Aryl 4,6-O-arylidene-1-thio-β-d-glycopyranoside-based new organogelators and their gels

Chemical synthesis of oligosaccharide derivatives with partial structure of β1-3/1-6 glucan, using monomeric units for the formation of β1-3 and β1-6 glucosidic linkages

β1-3/1-6 Glucans, known for their diverse structures, comprise a β1-3-linked main chain and β1-6-linked short branches. Laminarin, a β1-3/1-6 glucan extracted from brown seaweed, for instance, includes β1-6 linkages even in the main chain. The diverse structures provide various beneficial functions for the glucan. To investigate the relationship between structure and functionality, and to enable the characterization of β1-3/1-6 glucan-metabolizing enzymes, oligosaccharides containing the exact structures of β1-3/1-6 glucans are required. We synthesized the monomeric units for the synthesis of β1-3/1-6 mixed-linked glucooligosaccharides. 2-(Trimethylsilyl)ethyl 2-O-benzoyl-4,6-O-benzylidene-β-d-glucopyranoside served as an acceptor in the formation of β1-3 linkages. Phenyl 2-O-benzoyl-4,6-O-benzylidene-3-O-(tert-butyldiphenylsilyl)-1-thio-β-d-glucopyranoside and phenyl 2,3-di-O-benzoyl-4,6-di-O-levulinyl-1-thio-β-d-glucopyranoside acted as donors, synthesizing acceptors suitable for the formation of β1-3- and β1-6-linkages, respectively. These were used to synthesize a derivative of Glcβ1-6Glcβ1-3Glcβ1-3Glc, demonstrating that the proposed route can be applied to synthesize the main chain of β-glucan, with the inclusion of both β1-3 and β1-6 linkages.

Stereoselective Synthesis of Diglycosyl Diacylglycerols with Glycosyl Donors Bearing a β-Stereodirecting 2,3-Naphthalenedimethyl Protecting Group

Diglycosyl diacylglycerols (DGDGs) are major components of Gram-positive bacterial plasma membranes and are involved in the immune response systems. The chemical synthesis of DGDGs has been highly demanded, as it will allow the elucidation of their biological functions at the molecular level. In this study, we have developed a novel β-stereodirecting 2,3-naphthalenedimethyl (NapDM) protecting group that is orthogonal to protecting groups commonly used in oligosaccharide synthesis. The NapDM group can be easily cleaved under TFA-mediated acidic conditions. Futhermore, we demonstrated the application of this protecting group to an acyl protecting-group-free strategy by utilizing the NapDM group for the synthesis of DGDGs. This strategy features the use of the β-stereodirecting NapDM group as an acid-cleavable permanent protecting group and late-stage glycosylation of monoglycosyl diacylglycerol acceptors, enabling the stereoselective synthesis of three different bacterial DGDGs with unsaturated fatty acid chain(s).

Synthesis of three deoxy-sophorose derivatives for evaluating the requirement of hydroxy groups at position 3 and/or 3' of sophorose by 1,2-β-oligoglucan phosphorylases

Sophorose (Sop₂) is known as a powerful inducer of cellulases in Trichoderma reesei, and in recent years 1,2-β-D-oligoglucan phosphorylase (SOGP) has been found to use Sop₂ in synthetic reactions. From the structure of the complex of SOGP with Sop₂, it was predicted that both the 3-hydroxy group at the reducing end glucose moiety of Sop₂ and the 3'-hydroxy group at the non-reducing end glucose moiety of Sop₂ were important for substrate recognition. In this study, three kinds of 3- and/or 3'-deoxy-Sop₂ derivatives were synthesized to evaluate this mechanism. The deoxygenation of the 3-hydroxy group of D-glucopyranose derivative was performed by radical reduction using a toluoyl group as a leaving group. The utilization of a toluoyl group that plays two roles (a leaving group for the deoxygenation and a protecting group for a hydroxy group) resulted in efficient syntheses of the three target compounds. The NMR spectra of the two final compounds (3-deoxy- and 3,3'-dideoxy-Sop₂) suggested that the glucose moiety of the reducing end of Sop₂ can easily take on a furanose structure (five-membered ring structure) by deoxygenation of the 3-hydroxy group of Sop₂. In addition, the ratio of the five- and six-membered ring structures changed depending on the temperature. The SOGPs exhibited remarkably lower specific activity for 3'-deoxy- and 3,3'-dideoxy-Sop₂, indicating that the 3'-hydroxy group of Sop₂ is important for substrate recognition by SOGPs.

Synthesis and immunological evaluation of a low molecular weight saccharide with TLR-4 agonist activity

The paucity of FDA approved adjuvants renders the synthesis, characterization, and use of new compounds as vaccine adjuvants, a necessity. For this purpose, a novel saccharide analog has been synthesized from glucosamine, pyruvylated galactose and 1,4-cyclohexanediol and its biological efficacy was determined in innate immune cells. More specifically, we assessed the production of pro-inflammatory cytokines from the murine monocyte cell line, Raw 264.7 and from C57 BL/6 mouse peritoneal macrophages following exposure to the saccharide analog. Our data conclude that the novel saccharide has immunostimulatory activity on mouse macrophages as indicated by the elevated levels of IL-6 and TNF-α in culture supernatants. This effect was TLR-4-dependent but TLR-2-independent. Our data, suggest TLR-4 agonism; a key feature of vaccine adjuvants.

Xylitol based phase selective organogelators for potential oil spillage recovery

Xylitol based cost effective and easily synthesizable phase selective gelators were developed for strong gelation ability for different crude oils, wide range of refinery products and reported for their potential application in oil spillage recovery.

Enantiomeric organogelators from d-/l-arabinose for phase selective gelation of crude oil and their gel as a photochemical micro-reactor

Easy access via single steps to each enantiomer of a simple chiral organogelator, their gelation abilities and applications are reported.

Efficient activation of thioglycosides with N-(p-methylphenylthio)-ε-caprolactam-TMSOTf

N-(p-Methylphenylthio)-ε-caprolactam (1) in combination with trimethylsilyl trifluoromethanesulfonate (TMSOTf) provides an efficient thiophilic promoter system, capable of activating different thioglycosides. Both 'armed' and 'disarmed' thioglycosyl donors were activated for glycosidic bond formation. Notably, this reagent combination works well in reactivity-based one-pot oligosaccharide assembly strategy.