne-based leaving groups are simplified. By mapping the glycosylation reactivities of a series of structurally simplified alkyne donors, herein we demonstrate the role of each characteristic functional group of glycosyl ynenoates. Based on the isolation and the X-ray diffraction characterization of the pyran-5-ylgold(I) complex generated from the leaving group, a plausible mechanism of the gold(I)-catalyzed glycosylation with glycosyl ynenoates as donors was proposed.

Glycosylphosphatidylinositol (GPI) anchors contain a unique α-D-glucosamine-(1→6)-myo-inositol [αGlcN(1,6)Ins] motif in their conserved core structure. To facilitate investigations of the functional roles of this structural motif, two GPI analogues containing unnatural βGlcN(1,6)Ins, instead of αGlcN(1,6)Ins, and an alkyne group at different positions of the GPI core were designed and synthesized. To this end, an orthogonally protected pseudopentasaccharide derivative of GPIs with the βGlcN(1,6)Ins motif was convergently constructed via [3 + 2] glycosylation and used as the common intermediate to prepare both GPI analogues by streamlined synthetic protocols. The pseudopentasaccharide intermediate and developed protocols can be widely applicable to access various GPI analogues with the βGlcN(1,6)Ins motif. The target GPI analogues contain an alkyne, which allows their further modification to introduce various molecular labels via click chemistry, making them useful probes for the study of GPI anchorage. The differences in reactivity and NMR behavior of the two GPI analogues, as well as the differences of these analogues from previously reported GPI derivatives of similar structure containing an αGlcN(1,6)Ins motif, suggest that the 2-O-phosphoethanolamine moiety on mannose-I and the linkage form of GlcN in GPIs can have a decisive impact on the structure, which is likely relevant to biology.