RESUMEN
An efficient synthesis of 4-methoxyphenyl alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-6-deoxy-alpha-L-Talp, the tetrasaccharide related to the GPLs of Mycobacterium intracellare serotype 7, was achieved with 4-methoxyphenyl 3,4-di-O-benzoyl-6-deoxy-alpha-L-talopyranoside (6c) as the key intermediate which was obtained through selective 3-O-benzoylation of 4-O-benzoyl-6-deoxy-alpha-L-taloside. Coupling of 6c with 3-O-allyloxycarbonyl-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate followed by removal of the allyloxycarbonyl protecting group afforded the disaccharide acceptor 11. Condensation of 11 with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate and subsequent deprotection gave the target tetrasaccharide.
Asunto(s)
Desoxiazúcares/química , Glucolípidos/química , Hexosas/química , Complejo Mycobacterium avium/química , Oligosacáridos/síntesis química , Acilación , Secuencia de Carbohidratos , Datos de Secuencia Molecular , Oligosacáridos/química , Especificidad por SustratoRESUMEN
1-O-Allyloxycarbonyl (or ethyloxycarbonyl)-2-azido-2-deoxy-3-O-benzyl (or allyl, or benzoyl)-4,6-O-isopropylidene-beta-d-mannopyranose derivatives were prepared from the corresponding 2-hydroxy-beta-d-glucopyranosyl carbonates in high yields via triflation of the 2-hydroxyl group and subsequent SN2 displacement with azide ion. An N-acetyl-mannosamine-containing trisaccharide, a fragment of the putative O10 antigen from Acinetobacter baumannii, was efficiently synthesized using these derivatives.
Asunto(s)
Carbonatos/química , Carbonatos/síntesis química , Manosa/análogos & derivados , Manosa/química , Trisacáridos/química , Trisacáridos/síntesis química , Acinetobacter baumannii/química , Secuencia de Carbohidratos , Hexosaminas/química , Datos de Secuencia Molecular , Antígenos O/químicaRESUMEN
A highly regio- and stereoselective anomeric esterification of 3-O-allyl (or benzyl, or benzoyl)-4,6-O-isopropylidene-alpha,beta-d-glucopyranose with acetyl chloride, or allyl chloroformate, or ethyl chloroformate gave the corresponding 2-OH, 1-beta-acetates or -carbonates in excellent yields. The 2-OH, 1-beta-acetates were readily converted to the corresponding 2-O-acetylated glucopyranosyl trichloroacetimidates by reaction with trichloroacetonitrile via base promoted acetyl migration, while the 2-OH, 1-beta-carbonates were good glycosyl acceptors for the synthesis of (1-->2)-linked oligosaccharides.
Asunto(s)
Acetonitrilos/química , Oligosacáridos/química , Oligosacáridos/síntesis química , Acetatos/química , Conformación de Carbohidratos , Cloruros/química , Esterificación , Formiatos/química , Ésteres del Ácido Fórmico/química , Modelos Químicos , Estructura Molecular , EstereoisomerismoRESUMEN
Formation of sugar-sugar orthoesters consisting of a fully acylated mono- or disaccharide donor and a partially protected mono- or disaccharide acceptor is regioselective, and rearrangement of the orthoesters via RO-(orthoester)C bond cleavage gives a dioxolenium ion intermediate leading to 1,2-trans glycosidic linkage. The activity order of hydroxyl groups in the partially protected mannose and glucose acceptors is 6-OH>3-OH>2- or 4-OH. The coupling reactions with acylated glycosyl trichloroacetimidates as the donors usually give orthoesters as the intermediates specially when the coupling is carried out at slowed rates, and this is successfully used in regio- and stereoselective syntheses of oligosaccharides. Mannose and rhamnose orthoesters readily undergo O-2-(orthoester)C bond breaking, and this is used for synthesis of alpha-(1-->2)-linked oligosaccharides. (1-->3)-Glucosylation is special since the rearrangement of its sugar orthoester intermediates can occur with either RO-(orthoester)C bond cleavage with formation of the dioxolenium ion leading to 1,2-trans linkage, or C-1-O-1 bond cleavage leading to 1,2-cis linkage, and this is dependent upon the structures of donor and acceptor that compose the orthoester.
