Keio University · Chemistry
Professor Kazunobu Toshima's research lab specializes in synthetic organic chemistry, with a primary focus on the development of innovative glycosylation methodologies for the efficient synthesis of complex natural products. The lab is renowned for pioneering regio- and stereoselective glycosylation strategies using unique catalysts such as boronic acids and quinones, enabling the selective formation of 1,2-cis-glycosidic linkages in unprotected substrates. Their work has significantly advanced the synthesis of biologically active glycosides, including isoflavone glycosides and complex oligosaccharides like the lipopolysaccharide repeating unit from *E. coli* O75. The lab also explores DNA-cleaving systems based on quinoxaline derivatives, highlighting their interdisciplinary approach to glycochemistry and molecular recognition.
Figures are computed from collected data and may differ slightly.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRecent progress in O-glycosylation methods and its application to natural products synthesisKazunobu Toshima and Kuniaki TatsutaCite this: Chem. Rev. 1993, 93, 4, 1503–1531Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://pubs.acs.org/doi/10.1021/cr00020a006https://doi.org/10.1021/cr00020a006research-articleACS PublicationsRequest reuse permissionsArticle Views6987Altmetric-Citations
Quinoxaline, found in antitumor quinoxaline antibiotics, was found to cleave double stranded DNA at the 5' side guanine of 5'-GG-3' site on irradiation with long wavelength UV light without any additive; furthermore, a bis(quinoxaline-carbohydrate) hybrid system was very effective for DNA cleavage.
Regio- and 1,2- cis-stereoselective chemical glycosylation of unprotected glycosyl acceptors has been in great demand for the efficient synthesis of natural glycosides. However, simultaneously regulating these selectivities has been a longstanding problem in synthetic organic chemistry. In nature, glycosyl transferases catalyze regioselective 1,2- cis-glycosylations via the S<sub>N</sub>i mechanism, yet no useful chemical glycosylations based on this mechanism have been developed. In this paper,
Regioselective and 1,2-cis-α-stereoselective glycosylations using 1α,2α-anhydro glycosyl donors and diol glycosyl acceptors in the presence of a glycosyl-acceptor-derived boronic ester catalyst. The reactions proceed smoothly to give the corresponding 1,2-cis-α-glycosides with high stereo- and regioselectivities in high yields without any further additives under mild reaction conditions. In addition, the present glycosylation method was successfully applied to the synthesis of an isoflavone glyc
Regio- and stereoselective β-mannosylations using 1,2-anhydromannose and diol sugar acceptors in the presence of a boronic acid catalyst proceeded smoothly to give the corresponding β-mannosides with high regio- and β-stereoselectivities in high yields without further additives under mild conditions. In addition, this glycosylation method was applied successfully to the synthesis of a tetrasaccharide repeating unit of lipopolysaccharide (LPS) derived from E. coli O75.
O-Glycosidations of glycals 1, 8 and 9 with several alcohols by using a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) under neutral conditions proceeds smoothly to give the corresponding 2,3-unsaturated glycosides in high yields.
Sugar sugar: In the glycosylation of racemic alcohols with 1 using the chiral phosphoric acid 2 as an activator, one enantiomer of the racemic alcohol selectively reacts with 1 to give the corresponding glycoside with good to excellent α/β-stereo- and diastereoselectivity in high yield. The reaction was successfully applied to the synthesis of a chiral natural flavan glycoside using a racemic aglycon.
Low-molecular weight type I and II fucoidan derivatives with different sulfation patterns were designed and systematically synthesized from the corresponding common key intermediate and their anti-proliferative activities and apoptosis-inducing activities against human breast cancer (MCF-7) and human cervical epithelioid carcinoma (HeLa) cells were evaluated. Our results demonstrated that one of the type II fucoidan derivatives, 9, effectively reduced the number of viable MCF-7 and HeLa cells in
The highly stereoselective total synthesis of the macrolide antibiotic, bafilomycin A(1) (1), the first specific potent inhibitor of vacuolar H(+)-ATPase, has been achieved by a convergent route involving the synthesis and coupling of its 16-membered tetraenic lactone and beta-hydroxyl hemiacetal side-chain subunits. The C1-C17 16-membered lactone aldehyde 2 was synthesized through the coupling of the C5-C11 vinyl iodide 4 and the C12-C17 vinylstannane 5, followed by construction of the C1-C4 di
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 <sup>13</sup> C kinetic i
The O-glycosidations of glycals, 3,4-di-O-acetyl-L-rhamnal (1) and 3,4,6-tri-O-acetyl-D-glucal (2), with several alcohols using an acidic clay, montmorillonite K-10, as an environmentally acceptable and inexpensive industrial catalyst under mild conditions proceeded effectively to give the corresponding 2,3-unsaturated O-glycosides in high yields.
Abstract Antibiotic elaiophylin (1) has been first synthesized by a convergent route involving aldol coupling of (5R,6R,7R)-5-O-[2-deoxy-3,4-bis-O-(isopropyldimethylsilyl)-α-l-fucopyranosyl]-6-ethyl-7-O-(diethylisopropylsilyl)-5,7-dihydroxy-3-octanone (25f) and (7S,8S,15S,16S:3E,5E,11E,13E)-8,16-bis[(1R)-1-formylethyl]-7,15-dimethyl-1,9-dioxa-3,5,11,13-cyclohexadecatetraene-2,10-dione (3), followed by desilylation. The appropriately O-protected segment 25f and the macrocyclic dialdehyde 3 were s
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of Highly Stereocontrolled Glycosidations Employing 2,6-Anhydro-2-thio Sugars to the Syntheses of Erythromycin A and Olivomycin A TrisaccharideKazunobu Toshima, Yuko Nozaki, Satsuki Mukaiyama, Tetsuro Tamai, Masaya Nakata, Kuniaki Tatsuta, and Mitsuhiro KinoshitaCite this: J. Am. Chem. Soc. 1995, 117, 13, 3717–3727Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://pubs.a
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