摘要 :
A metal-free catalytic method for the synthesis of 2-deoxy glycosides and disaccharides has been developed using stable 2-deoxy glucosyl and galactosyl acetate donors. They could react with a variety of acceptors in the presence o...
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A metal-free catalytic method for the synthesis of 2-deoxy glycosides and disaccharides has been developed using stable 2-deoxy glucosyl and galactosyl acetate donors. They could react with a variety of acceptors in the presence of catalytic amount of TMSOTf at 0癈 to form glycosides, glycoconjugates, and disaccharides with excellent ?selectivity (> 19:1) and yields (up to 99%) in a short time (0.5 h). With this expedient method, several new compounds against human K562 and SMMC7721 cell lines were obtained and tested with in vitro antitumor bioactivities.
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摘要 :AbstractSynthesis of impurity reference compound of anti-tumor drug ISIS 183750 was achieved. In this process, a general method for synthesis of 2-deoxy ribosyl disaccharide nucleosides was established for the first time.Gra...
展开AbstractSynthesis of impurity reference compound of anti-tumor drug ISIS 183750 was achieved. In this process, a general method for synthesis of 2-deoxy ribosyl disaccharide nucleosides was established for the first time.Graphical abstractDisplay Omitted]]>
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The stereoselectivity of the reactions of D-glucal derivatives with PhSCl and PhSeCl is dependent on the presence of an electronegative heteroatom substituent at C(6) and the nature of the functionality at C(4). The C(6)-substitue...
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The stereoselectivity of the reactions of D-glucal derivatives with PhSCl and PhSeCl is dependent on the presence of an electronegative heteroatom substituent at C(6) and the nature of the functionality at C(4). The C(6)-substituent influences the conformational preferences of the D-glucal derivatives, and greatest stereoselectivity is obtained with those glycals that preferentially exist in the inverted H-5(4) half-chair conformation 28b. A polar substituent at C(4) increases the selectivity by stabilizing the episulfonium/episelenonium ion intermediates 31b and 33. (C) 1997 Elsevier Science Ltd. [References: 52]
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The Stereoselective synthesis of C-C linked deoxy disaccharides by a short and efficient route is described.An RCM strategy was adopted for the assembly of the required ring skeleton on the sugar unit,while OsO_4 was used to intro...
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The Stereoselective synthesis of C-C linked deoxy disaccharides by a short and efficient route is described.An RCM strategy was adopted for the assembly of the required ring skeleton on the sugar unit,while OsO_4 was used to introduce the vic-diol unit.
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A simple method for the preparation of O-unprotected methyl 2-deoxy-2-isothiocyanato-#alpha#-D-glucopyranoside 2 is described. This compound undergoes spontaneous intramolecular cyclization to give the trans-fused bicyclic oxazoli...
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A simple method for the preparation of O-unprotected methyl 2-deoxy-2-isothiocyanato-#alpha#-D-glucopyranoside 2 is described. This compound undergoes spontaneous intramolecular cyclization to give the trans-fused bicyclic oxazolidine-2-thione 3. A temperature-dependent equilibrium between 2 and 3 is observed. An efficient one-pot procedure for obtaining unprotected sugar thioureas is described.
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摘要 :AbstractGram-scale syntheses of two kinds of bleomycin disaccharides are described.l-gulose subunit12was accomplished with a novel and short route in six steps and 37% overall yield from4, which could be easily prepared from the c...
展开AbstractGram-scale syntheses of two kinds of bleomycin disaccharides are described.l-gulose subunit12was accomplished with a novel and short route in six steps and 37% overall yield from4, which could be easily prepared from the commercially available inexpensive materiald-sorbitol, while 6-deoxy-l-gulose subunit was synthesized in 11 steps in 8% yield fromd-glucolactone. The disaccharides were then prepared in a previously reported glycosidation coupling of the 3-O-carbamoyl-mannosyl donor with thel-gulopyranoside acceptors. Both disaccharides were finally obtained in gram-scale and the total synthesis of disaccharide2was achieved the first time.Graphical abstractDisplay Omitted]]>
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2-Deoxy-2-iodopyranosides 3, and 9-12 were synthesized from sulfanyl alkenes using a "one pot" consecutive cyclization-glycosylation process. Compared with the stepwise procedure, the "one pot" process gave significantly improved ...