Asunto(s)
Oligosacáridos/síntesis química , Secuencia de Carbohidratos , Ésteres/química , Glucosa/análogos & derivados , Glucosa/química , Lentinano/síntesis química , Manosa/análogos & derivados , Manosa/química , Datos de Secuencia Molecular , Oligosacáridos de Cadena Ramificada/síntesis química , Ramnosa/análogos & derivados , Ramnosa/químicaRESUMEN
A concise and practical synthesis of the antigenic globotriose, alpha-D-Gal-(1-->4)-beta-D-Gal-(1-->4)-beta-D-Glc (13), was achieved by coupling of a monosaccharide donor, 3-O-allyl-2-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranosyl trichloroacetimidate (4) with a disaccharide acceptor, p-methoxyphenyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzoyl-beta-D-glucopyranoside (8), followed by deprotection. In spite of the existence of a C-2-ester substituent capable of neighboring-group participation in the donor, the coupling gave exclusively the alpha-linkage in satisfactory yield. The acceptor 8 was readily obtained from selective 3-O-benzoylation of the galactosyl ring of p-methoxyphenyl 2,6-di-O-benzoyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzoyl-beta-D-glucopyranoside (7), which was prepared from p-methoxyphenyl beta-D-lactoside (5) via isopropylidenation, benzoylation, and deisopropylidenation. Donor 4 was obtained from p-methoxylphenyl 3-O-allyl-2,4,6-tri-O-benzoyl-beta-D-galactopyranoside (1) via selective 4,6-di-O-debenzoylation, oxidative removal of 1-O-MP, benzylidenation, and trichloroacetimidate formation.
Asunto(s)
Antígenos/química , Trisacáridos/síntesis química , Animales , Secuencia de Carbohidratos , Humanos , Datos de Secuencia Molecular , Trisacáridos/inmunologíaRESUMEN
Effective syntheses of galactose hepta-, octa-, nona-, and decasaccharides that exist in the rhizomes of Atractylodes lancea DC were achieved with 2,3,4,6-tetra-O-benzoyl-alpha-d-galactopyranosyl trichloroacetimidate (1), 4-methoxyphenyl 2,3,4-tri-O-benzoyl-beta-d-galactopyranoside (2), 6-O-acetyl-2,3,4-tri-O-benzoyl-alpha-d-galactopyranosyl trichloroacetimidate (5), 4-methoxyphenyl 6-O-acetyl-2,4-di-O-benzoyl-beta-d-galactopyranoside (22), and 4-methoxyphenyl 2,4,6-tri-O-benzoyl-beta-d-galactopyranoside (26) as the key synthons. Coupling of 2 with 1, followed by oxidative cleavage of 1-OMP and subsequent trichloroacetimidate formation gave the beta-(1-->6)-linked disaccharide donor 4. Condensation of 2 with 5 and subsequent selective deacetylation by methanolysis produced the beta-(1-->6)-linked disaccharide acceptor 7. Reaction of 7 with 4, oxidative cleavage of 1-OMP, and trichloroacetimidate formation produced the tetrasaccharide donor 9. The penta- (15), the hexa- (17), and the heptasaccharide donor 19 were synthesized similarly. Meanwhile, treatment of 1 with 22 yielded beta-(1-->3)-linked disaccharide 23 and alpha-(1-->3)-linked disaccharide 25. Oxidative cleavage of 1-OMp of 23 followed by trichloroacetimidate formation produced the disaccharide donor 24. Coupling of 26 with 24, again, gave beta-linked 27 and alpha-linked 29. Selective 6-O-deacetylation of 27 afforded the trisaccharide acceptor 28. TMSOTf-promoted condensation 28 of with the tetra- (9), penta- (15), hexa-(17), and heptasaccharide donor 19, followed by deprotection, gave the target compounds.
