An approach for direct synthesis of biologically significant 2-deoxy-β-glycosides has been developed via O-alkylation of a variety of 2-deoxy-sugar-derived anomeric alkoxides using challenging secondary triflates as electrophiles. It was found a free hydroxyl group at C3 of the 2-deoxy-sugar-derived lactols is required in order to achieve synthetically efficient yields. This method has also been applied to the convergent synthesis of a 2-deoxy-β-tetrasaccharide.
Low-molecular-weight gelators are interesting small molecules with potential applications as advanced materials. Carbohydrate-based small molecular gelators are especially useful because they are derived from renewable resources and are more likely to be biocompatible and biodegradable. Various 4,6-benzylidene acetal protected α-methyl 2-d-glucosamine derivatives have been found to be effective low-molecular-weight gelators. To understand the influence of the 4,6-benzylidene acetal functional group toward molecular self-assembly and to obtain effective molecular gelators, we synthesized and analyzed a new series of d-glucosamine derivatives in which the phenyl group of the acetal is replaced by a benzyl group. The homologation of the acetal protection from aromatic to aliphatic functional groups allows us to probe the effect of increasing structural flexibility on molecular self-assembly and gelation. In this study, nine representative amides and nine urea analogs were synthesized, and their gelation properties were analyzed in a series of organic solvents and aqueous solutions. The resulting amide and urea derivatives are versatile organogelators forming gels in toluene, ethanol, isopropanol, ethylene glycol, and aqueous mixtures of organic solvents. More interestingly, the amide analogs are also effective gelators for pump oil and engine oil. NMR spectroscopy at variable temperatures was used to analyze the molecular assemblies and intermolecular forces. The selected gelators with several drug and dye molecules in DMSO and water were studied for their effectiveness of encapsulation and release of these agents.
A mild and atom-economic gold(I)-catalyzed glycosylation for stereoselective synthesis of 2-deoxy αglycosides using bench-stable 2-deoxy S-But-3-ynyl thioglycoside donors has been described. Under optimal conditions, 2deoxy and 2,6-dideoxy thioglycoside donors were able to react with a variety of primary, secondary, and tertiary alcohol acceptors to afford α-selective glycosides in good to excellent yields.
A mild and atom-economic rhenium(V)-catalyzed stereoselective synthesis of β-D-digitoxosides from 6-deoxy-D-allals has been described. This β-selective glycosylation was achieved probably because of the formation of corresponding α-digitoxosides disfavored by 1,3-diaxial interaction. In addition, this method has been successfully applied to the synthesis of digitoxin trisaccharide glycal for the direct synthesis of digitoxin and C1'-epi-digitoxin.
Despite the role of the stringent response in antibiotic survival and recurrent infections, it has been a challenging target for antibacterial therapies because it is so ubiquitous. This is an especially relevant consideration for the treatment of
Clostridioides difficile
infection (CDI), as exposure to broad-spectrum antibiotics that harm commensal microbes is a major risk factor for CDI.
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