PubMed:16442508 JSONTXT

{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":68},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":69,"end":219},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":220,"end":454},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":455,"end":639},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":640,"end":828},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":829,"end":1257},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":68},"obj":"Sentence"},{"id":"T2","span":{"begin":69,"end":219},"obj":"Sentence"},{"id":"T3","span":{"begin":220,"end":454},"obj":"Sentence"},{"id":"T4","span":{"begin":455,"end":639},"obj":"Sentence"},{"id":"T5","span":{"begin":640,"end":828},"obj":"Sentence"},{"id":"T6","span":{"begin":829,"end":1257},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Fluorinated acyclo-C-nucleoside analogues from glycals in two steps.\nA convenient two-step strategy is reported for the synthesis of fluorinated optically pure acyclo-C-nucleoside analogues starting from simple glycals. In the first step, benzyl- or p-methoxybenzyl-protected glycals are treated with trifluoroacetic anhydride, bromodifluoroacetyl chloride, trichloroacetyl chloride, and perfluorooctanoyl chloride, respectively, in the presence of Et3N. This one-pot procedure yields 1,2-unsaturated sugars (1,5-anhydro-3,4,6-tri-O-benzyl (or p-methoxybenzyl) 2-deoxy-2-perhalogenoacyl-D-arabino / lyxo-hex-1-enitols 4-9) acylated at C-2. In the second step, a selective ring transformation is induced by treatment of the C-acylated glycals with bis-nucleophiles (hydrazine, phenylhydrazine, o-phenylenediamine, hydroxylamine). In particular, 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-2-trifluoroacetyl-D-arabino-hex-1-enitol (4) and 1,5-anhydro-2-deoxy-2-trifluoroacetyl-3,4,6-tri-O-(p-methoxybenzyl)-D-arabino-hex-1-enitol (8) were reacted with these nucleophiles generating the final C-nucleoside analogues of pyrazole (10, 11, and 12), diazepine (13), and isoxazole (15), respectively, containing a carbohydrate side chain linked to the heterocyclic ring."}