Published papers

© 2020 Wiley-VCH GmbH Avian pathogenic Escherichia coli (APEC) is a common bacterial pathogen infecting chickens, resulting in economic losses to the poultry industry worldwide. In particular, APEC O1, one of the most common serotypes of APEC, is considered problematic due to its zoonotic potential. Therefore, many attempts have been made to develop an effective vaccine against APEC O1. In fact, the lipopolysaccharide (LPS) O-antigen of APEC O1 has been shown to be a potent antigen for inducing specific protective immune responses. However, the detailed structure of the O-antigen of APEC O1 is not clear. The present study demonstrates the first synthesis of a pentasaccharide repeating unit of LPS derived from virulent E. coli O1 and its conjugate with BSA. ELISA tests using the semi-synthetic glycoconjugate and the APEC O1 immune chicken serum revealed that the pentasaccharide is a glycotope candidate of APEC O1, with great potential as an antigen for vaccine development. This paper was press-released from Keio University. (https://www.keio.ac.jp/ja/press-releases/2020/11/16/28-76321/) This paper was selected as a Hot Paper. This paper was selected as an inside back cover.

Regio- and 1,2-cis-α-stereoselective glycosylations were investigated using 1,2-anhydroglucose donors and trans-1,2-diol sugar acceptors in the presence of a diboron catalyst. The reactions proceeded smoothly to provide the corresponding 1,2-cis-α-glycosides with consistently very high stereoselectivity and were regioselectivity controlled by the protecting groups of the acceptor. The present glycosylation method was applied successfully to the efficient synthesis of α-1,3-glucan pentasaccharide.

© 2020 Wiley-VCH GmbH A 2-naphthol derivative 2 corresponding to the aromatic ring moiety of neocarzinostatin chromophore was found to degrade proteins under photo-irradiation with long-wavelength UV light without any additives under neutral conditions. Structure–activity relationship studies of the derivative revealed that methylation of the hydroxyl group at the C2 position of 2 significantly suppressed its photodegradation ability. Furthermore, a purpose-designed synthetic tumor-related biomarker, a H2O2-activatable photosensitizer 8 possessing a H2O2-responsive arylboronic ester moiety conjugated to the hydroxyl group at the C2 position of 2, showed significantly lower photodegradation ability compared to 2. However, release of the 2 from 8 by reaction with H2O2 regenerated the photodegradation ability. Compound 8 exhibited selective photo-cytotoxicity against high H2O2-expressing cancer cells upon irradiation with long-wavelength UV light.

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Stereospecific β-l-rhamnopyranosylations were conducted using a 1,2-anhydro-l-rhamnopyranose donor and mono-ol or diol acceptors in the presence of a glycosyl-acceptor-derived borinic or boronic ester. Reactions proceeded smoothly to provide the corresponding β-l-rhamnopyranosides (β-l-Rhap) with complete stereoselectivity in moderate to high yields without any further additives under mild conditions. Mechanistic studies of the borinic ester mediated glycosylation using 13C kinetic isotope effect (KIE) measurements and DFT calculations were consistent with a concerted SNi mechanism with an exploded transition state. In addition, the present glycosylation method was applied successfully to the synthesis of a trisaccharide, α-l-Rhap-(1,2)-β-l-Rhap-(1,4)-Glcp, derived from Streptococcus pneumoniae serotypes 7B, 7C, and 7D.

© 2020, The Author(s). Chemical desymmetrization reactions of meso-diols are highly effective for the precise and efficient synthesis of chiral molecules. However, even though enzyme-catalyzed desymmetric glycosylations are frequently found in nature, there is no method for highly diastereoselective desymmetric chemical glycosylation of meso-diols. Herein, we report a highly diastereoselective desymmetric 1,2-cis-glycosylation of meso-diols found in myo-inositol 1,3,5-orthoesters using a boronic acid catalyst based on predictions of regioselectivity by density functional theory (DFT) calculations. The enantiotopic hydroxyl groups of the meso-diols are clearly differentiated by the stereochemistry at the C2 position of the glycosyl donor with excellent regioselectivities. In addition, the present method is successfully applied to the synthesis of core structures of phosphatidylinositolmannosides (PIMs) and glycosylphosphatidylinositol (GPI) anchors, and common β-mannoside structures of the LLBM-782 series of antibiotics.

The first total synthesis of vineomycin A1 (1) has been accomplished. Structure–activity relationship studies for cytotoxicity against human breast cancer MCF-7 cells using several synthetic vineomycin A1 analogues differing in the number and position of glycon moieties revealed that the cytotoxicity increased as the number of glycon moieties increased. The position of the glycon moiety was one of the key factors for the cytotoxicity of 1. Moreover, in vitro analysis of the cytotoxicity of 1 against MCF-7 cells indicated for the first time that 1 effectively induced cancer cell death by apoptosis, not by acting as a DNA intercalating agent.

© 2018 The Royal Society of Chemistry. 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.

© 2018 The Royal Society of Chemistry. A purpose-designed anthraquinone-horseradish peroxidase (HRP)-cell penetrating peptide hybrid 1 showed high and effective cell permeability. Furthermore, 1 exhibited enzymatic activity without photo-irradiation, whereas significant self-degradation and loss of enzymatic activity occurred upon photo-irradiation in living cells.

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Purpose-designed 2-phenylquinoline (PQ)-sugar hybrids 1 and 2 were synthesized and evaluated for their photodegradation activities against an α-glucosidase target. The results indicated that PQ-mannose hybrid 2 selectively and effectively photodegraded α-glucosidase and significantly inhibited its enzymatic activity upon irradiation with long-wavelength UV light in the absence of any additives under neutral and aqueous conditions. Furthermore, 2 selectively and effectively inhibited α-glucosidase activity only with photo-irradiation even in complex cell lysate.