Hiroyuki Iijima

Stereoselective total synthesis of glycopeptides bearing the dimeric and trimeric sialosyl-Tn epitope☆

The dimeric and trimeric sialosyl-Tn epitopes, [alpha-D-Neup5Ac-(2----6)-alpha-D-GalpNAc-(1----3)-L-Ser]n-L-Val (n = 2 and 3), which represent part of a clustered carbohydrate region of glycophorin A, a human erythrocyte glycoprotein, have been synthesised stereoselectively. 2-Azido-3-O-benzyl-4,6-O-benzylidene-2-deoxy-D-galactopyranosyl fluoride (GalpNAc unit), Fmoc-L-serine phenacyl ester (Ser unit), and benzyl 5-acetamido-4,7,8,9-tetra-O-benzyl-5-deoxy-3-S-phenyl-3-thio-D-erythro-L - gluco-2-nonulopyranosylonate bromide (Neup5Ac unit) were the key intermediates for stereoselective glycosylation. 2-Ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline-promoted elongation of the peptide chain and then hydrogenolysis afforded the title compounds.

Total synthesis of 3-O-[2-acetamido-6-O-(N-acetyl-α-d-neuraminyl)-2-deoxy-α-d-galactosyl]-l-serine and a stereoisomer☆

Abstract O -(5-Acetamido-3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosylonic acid)-(2→6)- O -(2-acetamido-2-deoxy-α- d -galactopyranosyl)-(1→3)- l -serine, a structural unit occurring in various submaxillary mucins, was synthesized for the first time by using O -[methyl (5-acetamido-4,7,8,9-tetra- O -acetyl-3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl)onate]-(2→6)-3,4-di- O -acetyl-2- azido-2-deoxy- d -galactopyranosyl trichloroacetimidate ( 13 ) and N -(benzyloxycarbonyl)- l -serine benzyl ester as the key intermediates. The trichloroacetimidate 13 was prepared by starting from two monosaccharide synthons, namely, ally 2-azido-2-deoxy-β- d -galactopyranoside and methyl (5-acetamido-4,7,8,9-tetra- O -acetyl-3,5-dideoxy- d - glycero -β- d - galacto -2-nonulopyranosyl chloride)onate, which were coupled in the presence of silver triflate in tetrahydrofuran to give the desired α-(2→6)-linked disaccharide in moderate selectivity.

A highly stereoselective synthesis of di- and trimeric sialosyltn epitope: A partial structure of glycophorin A

Abstract Di- and trimeric sialosyl-Tn epitope, prototype molecules of O-linked (mucin type) sialoglycoproteins, were synthesized in a stereocontrolled manner.

Synthesis of human M blood group antigenic glycopeptide

Abstract A first total synthesis of N-terminal glycoheptapeptide of human glycophorin A m was accomplished by solution phase peptide condensation utilizing the tetrasaccharide-linked amino acid building blocks designed for Fmoc strategy.

Synthesis of a mucin-type O-glycosylated amino acid, β-Gal-(1→3)-[α-Neu5Ac-(2→6)]-α-GalNAc-(1→3)-Ser☆

Abstract Total synthesis of O -β- d -galactopyranosyl-(1→3)- O -[(5-acetamido-3,5-dideoxy- d - glycero -α- galacto -2-nonulopyranosylonic acid)-(2→6)]- O -(2-acetamido-2-deoxy-α- d -galactopyranosyl)-(1→3)- l -serine was achieved by use of the key glycosyl donor O -(2,3,4,6-tetra- O -acetyl-β- d -galactopyranosyl)-(1→3)- O -[methyl (5-acetamido-4,7,8,9-tetra- O -acetyl-3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl) onate-(2→6)]-4- O -acetyl-2-azido-2-deoxy-α- d -galactopyranosyl trichloroacetimidate and the key glycosyl acceptor N -(benzyloxycarbonyl)- l -serine benzyl ester in a regiocontrolled way.

Synthesis of the N-terminal glycopentapeptides of human glycophorin am and an carrying trimeric sialosyl Tn epitope

Abstract Pentapeptides with a cluster of sialosyl Tn epitopes, designed as models for MN blood group antigenic determinants of human glycophorin A, were synthesized in a stereocontrolled manner.

Synthesis of a fully protected derivative of O-(N-acetyl-α-d-neuraminyl)-(2→3)-O-β-d-galactopyranosyl-(1→3)-O- [(N-acetyl-α-d-neuraminyl)-(2→6)]-O-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-(1→3)-l-serine

Abstract N -(Benzyloxycarbonyl)- O -[methyl (5-acetamido-4,7,8,9-tetra- O -acetyl-3,5- dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl)onate]-(2→3)- O -(2,4,6-tri- O - acetyl-β- d -galactopyranosyl)-(1→3)- O -[methyl (5-acetamido-4,7,8,9-tetra- O - acetyl-3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl)onate-(2→6)]- O -(2- acetamido-4- O -acetyl-2-deoxy-α- d -galactopyranosyl)-(1→3)- l -serine benzyl ester was synthesized by using O -[methyl (5-acetamido-4,7,8,9-tetra- O -acetyl-3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl)onate]-(2→3)- O -(2,4,6-tri- O -acetyl- β- d -galactopyranosyl)-(1→3)- O -[methyl (5-acetamido-4,7,8,9-tetra- O -acetyl- 3,5-dideoxy- d - glycero -α- d - galacto -2-nonulopyranosyl)onate-(2→6)]-4- O -acetyl-2- azido-2-deoxy-α- and -β- d -galactopyranosyl trichloroacetimidate as a key glycotetraosyl donor which, upon reaction with N -(benzyloxycarbonyl)- l -serine benzyl ester, afforded a 44% yield of a mixture of the α- and β-glycosides in the ratio of 2:5.

Synthesis of a glycotetraosyl serine, a partial structure of an ovarian cyst mucin glycoprotein of blood group A activity

Abstract A glycotetraosyl serine containing blood group A determinant tetrasaccharide and its properly protected equivalent were synthesized in a regio- and stereocontrolled manner.

Phenoxenium ions identical intermediates in the acid-catalyzed solvolysis of n-tosyl-O-Arylhydroxylamines and in the thermolysis of N-Aryloxypyridinium salts

Abstract The acid-catalyzed solvolysis of N-tosyl-O-arylhydroxylamines in aromatic solvents and the thermolysis of N-arylqxypyridinium salts involve common intermediates, phenoxenium ions, for the formation of hydroxybiphenyl derivatives. Diphenylethers are formed when the hydrolysis of the N—O bonds is slow and the aromatic solvent has high nucleophilicity.