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101.
Condensation reaction of 3,5-di-O-benzoyl-1,2-O-(1-cyanoben-zylidene)-β-D-arabinofuranose (2) with benzyl and allyl 2,3-di-O-benzoyl-5-O-triphenylmethyl-α-L-arabinofuranosides (5a and 5b) in methylene chloride in the presence of triphenylcarbenium tetrafluoroborate as catalyst under high vacuum gave α-(1→5)-linked dimeric D-arabinofuranoside derivatives (6a and 6b). One of the dimeric compounds (6a) was debenzoylated, triphenylmethylated, and rebenzoylated to give a dimeric homolog of 5a (8). Similarly for the preparation of 6a, 8 was condensed with 2 to provide an α-(1→5)-linked trimeric D-arabinofuranoside derivative (9). Further elongation of the glycoside chain might be possible in the same way. 相似文献
102.
Kenichi Takeo Kimiko Nagayoshi Kenichi Nishimura Shinichi Kitamura 《Journal of carbohydrate chemistry》2013,32(8):1159-1177
Abstract The 8-methoxycarbonyloctyl β-glycosides of the trisaccharides O-β-d-Glcp-(1 → 6)- O-β-d-Glcp-(1 → 3)-d-Glcp and O-β-d-Glcp-(1 → 3)-O-[β-d -Glcp-(1 → 6)]-d-Glcp and of the tetrasaccharide O-β-d-Glcp-(1 → 3)-O-[β-d-Glcp-(1 → 6)]-O-β-d-Glcp-(1 → 3)-d-Glcp, corresponding to the fragments of schizophyllan, have been synthesized by using mono- to tetrasaccharide 1-thioglycosides as glycosyl donors, each bearing a participating benzoyl group in the 2-position, and N-iodosuccinimide and silver triflate as promoter. Saponification of the tri- and tetrasaccharide β-glycosides, followed by attachment to bovine serum albumin of the resulting sugar derivatives having a carboxyl group at the aglycon terminal, provided neoglycoproteins for immunological studies of the polysaccharide. 相似文献
103.
Akira Hasegawa Kenichi Ito Hideharu Ishida Makoto Kiso 《Journal of carbohydrate chemistry》2013,32(3):353-368
Abstract Four sialyl and sulfo Lex analogs containing glucose in place of N-acetylglucosamine, and a ceramide or 2-(tetradecyl)hexadecyl residue, have been synthesized. Condensation of O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylonate)-(2→3)-O-(4-O-acetyl-2,6-diO-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,4-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (1) with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3, diol (2) or 2-(tetradecyl)-hexadecyl-1-ol (3) gave the corresponding β-glycosides 4 and 7. Compound 4 was converted into the ganglioside 6 via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and saponification of the methyl ester group. Hydrolysis of the O-acyl groups in 7 followed by saponification of the methyl ester, gave sialyl Lex ganglioside analog 8 containing a branched fatty alkyl residue. On the other hand, glycosylation of O-(4-O-acetyl-2,6-di-O-benzoyl-3-O-levulinyl-β-d-galactopyranosyl)-(1→4)-[O-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (13), prepared from 2-(trimethylsilyl)ethyl O-(2,6-di-O-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-β-d-glucopyranoside (9) via selective 3-O-levulinylation, acetylation, removal of the 2-(trimethylsilyl)ethyl group, with 2 or 3, gave the desired β-glycosides 14 and 19. Selective reduction of the axido group in 14 followed by coupling with octadecanoic acid gave the ceramide derivative 16. Removal of the levulinyl group in 16 and 19, treatment with sulfur trioxide pyridine complex and subsequent hydrolysis of the protecting groups yielded the corresponding sulfo Lex analogs 18 and 21. 相似文献
104.
Ken-Ichi Kanno Yuichi Kobayashi Shin-Ichiro Nishimura Hiroyoshi Kuzuhara Kenichi Hatanaka 《Journal of carbohydrate chemistry》2013,32(4-5):481-490
Abstract 1,6-Anhydro-2-deoxy-3,4-di-O-benzyl-2-phthalimido-β-d- glucopyranose (5) was synthesized from 1,6-anhydro-β-d-mannopyranose (1) in five steps. Compound 5 was polymerized under cationic conditions and selectively yielded glucosamine oligomers (degree of polymerization 5-7). Copolymerization of 5 with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose indicated the low reactivity of 5 with the active cation derived from 5. Deprotection of 2-deoxy-3,4-di-O-benzyl-2-phthalimido-(1→6)-β-d-glucopyranan (7) and N-acetylation gave 2-acetamido-2-deoxy-(1→6)-β-d-glucopyranan (9). 相似文献
105.
