PubMed:3690568 JSONTXT

{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":162},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":163,"end":436},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":437,"end":697},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":698,"end":828},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":829,"end":1045},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":1046,"end":1294},"obj":"Sentence"},{"id":"TextSentencer_T7","span":{"begin":1295,"end":1687},"obj":"Sentence"},{"id":"TextSentencer_T8","span":{"begin":1688,"end":1828},"obj":"Sentence"},{"id":"TextSentencer_T9","span":{"begin":1829,"end":2065},"obj":"Sentence"},{"id":"TextSentencer_T10","span":{"begin":2066,"end":2171},"obj":"Sentence"},{"id":"TextSentencer_T11","span":{"begin":2172,"end":2329},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":162},"obj":"Sentence"},{"id":"T2","span":{"begin":163,"end":436},"obj":"Sentence"},{"id":"T3","span":{"begin":437,"end":697},"obj":"Sentence"},{"id":"T4","span":{"begin":698,"end":828},"obj":"Sentence"},{"id":"T5","span":{"begin":829,"end":1045},"obj":"Sentence"},{"id":"T6","span":{"begin":1046,"end":1294},"obj":"Sentence"},{"id":"T7","span":{"begin":1295,"end":1687},"obj":"Sentence"},{"id":"T8","span":{"begin":1688,"end":1828},"obj":"Sentence"},{"id":"T9","span":{"begin":1829,"end":2065},"obj":"Sentence"},{"id":"T10","span":{"begin":2066,"end":2171},"obj":"Sentence"},{"id":"T11","span":{"begin":2172,"end":2329},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Alternative syntheses and related n.m.r. studies of precursors for internal beta-D-galactopyranosyl residues in oligosaccharides, allowing chain extension at O-4.\nCrystalline 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha-D-galactopyranosyl chloride (5) was prepared from methyl 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha- or -beta-D-galactopyranoside by cleavage with dichloromethyl methyl ether (DCMME) in the presence of zinc chloride. Silver trifluoromethanesulfonate (triflate) condensation of 5 with methyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside gave the corresponding beta-linked disaccharide, which was O-de(bromoacetyl)ated and the resulting disaccharide nucleophile condensed with 5. The beta-linked trisaccharide obtained was deprotected, to give the methyl beta-glycoside of (1----4)-beta-linked D-galactotriose. Compound 5 was converted in high yield into the corresponding 1-O-beta-acetyl derivative, which was O-de(bromoacetyl)ated with thiourea to afford crystalline 1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D-galactopyranose (9). Condensation of 9 with 5 yielded O-[2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-beta-D- galactopyranosyl]-(1----4)-1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D- galactopyranose (17), which was cleaved with DCMME to give the corresponding glycosyl chloride (20). The same sequence of reactions involving 1,2,3,6-tetra-O-benzoyl-alpha-D-galactopyranose and 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide afforded O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,3,6-tri-O - benzoyl-alpha-D-galactopyranosyl chloride, which can be used to construct in an oligosaccharide the terminal, beta-linked (1----4)-beta-D-galactobiosyl group. Compounds 5, 17, and 20, when used as glycosyl donors, allow further chain extension at O-4 of the (terminal) beta-D-galactopyranosyl group. The structures of all mono- and di-saccharide intermediates, including those of orthoesters formed during glycosylations under neutral conditions, were confirmed by combination of homo- and hetero-nuclear-correlation n.m.r. experiments. The sites of glycosidic linkages in orthoesters were directly determined by 1 D INAPT n.m.r. experiments. Characteristic features of the 1H- and 13C-n.m.r. spectra of orthoesters which distinguish them from the corresponding oligosaccharides have been summarized."}