Asunto(s)
Atractylodes/química , Galactanos/síntesis química , Oligosacáridos de Cadena Ramificada/síntesis química , Adyuvantes Inmunológicos/síntesis química , Conformación de Carbohidratos , Secuencia de Carbohidratos , Galactanos/química , Datos de Secuencia Molecular , Rizoma/químicaRESUMEN
Beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->4)]-alpha-D-Manp, the fragment of the exopolysaccharide from Cryptococcus neoformans serovar C, was synthesized as its methyl glycoside. Thus, chloroacetylation of allyl 3-O-acetyl-4,6-O-benzylidene-alpha-D-mannopyranoside (1) followed by debenzylidenation and selective 6-O-benzoylation afforded allyl 2-O-chloroacetyl-3-O-acetyl-6-O-benzoyl-alpha-D-mannopyranoside (4). Glycosylation of 4 with 2,3,4-tri-O-benzoyl-D-xylopyranosyl trichloroacetimidate (5) furnished the beta-(1-->4)-linked disaccharide 6. Dechloroacetylation gave the disaccharide acceptor 7 and subsequent coupling with 5 produced the trisaccharide 8. Deacetylation of 8 gave the trisaccharide acceptor 9 and subsequent coupling with a disaccharide 10 produced the pentasaccharide 11. Reiteration of deallylation and trichloroacetimidate formation from 11 yielded the pentasaccharide donor 12. Coupling of a disaccharide acceptor 13 with 12 afforded the heptasaccharide 14. Subsequent deprotection gave the heptaoside 16, while selective 2-O-deacetylation of 14 gave the heptasaccharide acceptor 15. Condensation of 15 with glucopyranosyluronate imidate 17 did not yield the expected octaoside, instead, an orthoester product 18 was obtained. Rearrangement of 18 did not give the target octaoside; but produced 15. Meanwhile, there was no reaction between 15 and the glycosyl bromide donor 19.
Asunto(s)
Cryptococcus neoformans/química , Cryptococcus neoformans/clasificación , Polisacáridos Bacterianos/química , Acetilación , Secuencia de Carbohidratos , Polisacáridos , SerotipificaciónRESUMEN
4-methoxyphenyl glycosides of 2,3''-bis-alpha-L-arabinofuranosyl branched beta-D-(1-->6)-linked galactopyranosyl tetraose (16), 3',2''''-bis-alpha-L-arabinofuranosyl branched beta-D-(1-->6)-linked galactopyranosyl hexaose (27), and a twentyose (42) consisting of beta-(1-->6)-linked D-galactopyranosyl pentadecaoligosaccharide backbone with alpha-L-arabinofuranosyl side chains alternately attached at C-2 and C-3 of the middle galactose residue of each consecutive beta-(1-->6)-linked galactotriose unit of the backbone, were synthesized with isopropyl 3-O-allyl-2,4-di-O-benzoyl-1-thio-beta-D-galactopyranoside (6), 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (7), 2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosyl trichloroacetimidate (12), 6-O-acetyl-2,3,4-tri-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (17), 4-methoxyphenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (19), and 2,6-di-O-acetyl-3,4-di-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (28) as the key synthons. Condensation of 6 with 7 gave the disaccharide donor 8, and subsequent condensation of 8 with 4-methoxyphenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranosyl-(1-->6)-2-O-acetyl-3,4-di-O-benzoyl-beta-D-galactopyranoside (9) followed by selective deacetylation afforded the tetrasaccharide acceptor 11. Coupling of 11 with 12 gave the pentasaccharide 13, its deallylation followed by coupling with 12, and debenzoylation gave the hexasaccharide 16 with beta-(1-->6)-linked galactopyranose backbone and 2- and 3''-linked alpha-L-arabinofuranose side chains. The octasaccharide 27 was similarly synthesized, while the twentyoside 42 was synthesized with tetrasaccharides 33 or 24 as the donors and 23, 36, 38, and 40 as the acceptors by consecutive couplings followed by deacylation.
