Kazunobu Toshima 교수

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_Ni 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 ¹³ 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