{"project":"NCBITAXON","denotations":[{"id":"T1","span":{"begin":1344,"end":1351},"obj":"OrganismTaxon"},{"id":"T2","span":{"begin":1396,"end":1403},"obj":"OrganismTaxon"},{"id":"T3","span":{"begin":1465,"end":1472},"obj":"OrganismTaxon"},{"id":"T4","span":{"begin":2009,"end":2013},"obj":"OrganismTaxon"}],"attributes":[{"id":"A1","pred":"db_id","subj":"T1","obj":"100829"},{"id":"A2","pred":"db_id","subj":"T2","obj":"100829"},{"id":"A3","pred":"db_id","subj":"T3","obj":"100829"},{"id":"A4","pred":"db_id","subj":"T4","obj":"9605"}],"text":"Alternative syntheses and related n.m.r. studies of precursors for internal beta-D-galactopyranosyl residues in oligosaccharides, allowing chain extension at O-4.\nCrystalline 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha-D-galactopyranosyl chloride (5) was prepared from methyl 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha- or -beta-D-galactopyranoside by cleavage with dichloromethyl methyl ether (DCMME) in the presence of zinc chloride. Silver trifluoromethanesulfonate (triflate) condensation of 5 with methyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside gave the corresponding beta-linked disaccharide, which was O-de(bromoacetyl)ated and the resulting disaccharide nucleophile condensed with 5. The beta-linked trisaccharide obtained was deprotected, to give the methyl beta-glycoside of (1----4)-beta-linked D-galactotriose. Compound 5 was converted in high yield into the corresponding 1-O-beta-acetyl derivative, which was O-de(bromoacetyl)ated with thiourea to afford crystalline 1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D-galactopyranose (9). Condensation of 9 with 5 yielded O-[2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-beta-D- galactopyranosyl]-(1----4)-1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D- galactopyranose (17), which was cleaved with DCMME to give the corresponding glycosyl chloride (20). The same sequence of reactions involving 1,2,3,6-tetra-O-benzoyl-alpha-D-galactopyranose and 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide afforded O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,3,6-tri-O - benzoyl-alpha-D-galactopyranosyl chloride, which can be used to construct in an oligosaccharide the terminal, beta-linked (1----4)-beta-D-galactobiosyl group. Compounds 5, 17, and 20, when used as glycosyl donors, allow further chain extension at O-4 of the (terminal) beta-D-galactopyranosyl group. The structures of all mono- and di-saccharide intermediates, including those of orthoesters formed during glycosylations under neutral conditions, were confirmed by combination of homo- and hetero-nuclear-correlation n.m.r. experiments. The sites of glycosidic linkages in orthoesters were directly determined by 1 D INAPT n.m.r. experiments. Characteristic features of the 1H- and 13C-n.m.r. spectra of orthoesters which distinguish them from the corresponding oligosaccharides have been summarized."}

{"project":"Anatomy-UBERON","denotations":[{"id":"T1","span":{"begin":145,"end":154},"obj":"Body_part"},{"id":"T2","span":{"begin":1763,"end":1772},"obj":"Body_part"}],"attributes":[{"id":"A1","pred":"uberon_id","subj":"T1","obj":"http://purl.obolibrary.org/obo/UBERON_2000106"},{"id":"A2","pred":"uberon_id","subj":"T2","obj":"http://purl.obolibrary.org/obo/UBERON_2000106"}],"text":"Alternative syntheses and related n.m.r. studies of precursors for internal beta-D-galactopyranosyl residues in oligosaccharides, allowing chain extension at O-4.\nCrystalline 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha-D-galactopyranosyl chloride (5) was prepared from methyl 2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-alpha- or -beta-D-galactopyranoside by cleavage with dichloromethyl methyl ether (DCMME) in the presence of zinc chloride. Silver trifluoromethanesulfonate (triflate) condensation of 5 with methyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside gave the corresponding beta-linked disaccharide, which was O-de(bromoacetyl)ated and the resulting disaccharide nucleophile condensed with 5. The beta-linked trisaccharide obtained was deprotected, to give the methyl beta-glycoside of (1----4)-beta-linked D-galactotriose. Compound 5 was converted in high yield into the corresponding 1-O-beta-acetyl derivative, which was O-de(bromoacetyl)ated with thiourea to afford crystalline 1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D-galactopyranose (9). Condensation of 9 with 5 yielded O-[2,3,6-tri-O-benzoyl-4-O-(bromoacetyl)-beta-D- galactopyranosyl]-(1----4)-1-O-acetyl-2,3,6-tri-O-benzoyl-beta-D- galactopyranose (17), which was cleaved with DCMME to give the corresponding glycosyl chloride (20). The same sequence of reactions involving 1,2,3,6-tetra-O-benzoyl-alpha-D-galactopyranose and 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide afforded O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,3,6-tri-O - benzoyl-alpha-D-galactopyranosyl chloride, which can be used to construct in an oligosaccharide the terminal, beta-linked (1----4)-beta-D-galactobiosyl group. Compounds 5, 17, and 20, when used as glycosyl donors, allow further chain extension at O-4 of the (terminal) beta-D-galactopyranosyl group. The structures of all mono- and di-saccharide intermediates, including those of orthoesters formed during glycosylations under neutral conditions, were confirmed by combination of homo- and hetero-nuclear-correlation n.m.r. experiments. The sites of glycosidic linkages in orthoesters were directly determined by 1 D INAPT n.m.r. experiments. Characteristic features of the 1H- and 13C-n.m.r. spectra of orthoesters which distinguish them from the corresponding oligosaccharides have been summarized."}