Asunto(s)
Arabinosa/análogos & derivados , Arabinosa/química , Galactanos/síntesis química , Galactosa/química , Secuencia de Carbohidratos , Espectroscopía de Resonancia Magnética , Datos de Secuencia MolecularRESUMEN
The allyl glycoside beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-alpha-D-Glcp (18) and the acetonyl glycoside of beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-alpha-D-Glcp (28) were synthesized as analogues of the lentinan heptaose repeating unit. 4,6-O-Benzylidenated monosaccharide donor 3 and 4,6-O-benzylidenated tetrasaccharide acceptor 14 were used to ensure the beta-linkage in the synthesis of 18, while 4,6-O-benzylidenated disaccharide acceptor 20, and 4,6-O-benzylidenated disaccharide donors 21 and 24 were used to ensure the beta-linkage in the synthesis of 28.
Asunto(s)
Lentinano/química , Polisacáridos/química , Polisacáridos/síntesis química , Secuencia de Carbohidratos , Lentinano/análogos & derivados , Datos de Secuencia Molecular , Estructura Molecular , Oligosacáridos de Cadena Ramificada/síntesis química , Oligosacáridos de Cadena Ramificada/químicaRESUMEN
A heptasaccharide, beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar B, was synthesized as its methyl glycoside. Thus 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-d-mannopyranosyl trichloroacetimidate (7) and allyl 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-4,6-di-O-benzoyl-alpha-D-mannopyranoside (8), readily obtained from the corresponding monosaccharide derivatives via simple transformation, were coupled to give a (1-->3)-linked tetrasaccharide 9. Deallylation of 9 followed by trichloroacetimidate formation produced the tetrasaccharide donor 11. Condensation of methyl 2,3,4-tri-O-benzoyl-beta-d-xylopyranosyl-(1-->4)-2-O-acetyl-6-O-benzoyl-alpha-D-mannopyranoside (18) with 11 followed by selective deacetylation yielded hexasaccharide acceptor 20. Coupling of 20 with methyl 2,3,4-tri-O-acetyl-alpha-D-glucopyranosyluronate bromide (21) and subsequent deprotection furnished the target heptaoside. A hexasaccharide fragment, alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-GlcpA-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp, was also similarly synthesized as its methyl glycoside.
Asunto(s)
Cryptococcus neoformans/química , Oligosacáridos/síntesis química , Acetilación , Secuencia de Carbohidratos , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Oligosacáridos/químicaRESUMEN
Hexaose, beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-alpha-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp, based dimers were synthesized by twofold glycosidation of the hexaosyl trichloroacetimidate with hexylene 1,6-diol, diethylene glycol and triethylene glycol, respectively. Meanwhile, a triose, beta-1D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp, based trimer was obtained by glycosidation of the triosyl trichloroacetimidate with a glycerol-derived triol scaffold.
Asunto(s)
Glucosa/análogos & derivados , Glucosa/síntesis química , Oligosacáridos/síntesis química , Conformación de Carbohidratos , Secuencia de Carbohidratos , Glicosilación , Datos de Secuencia Molecular , Oligosacáridos/químicaRESUMEN
A hexasaccharide, beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->2)]-alpha-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->2)]-D-Glcp, the alpha-linked dimer of the trisaccharide repeating unit of the exopolysaccharide produced by Pediococcus damnosus 2.6, was synthesized as its methyl glycoside. Condensation of fully benzoylated alpha-D-glucopyranosyl trichloroacetimidate (1) with isopropyl 4,6-O-benzylidene-1-thio-beta-D-glucopyranoside (2) selectively furnished (1-->3)-linked disaccharide 3, and subsequent 2-O-acetylation, desulfation, and trichloroacetimidate formation afforded the disaccharide donor 6. Meanwhile, selective 3-O-coupling of methyl 4,6-O-benzylidene-alpha-d-glucopyranoside (8) with 3-O-allyl-2,4,6-tri-O-benzoyl-alpha-D-glucopyranosyl trichloroacetimidate (7), followed by coupling with 1 gave the trisaccharide 10. Removal of the benzylidene group of 10, benzoylation, and deallylation produced the trisaccharide acceptor 12. Condensation of 12 with 6 yielded a pentasaccharide mixture 13 with beta and alpha isomers in a ratio of 2:1. Removal of the benzylidene group of 13, followed by benzoylation gave the pentasaccharide mixture 14. Selective 2'''-deacetylation of the isolated beta-linked 14beta with MeCOCl/MeOH/CH2Cl2 did not give the expected pentasaccharide acceptor, and serious decomposition occurred, indicating a large steric hindrance at C-2'''. Alternatively, 2,3-di-O-glycosylation of allyl 4,6-O-benzylidene-beta-D-glucopyranoside (21) with 1 gave 22, then deallylation and trichloroacetimidate formation afforded the trisaccharide donor 24. Condensation of 12 with 24 furnished only the alpha-linked hexasaccharide 25, and its deprotection gave the free hexaoside 27.