Dr. Bishnu Prasad Bastakoti Prof. Kevin C.‐W. Wu Dr. Masamichi Inoue Prof. Shin‐ichi Yusa Prof. Kenichi Nakashima Prof. Yusuke Yamauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4812-4817
We have developed core‐shell‐corona‐type polymeric micelles that can integrate multiple functions in one system, including the capability of accommodating hydrophobic dyes into core and hydrophilic drug into the shell, as well as pH‐triggered drug‐release. The neutral and hydrophilic corona sterically stabilizes the multifunctional polymeric micelles in aqueous solution. The mineralization of calcium phosphate (CaP) on the PAA domain not only enhances the diagnostic efficacy of organic dyes, but also works as a diffusion barrier for the controlled release. 相似文献
106.
Dr. Yu Nakagawa Takashi Doi Takara Taketani Prof. K. Takegoshi Prof. Yasuhiro Igarashi Dr. Yukishige Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10516-10525
Pradimicins (PRMs) and benanomicins are the only family of non‐peptidic natural products with lectin‐like properties, that is, they recognize D ‐mannopyranoside (Man) in the presence of Ca2+ ions. Coupled with their unique Man binding ability, they exhibit antifungal and anti‐HIV activities through binding to Man‐containing glycans of pathogens. Notwithstanding the great potential of PRMs as the lectin mimics and therapeutic leads, their molecular basis of Man recognition has yet to be established. Their aggregate‐forming propensity has impeded conventional interaction analysis in solution, and the analytical difficulty is exacerbated by the existence of two Man binding sites in PRMs. In this work, we investigated the geometry of the primary Man binding of PRM‐A, an original member of PRMs, by the recently developed analytical strategy using the solid aggregate composed of the 1:1 complex of PRM‐A and Man. Evaluation of intermolecular distances by solid‐state NMR spectroscopy revealed that the C2–C4 region of Man is in close contact with the primary binding site of PRM‐A, while the C1 and C6 positions of Man are relatively distant. The binding geometry was further validated by co‐precipitation experiments using deoxy‐Man derivatives, leading to the proposal that PRM‐A binds not only to terminal Man residues at the non‐reducing end of glycans, but also to internal 6‐substituted Man residues. The present study provides new insights into the molecular basis of Man recognition and glycan specificity of PRM‐A. 相似文献
107.
Dr. Ryu Yamasaki Dr. Masato Ohashi Kyotaro Maeda Takuya Kitamura Minami Nakagawa Korehito Kato Tetsushi Fujita Ryohei Kamura Kazuto Kinoshita Dr. Hyuma Masu Prof. Dr. Isao Azumaya Prof. Dr. Sensuke Ogoshi Prof. Dr. Shinichi Saito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3415-3425
A detailed study of the Ni‐catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine‐membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes. 相似文献
108.
Miho Kusakari Yurie OhtaHideaki Nakagawa Hiroshi KatagiriTatsuro Kijima Satoshi MurakamiShigeru Matsuba Bunpei Hatano 《Tetrahedron letters》2014
An enantioresolution of 2-methoxy-2-(1-naphtyl)propionic acid (MαNP acid) using the diastereomeric salt with chiral (R)-phenylethylamine was achieved to give enantiopure (R)-MαNP acid in 29% yield with >99% ee based on rac-MαNP acid. X-ray crystallographic analysis of diastereomeric salt revealed that (R)-MαNP acid was tightly arranged by four independent hydrogen bonds and one CH–π interaction with (R)-phenylethylamine. 相似文献
109.
H. Kuboki H. Okuno A. Hershcovitch T. Dantsuka H. Hasebe K. Ikegami H. Imao O. Kamigaito M. Kase T. Maie T. Nakagawa Y. Yano 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1029-1034
A differential pumping system with a Plasma Window (PW) has been developed for an application to a window-less He gas charge stripper. A PW with Southern Methodist University design was newly fabricated and tested off-line for evaluation of differential pumping efficiency. Switching gases for plasma seed from Ar to He was tested. It was found that the PW reduced the pressure at the first differential pumping section to 1/13 for Ar and to 1/17 for He, comparing with differential pumping without PW. At the second pumping section, the pressures were drastically reduced to 1/160 and to 1/4,520 for Ar and He, respectively. These pressure reduction factors indicate that one differentially pumped stage could be removed from a conventional differential pumping system. 相似文献
110.
Keiichi Tomishige Masazumi Tamura Yoshinao Nakagawa 《Chemical record (New York, N.Y.)》2014,14(6):1041-1054
The catalytic performance of ReOx‐modified Ir metal catalyst in the hydrogenolysis of C–O bonds is strongly dependent on the choice of solvent. The acidic property of the Re species becomes obvious in the alkane solvent, and the hydrogenolysis reaction proceeds mainly by acid‐catalyzed dehydration and the subsequent metal‐catalyzed hydrogenation. The acidic property of the Re species is weakened in water; however, the hydrogenolysis reaction proceeds in water via a direct mechanism involving SN2‐like attack of a hydride species at the interface between Ir and ReOx on the adsorbed Re alkoxide species. This mechanism enabled the selective dissociation of the C–O bond neighboring the CH2OH group. 相似文献