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2-Deoxy-2-iodopyranosides 3, and 9-12 were synthesized from sulfanyl alkenes using a "one pot" consecutive cyclization-glycosylation process. Compared with the stepwise procedure, the "one pot" process gave significantly improved yields with similar or slightly lower selectivities. The "one pot" procedure was applied to the synthesis of 2,6-dideoxy-2-iodoglycoside 22, which was successfully deiodinated to afford the 2,6-dideoxyglycoside 23. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).
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Selective enzymatic hydrolysis of the peracetylated disaccharides, namely cellobiose, lactose, maltose and melibiose, with lipase from Asperilligus niger in aqueous buffer and organic solvent for 30 min afforded exclusively the co...
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Selective enzymatic hydrolysis of the peracetylated disaccharides, namely cellobiose, lactose, maltose and melibiose, with lipase from Asperilligus niger in aqueous buffer and organic solvent for 30 min afforded exclusively the corresponding heptaacetates with a free hydroxyl group at C-1 in high yield. Prolonged reaction of the #beta#-1,4 linked cellobiose and lactose peracetates afforded selectively their hexaacetates with free hydroxyl groups at C-1,2, whereas the #alpha#-1, 4 linked disaccharides maltose and melibiose peracetate gave a complex mixture of products. The reaction of 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetylglucopyranose (11) for 22 h afforded as the major product the diacetate 12 with free hydroxyl groups at C-1,4.
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Expeditious and stereocontrolled syntheses are reported of beta-D-Glc pNAc-(1 --> 4)-[beta-D-Glc pA-(1 --> 3)-beta-D-Glc pNAc-(1 --> 4)](n)-beta-D-Glc pA-(1 --> OMe), where n = 1, 2, and 3, which represent structural elements of t...
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Expeditious and stereocontrolled syntheses are reported of beta-D-Glc pNAc-(1 --> 4)-[beta-D-Glc pA-(1 --> 3)-beta-D-Glc pNAc-(1 --> 4)](n)-beta-D-Glc pA-(1 --> OMe), where n = 1, 2, and 3, which represent structural elements of the extracellular polysaccharide hyaluronic acid. Condensation of 4,6-O-benzylidene-3-O-chloroacetyl-2-deoxy-2-trichloroacetamide-alpha-D-gl ucopyranosyl trichloroacetimidate with methyl (4-methoxyphenyl 2,3-di-O-benzoyl-beta-D-glucopyranosid)uronate gave the disaccharide derivative 9, which was demethoxyphenylated and imidoylated to afford the pivotal disaccharide trichloroacetimidate 7. Condensation of 7 with methanol followed by O-dechloroacetylation gave the acceptor 8. Coupling of 7 with 8 gave the tetrasaccharide derivative 4. O-Dechloroacetylation of 4 followed by condensation with imidate 7 afforded hexasaccharide 5, which was transformed into octasaccharide 6 by a similar two-step procedure. Subsequent O-dechloroacetylation, transformation of the N-trichloroacetyl groups into N-acetyl, debenzylidenation, and saponification of 4-6 afforded the tetra- (1), hexa- (2), and octa-saccharide (3) derivatives in high yields, as their sodium salts. (C) 1996 Elsevier Science Ltd. [References: 33]
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As stable glycomimetics, thioglycosides are important tools for the investigation of biological processes and discovery of new drugs. In this note, we report a ReOCl3(SMe2)(OPPh3) catalyzed coupling reaction between beta-glycosyl ...
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As stable glycomimetics, thioglycosides are important tools for the investigation of biological processes and discovery of new drugs. In this note, we report a ReOCl3(SMe2)(OPPh3) catalyzed coupling reaction between beta-glycosyl thiols (1-thio sugars) and glycals for the preparation of 1,1'-alpha,13-2-deoxy thioglycosides, which are glycomimetics of natural trehalose and 2-deoxy glycosides. Furthermore, an S-linked trisaccharide was suc-cessfully obtained by successive employment of the Re(V) catalyzed thioglycosylation protocol.
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