Asunto(s)
Oligosacáridos/síntesis química , Pediococcus/química , Polisacáridos Bacterianos/química , Conformación de Carbohidratos , Secuencia de Carbohidratos , Dimerización , Glucosa , Trisacáridos/químicaRESUMEN
Two arabinogalactosyl nonasaccharides, beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->3)]-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->5)-alpha-L-Araf-(1-->3)]-beta-D-Galp-(1-->6)-beta-D-Galp and beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->5)-alpha-L-Araf-(1-->3)]-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->3)]-beta-D-Galp-(1-->6)-beta-D-Galp, were synthesized as their 4-methoxyphenyl glycosides with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (1), 6-O-acetyl-2,3,4-tri-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (14), 4-methoxyphenyl 3-O-allyl-2,4-di-O-benzoyl-beta-D-galactopyranoside (2), 4-methoxyphenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (5), 2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosyl trichloroacetimidate (8), and 2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosyl-(1-->5)-2,3-di-O-benzoyl-alpha-L-arabinofuranosyl trichloroacetimidate (11), as the key synthons. The tetra- (10) and pentasaccharide donor (13), and the tetra- (20) and pentasaccharide acceptor (22) were synthesized based on these synthons through simple transformations. Coupling of 22 with 10, and coupling of 20 with 13 and subsequent deacylation gave nonasaccharides 24 and 26, respectively, consisting of beta-(1-->6)-linked glactopyranosyl backbone and alpha-(1-->3)-linked arabinofuranosyl side chains of different size.
Asunto(s)
Arabinofuranosil Uracilo/química , Galactanos/síntesis química , Galactosa/química , Arabinofuranosil Uracilo/análogos & derivados , Conformación de Carbohidratos , Secuencia de Carbohidratos , Galactosa/análogos & derivados , Glicosilación , Datos de Secuencia MolecularRESUMEN
Syntheses of a hexasaccharide, the dimer of the repeating unit of the group E streptococci polysaccharide, and a tetrasaccharide, the repeating unit of the E. coli O7:K98:H6, were achieved by constructing alternate alpha-L-(1-->2)- and alpha-L-(1-->3)-linked L-rhamnopyranose backbones and substituting with beta-linked D-glucopyranose side chains for the former, and a D-glucopyranosyluronate branch for the latter, respectively, at O-2 of the L-rhamnose ring.
Asunto(s)
Escherichia coli/química , Oligosacáridos/síntesis química , Streptococcus/química , Streptococcus/clasificación , Secuencia de Carbohidratos , Glucanos/química , Glucuronatos/química , Datos de Secuencia Molecular , Oligosacáridos/química , Ramnosa/químicaRESUMEN
Pentasaccharide repeating unit 20 of the lipoarabinomannan from the equine pathogen, Rhodococcus equi, and its dimer 31, were synthesized. The pentasaccharide was obtained by assembling a benzoylated 2,6-branched mannosyl trisaccharide acceptor 13 with a free hydroxyl group at C-2' of the mannose residue attached to the core mannose residue by (1 --> 6)-linkage, followed by coupling with 2,3,5-tri-O-benzoyl-alpha-D-arabinofuranosyl-(1 --> 2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (18), and by deacylation. Meanwhile, the decamer 31 was obtained by firstly preparing a benzoylated mannose (1 --> 6)-linked tetrasaccharide backbone 26 with 2-, 2"-O-ClAc, and 2'-, 2'''-O-Ac groups, respectively, then by dechloroacetylation and subsequent condensation with perbenzoylated trichloroacetimidate, and then by deacetylation and subsequent coupling with 18, and finally, by deacylation.
