Synthetic studies on glycosidic phytotoxins. Part IV Synthetic studies on rhynchosporoside and related substances.

Sugawara, Fumio; Nakayama, Haruhiko; Strobel, Gary A.; Ogawa, Tomoya

doi:10.1271/bbb1961.50.2251

Cited by 5 publications

(1 citation statement)

References 2 publications

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“…Its benzylation followed by anomeric deallylation and imidate formation gave the fucofuranosyl donor 16. Coupling of monosaccharides 16 and 18 (obtained from diol 17 [32] by regioselective oxidation of the primary OH group at C-6, see the Supporting Information) in the presence of TMSOTf gave stereoselectively a-linked disaccharide 19. Deprotected disaccharide 20 was obtained by hydrogenolysis and saponification of product 19, which can be regarded as a convenient block for the assembly of larger oligosaccharides via O-deallylation followed by transformation into glycosyl donor derivatives.…”

Section: -O-benzyl-b-d-galactopyranosidementioning

confidence: 99%

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

Krylov

Argunov

Vinnitskiy

et al. 2014

Chemistry A European J

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Great interest in natural furanoside-containing compounds has challenged the development of preparative methods for their synthesis. Herein a novel reaction in carbohydrate chemistry, namely a pyranoside-into-furanoside (PIF) rearrangement permitting the transformation of selectively O-substituted pyranosides into the corresponding furanosides is reported. The discovered process includes acid-promoted sulfation accompanied by rearrangement of the pyranoside ring into a furanoside ring followed by solvolytic O-desulfation. This process, which has no analogy in organic chemistry, was shown to be a very useful tool for the synthesis of furanoside-containing complex oligosaccharides, which was demonstrated by synthesizing disaccharide derivatives α-D-Galp-(1→3)-β-D-Galf-OPr, 3-O-s-lactyl-β-D-Galf-(1→3)-β-D-Glcp-OPr, and α-L-Fucf-(1→4)-β-D-GlcpA-OPr related to polysaccharides from the bacteria Klebsiella pneumoniae and Enterococcus faecalis and the brown seaweed Chordaria flagelliformis.

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Section: -O-benzyl-b-d-galactopyranosidementioning

confidence: 99%

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

Krylov

Argunov

Vinnitskiy

et al. 2014

Chemistry A European J

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Synthesis ofStreptococcus pneumoniae Type 3 Neoglycoproteins Varying in Oligosaccharide Chain Length, Loading and Carrier Protein

2001

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The preparation is described of a range of neoglycoproteins containing synthesised fragments of the capsular polysaccharide of Streptococcus pneumoniae type 3, that is beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1-->O)-(CH2)3NH2 (1), beta-D-Glcp-(1-->3)-beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1-->O)-(CH2)3NH2 (2), and beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1-->3)-beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1-->O)-(CH4)NH2 (3). A blockwise approach was developed for the synthesis of the protected carbohydrate chains, in which the carboxylic groups were introduced prior to deprotection by selective oxidation of HO-6 in the presence of HO-4 by using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy radical). After deprotection, the 3-aminopropyl spacer of the fragments was elongated with diethyl squarate (3,4-diethoxy-3-cyclobutene-1,2-dione) and the elongated oligosaccharides were conjugated to CRM197 (cross-reacting material of diphtheria toxin), KLH (keyhole limpet hemocyanin) or TT (tetanus toxoid). The resulting neoglycoconjugates varied in oligosaccharide chain length, oligosaccharide loading and protein carrier. These well-defined conjugates are ideal probes for evaluating the influence of the different structural parameters in immunological tests.

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The Total Synthesis of Glycolipids from Streptococcus pneumoniae and a Re‐evaluation of Their Immunological Activity**

et al. 2022

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Invariant natural killer (iNK) T cells, Type I iNKTs, are responsible for the production of pro‐inflammatory cytokines which induce a systemic immune response. They are distinctive in possessing an semi‐invariant T‐cell receptor that recognizes glycolipid antigens presented by CD1d, a protein closely related to the class I major histocompatibility complex, conserved across multiple mammalian species in a class of proteins well‐renowned for their high degree of polymorphism. This receptor's first potent identified antigen is the α‐galactosylceramide, KRN7000, a synthetic glycosphingolipid closely related to those isolated from bacteria that were found on a Japanese marine sponge. A corresponding terrestrial antigen remained unidentified until two specific diacylglycerol‐containing glycolipids, reported to activate iNKT cells, were isolated from Streptococcus pneumoniae. We report the total synthesis and immunological re‐evaluation of these two glycolipids. The compounds are unable to meaningfully activate iNKT cells. Computational modelling shows that these ligands, while being capable of interacting with the CD1d receptor, create a different surface for the binary complex that makes formation of the ternary complex with the iNKT T‐cell receptor difficult. Together these results suggest that the reported activity might have been due to an impurity in the original isolated sample and highlights the importance of taking care when reporting biological activity from isolated natural products.

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Synthetic studies on glycosidic phytotoxins. Part IV Synthetic studies on rhynchosporoside and related substances.

Cited by 5 publications

References 2 publications

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

Synthesis ofStreptococcus pneumoniae Type 3 Neoglycoproteins Varying in Oligosaccharide Chain Length, Loading and Carrier Protein

The Total Synthesis of Glycolipids from Streptococcus pneumoniae and a Re‐evaluation of Their Immunological Activity**

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