Published papers

Motobamide (1), a new cyclic peptide containing a C-prenylated cyclotryptophan residue, was isolated from a marine Leptolyngbya sp. cyanobacterium. Its planar structure was established by spectroscopic and MS/MS analyses. The absolute configuration was elucidated based on a combination of chemical degradations, chiral-phase HPLC analyses, spectroscopic analyses, and computational chemistry. Motobamide (1) moderately inhibited the growth of bloodstream forms of Trypanosoma brucei rhodesiense (IC50 2.3 μM). However, it exhibited a weaker cytotoxicity against normal human cells (IC50 55 μM).

Among a series of chemically synthesized fucoidan derivatives (1-9), 5 was found for the first time to bind to influenza virus hemagglutinins (HAs) and inhibit hemagglutination activity. In addition, a designed C3-symmetric tripodal ligand 10, synthesized with three sulfated oligofucoside moieties of 5, exhibited much greater hemagglutination inhibition activity than 5. A plaque assay using MDCK cells demonstrated that 10 effectively inhibited influenza virus infection.

Synthetic glyco-ligands are promising candidates for effective nanomedicines against pathogens. Glycopolymers bearing sialyl-oligosaccharides interact with hemagglutinin present on the surface of influenza viruses. In designing new glycopolymers that further enhance the interaction with viruses, both static and dynamic properties of the glycopolymers should be considered. In this report, we evaluated the correlation between dynamic properties of glycopolymers and their interaction with the influenza virus. Glycopolymers with pendant sialyllactoses and various linker structures were synthesized, and their molecular mobility was determined by proton spin-spin relaxation time measurements. The molecular mobility of the glycounits increased as the length of the linker structures increased. Interestingly, glycopolymers with the medium-length linker structure exhibited the strongest interaction with the influenza virus, suggesting that optimal molecular mobility is required for maximizing multivalent interactions with the target.

The precise design of synthetic polymer ligands using controlled polymerization techniques provides an advantage for the field of nanoscience. We report the topological design of glyco-ligands based on synthetic polymers for targeting hemagglutinin (HA, lectin on the influenza virus). To achieve precise arrangement of the glycounits toward the sugar-binding pockets of HA, triarm star glycopolymers were synthesized. The interaction of the star glycopolymers with HA was found to depend on the length of the polymer arms and was maximized when the hydrodynamic diameter of the star glycopolymer was comparable to the distance between the sugar-binding pockets of HA. Following the formula of multivalent interaction, the number of binding sites in the interaction of the glycopolymers with HA was estimated as 1.8-2.7. Considering one HA molecule has three sugar-binding pockets, these values were reasonable. The binding mode of synthetic glycopolymer-ligands toward lectins could be tuned using controlled radical polymerization techniques.