Asunto(s)
Cloroacetatos , Lipopolisacáridos/química , Mananos/síntesis química , Polisacáridos/química , Rhodococcus equi/metabolismo , Acetamidas , Animales , Secuencia de Carbohidratos , Glicosilación , Caballos/microbiología , Espectroscopía de Resonancia Magnética , Mananos/química , Manosa/química , Modelos Químicos , Datos de Secuencia Molecular , Estereoisomerismo , Ácido Tricloroacético/químicaRESUMEN
beta-D-Xylp-(1-->4)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-alpha-D-Manp, the fragment of the exopolysaccharide from Cryptococcus neoformans serovar B, was synthesized as its methyl glycoside. Thus, acetylation of allyl 3-O-benzoyl-4,6-O-benzylidene-alpha-D-mannopyranoside (1) followed by debenzylidenation and selective 6-O-benzoylation afforded allyl 2-O-acetyl-3,6-di-O-benzoyl-alpha-D-mannopyranoside (4). Glycosylation of 4 with 2,3,4-tri-O-benzoyl-D-xylopyranosyl trichloroacetimidate (5) furnished the beta-(1-->4)-linked disaccharide 6. Deallylation followed by trichloroacetimidate formation gave the disaccharide donor 8, and subsequent coupling with allyl 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-4,6-di-O-benzoyl-alpha-D-mannopyranoside (9), produced the tetrasaccharide 10. Reiteration of deallylation and trichloroacetimidate formation from 10 yielded the tetrasaccharide donor 12. The downstream disaccharide acceptor 18 was obtained by condensation of 5 with methyl 3-O-acetyl-4,6-O-benzylidene-alpha-D-mannopyranoside, followed by debenzylidenation, benzoylation, and selective 3-O-deacetylation. Coupling of 18 with 12 afforded the hexasaccharide 19, and subsequent deprotection gave the hexasaccharide glycoside 20. Selective 2"-O-deacetylation of 19 gave the hexasaccharide acceptor 21. Condensation of 21 with glucopyranosyluronate imidate 22 did not produce the expected heptasaccharide glycoside; instead, a transacetylation product 19 was obtained. Meanwhile, there was no reaction between 21 and the bromide donor 23.
Asunto(s)
Cloroacetatos , Ácido Glucurónico/química , Manosa/química , Polisacáridos/química , Xilosa/química , Acetamidas , Acetilación , Bromuros/química , Secuencia de Carbohidratos , Cryptococcus neoformans/metabolismo , Glicósidos/química , Modelos Químicos , Datos de Secuencia Molecular , Piranos/química , Temperatura , Ácido Tricloroacético/químicaRESUMEN
An octasaccharide, beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->2)]-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->5)-alpha-L-Araf-(1-->2)]-beta-D-Galp-(1-->6)-beta-D-Galp-1-->OMP was synthesized. 4-methoxyphenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (5), 2,6-di-O-acetyl-3,4-di-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (9), and 4-methoxyphenyl 2-O-acetyl-3,4-di-O-benzoyl-beta-D-galactopyranoside (11), 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (12), and 2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosyl trichloroacetimidate (17) were used as the synthons. A concise route was used to gain the tetrasaccharide donor 19 by the use of 11, 12, 5, and 17. Meanwhile, treatment of 5 with 9 yielded beta-(1-->6)-linked disaccharide 20, and subsequent selective 6-O-deacetylation produced the disaccharide acceptor 21. Reaction of 21 with 19 gave 22, and subsequent selective 2-O-deacetylation afforded the hexasaccharide acceptor 23. Condensation of 23 with alpha-L-(1-->5)-linked arabinofuranose disaccharide 24, followed by deprotection, yielded the target octasaccharide.
