The use of O-glycosyl trichloroacetimidates in the synthesis of unsymmetrical trehalose analogues

Synthesis of isobemisiose, neosartose, and fischerose: three α-1,6-linked trehalose-based oligosaccharides identified from Neosartorya fischeri

Three complex α-1,6-linked trehalose-based oligosaccharides with unique preservation properties, isobemisiose, neosartose, and fischerose, were recently identified from the extreme stress-tolerant ascospores of Neosartorya fischeri. Herein, we report the first concise, scalable, and iterative chemical synthesis of these oligosaccharides from a differentially protected thioglycoside donor and a selectively protected, asymmetric trehalose acceptor. This work constitutes an improved synthesis of isobemisiose, and is also the first reported synthesis of neosartose, a tetrasaccharide, and fischerose, a pentasaccharide, in good yield. Importantly, in-depth studies of biological function are enabled by this synthetic platform.

Tailoring Trehalose for Biomedical and Biotechnological Applications

Trehalose is a non-reducing sugar whose ability to stabilize biomolecules has brought about its widespread use in biological preservation applications. Trehalose is also an essential metabolite in a number of pathogens, most significantly the global pathogen Mycobacterium tuberculosis, though it is absent in humans and other mammals. Recently, there has been a surge of interest in modifying the structure of trehalose to generate analogues that have applications in biomedical research and biotechnology. Non-degradable trehalose analogues could have a number of advantages as bioprotectants and food additives. Trehalose-based imaging probes and inhibitors are already useful as research tools and may have future value in the diagnosis and treatment of tuberculosis, among other uses. Underlying the advancements made in these areas are novel synthetic methods that facilitate access to and evaluation of trehalose analogues. In this review, we focus on both aspects of the development of this class of molecules. First, we consider the chemical and chemoenzymatic methods that have been used to prepare trehalose analogues and discuss their prospects for synthesis on commercially relevant scales. Second, we describe ongoing efforts to develop and deploy detectable trehalose analogues, trehalose-based inhibitors, and non-digestible trehalose analogues. The current and potential future uses of these compounds are discussed, with an emphasis on their roles in understanding and combatting mycobacterial infection.

Unusually Stable Picoloyl-Protected Trimethylsilyl Glycosides for Nonsymmetrical 1,1'-Glycosylation and Synthesis of 1,1'-Disaccharides with Diverse Configurations

Nonsymmetrical 1,1'-disaccharides and related derivatives constitute structural components in various glycolipids and natural products. Some of these compounds have been shown to exhibit appealing biological properties. We report a direct yet stereoselective 1,1'-glycosylation strategy for the synthesis of nonsymmetrical 1,1'-disaccharides with diverse configurations and sugar components. The strategy is based on the joined forces of a new class of configurationally stable glycoside acceptors and stereodirecting thioglycoside donors. The new glycoside acceptors feature a picoloyl (Pico) protecting group at the remote C4/C3 position that confers unusual stability on TMS glycosides under acidic conditions.

Strategies for desymmetrising trehalose to synthesise trehalose glycolipids

The desymmetrisation and regioselective protection of trehalose are major challenges in the chemical synthesis of biologically essential trehalose glycolipids. We reviewed the literature on desymmetrising trehalose to synthesise trehalose glycolipids and highlighted an efficient regioselective 6-O-phosphorylation method that can be applied to synthesise asymmetric trehalose glycolipids.

Synthesis of the anti-virus compound shuangkangsu's analogs

Four novel cyclic peroxide glucosides 15a, 15b, 16a, and 16b, optically pure analogs of shuangkangsu (1), which is an anti-virus natural product with an unusual skeleton isolated from the buds of Lonicera japonica Thunb, were first synthesized totally in six steps including cycloaddition of furan with diethyl acetylenedicarboxylate and glycosylation.

Synthesis of L-trehalose and observations on isomer and by-product formation

With a view to gaining evidence on the mechanism by which D-trehalose is able to stabilise biomolecules towards dehydration (anhydrobiosis) and heat, L-trehalose has been prepared in order to allow comparative studies to be made. Little change can be induced in the ratio of the alpha,alpha-, alpha,beta-, beta,beta-1,1'-stereoisomers of the disaccharide formed from 2,3,4,6-tetra-O-benzyl-L-glucose by using different reaction procedures and by varying the reaction conditions. Benzyl 2,3,4,6-tetra-O-benzyl alpha- and beta-L-glucopyranoside are by-products in the trimethylsilyl trifluoromethanesulphonate mediated formation of the 1,1'-linked disaccharides.

Isobemisiose: an unusual trisaccharide abundant in the silverleaf whitefly, Bemisia argentifolii

The major soluble carbohydrates in the silverleaf whitefly, Bemisia argentifolii, were glucose, alpha,alpha-trehalose and an unknown sugar. Analysis of the unknown sugar and its chemical and enzymatic digestion products by high-performance liquid chromatography (HPLC) showed that it was probably a trisaccharide, consisting entirely of glucose, and containing both alpha,alpha-trehalose and isomaltose moieties. Matrix-assisted laser desorption mass spectrometry, mass spectrometry and 13C and 1H nuclear magnetic resonance spectroscopy confirmed that the sugar was a trisaccharide with the following structure: O-alpha-D-glucopyranosyl-(1-->6)-O-alpha-D-glucopyranosyl-(1<-->1)-alpha-D-glucopyranoside. This trisaccharide, found primarily in the bodies of B. argentifolii and not in their honeydew, is structurally similar to bemisiose [O-alpha-D-glucopyranosyl-(1-->4)-O-alpha-D-glucopyranosyl-(1<-->1)-alpha-D-glucopyranoside], a sugar first identified in Bemisia honeydew. Consequently, the common name isobemisiose is proposed for the newly identified sugar. Isobemisiose, which has not been previously reported to occur in nature, constituted as much as 46% (w/w) of the ethanol-soluble sugars in adult B. argentifolii, equivalent to approximately 10% of their dry weight. It was also found in similar quantities in immature B. argentifolii. Isobemisiose was detected in two other whitefly species and in several species of aphids, but at lesser concentrations than in B. argentifolii. Labeling and pulse-chase experiments using [14C]sucrose supplied to B. argentifolii in an artificial diet revealed that label accumulated in and was chased from isobemisiose more slowly than for either glucose or trehalose. Incubation of isobemisiose with cell-free extracts of B. argentifolii demonstrated that these whiteflies contained the necessary complement of enzymes to fully degrade isobemisiose to glucose. These labeling and digestion experiments indicate that isobemisose is probably a storage carbohydrate in B. argentifolii.

Structural determination of some new oligosaccharides and analysis of the branching pattern of isomaltooligosaccharides from beer

Separation of the low molecular weight fraction of oligosaccharides from beer and subsequent NMR analysis led to the identification of several new derivatives of trehalose, sucrose, maltooligosaccharides glucosylated at O-2 of reducing end Glc, and linear Glc oligomers with alpha-(1-->3) and alpha-(1-->4)-linkages. Reducing oligosaccharides were labeled with 7-amino-4-methylcoumarin by reductive amination, separated according to their molecular weight and the branching pattern was studied using enzymatic (pullulanase) degradation in combination with MALDI-TOF mass spectrometry and HPLC analysis. It was found that up to DP 10 isomaltooligosaccharides mostly consisted of a linear reducing alpha-(1-->4)-linked Glc chain substituted by single maltose or maltotriose residue at O-6 of any residue except the reducing one.