Asunto(s)
Arabinosa/análogos & derivados , Arabinosa/química , Galactanos/química , Galactanos/síntesis química , Galactosa/química , Secuencia de Carbohidratos , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Estructura MolecularRESUMEN
Two oligosaccharides, alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp-(1-->4)-alpha-D-GlcpNAc (I) and alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp-(1-->4)-alpha-D-GlcpNAc (II), the glycosylphosphatidylinositol (GPI) anchor glycans from S. cerevesiae and A. fumigatus were synthesized as their methyl glycosides in a regio- and stereoselective manner. The pentasaccharide I was obtained from 6-O-selective glycosylation of methyl 2,3-di-O-benzoyl-alpha-D-mannopyranosyl-(1-->4)-2-acetamido-3,6-di-O-benzoyl-2-deoxy-alpha-D-glucopyranoside (8) with 2-O-acetyl-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (9), followed by benzoylation, deacetylation, and mannosylation, and then by deprotection. The hexasaccharide (II) was obtained via condensation of allyl 3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranoside (17) with 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-alpha-D-mannopyranosyl trichloroacetimidate (16), followed by deallylation, trichloroacetimidation, and coupling with acceptor (8), and finally by deprotection.
Asunto(s)
Aspergillus fumigatus/química , Glicosilfosfatidilinositoles/química , Oligosacáridos/síntesis química , Polisacáridos/química , Saccharomyces cerevisiae/química , Acetilación , Compuestos Alílicos/química , Conformación de Carbohidratos , Secuencia de Carbohidratos , Glicósidos/química , Glicosilación , Manosa/química , Datos de Secuencia MolecularRESUMEN
A concise synthesis of two isomeric pentasaccharides, alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-[beta-D-GlcpNAc-(1-->2)]-alpha-L-Rhap (A) and alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->3)-[beta-D-GlcpNAc-(1-->2)]-alpha-L-Rhap-(1-->3)-alpha-L-Rhap (B), the O repeats from the lipopolysaccharides of Pseudonomonas syringae pv. porri NCPPB 3364T and 3365 was achieved via assembly of the building blocks, allyl 3,4-di-O-benzoyl-alpha-L-rhamnopyranoside (1), 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (2), allyl 4-O-benzoyl-3-O-chloroacetyl-alpha-L-rhamnopyranoside (6), 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate (7), and allyl 2,4-di-O-benzoyl-alpha-L-rhamnopyranoside (10). Coupling of 1 with 2 followed by deallylation and trichloroacetimidate formation gave the disaccharide donor 5, while condensation of 6 with 7, followed by dechloroacetylation, offered the disaccharide acceptor 9. Then, 5 was coupled with 10 to obtain the trisaccharide 11, and subsequent deallylation and trichloroacetimidate formation furnished the trisaccharide donor 13. Coupling of 9 with 13, followed by deprotection, afforded pentasaccharide 19, while condensation of 9 with 5, followed by deallylation and trichloroacetimidate formation, gave the tetrasaccharide donor 16, whose coupling with 10 and subsequent deprotection yielded another pentasaccharide 22.
Asunto(s)
Lipopolisacáridos/síntesis química , Oligosacáridos/síntesis química , Pseudomonas syringae/química , Secuencia de Carbohidratos , Glicosilación , Isomerismo , Datos de Secuencia Molecular , Estructura Molecular , Ramnosa/química , Ácido Tricloroacético/químicaRESUMEN
Coupling of the trisaccharide acceptor 2,4,6-tri-O-acetyl-beta-D-glucopyranosyl-(1-->3)-[2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->6)]-5-O-acetyl-1,2-O-isopropylidene-alpha-D-glucofuranose (2) with the trisaccharide donor 2,3,4,6-tetra-O-benzoyl-alpha-D-annopyranosyl-(1-->3)-[2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->6)]-2,4-di-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (1) gave an alpha-linked hexasaccharide 3, while coupling of 2 with the trisaccharide donor 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-[2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->6)]-2,4-di-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (7) produced alpha- 8 and beta-linked 12 hexasaccharides in a ratio of 3:2. Deprotection of 3, 8, and 12 afforded the analogues of the immunomodulator beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-alpha-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-D-Glcp (A).