PubMed:16199022
Annnotations
{"target":"https://pubannotation.org/docs/sourcedb/PubMed/sourceid/16199022","sourcedb":"PubMed","sourceid":"16199022","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/16199022","text":"Anomeric O-acylation of Kdo using alkyl and aryl isocyanates.\nTo develop a convenient method for the preparation of an alpha-Kdo derivative carrying a functional spacer at the reducing end, we examined anomeric O-acylation using Kdo and halogenated alkyl/aryl isocyanates as nucleophile and electrophiles, respectively. Reaction of a Kdo derivative with 2-chloroethyl isocyanate in the presence of DMAP gave an alpha-spiro product (82%) and an alpha-Kdo derivative of a dimeric isocyanate adduct (10%). Similar reaction with 4-(chloromethyl)phenyl isocyanate gave only the corresponding alpha-spiro product (81%). The NMR data show that the pyranose rings of both the alkyl and aryl spiro products adopt the 5C2 conformation. Thus, we accomplished alpha-selective anomeric O-acylation by coupling the Kdo derivative with alkyl and aryl isocyanates.","tracks":[{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":61},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":62,"end":319},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":320,"end":502},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":503,"end":613},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":614,"end":725},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":726,"end":848},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":61},"obj":"Sentence"},{"id":"T2","span":{"begin":62,"end":319},"obj":"Sentence"},{"id":"T3","span":{"begin":320,"end":502},"obj":"Sentence"},{"id":"T4","span":{"begin":503,"end":613},"obj":"Sentence"},{"id":"T5","span":{"begin":614,"end":725},"obj":"Sentence"},{"id":"T6","span":{"begin":726,"end":848},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"attributes":[{"subj":"TextSentencer_T1","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T2","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T3","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T4","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T5","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T6","pred":"source","obj":"sentences"},{"subj":"T1","pred":"source","obj":"sentences"},{"subj":"T2","pred":"source","obj":"sentences"},{"subj":"T3","pred":"source","obj":"sentences"},{"subj":"T4","pred":"source","obj":"sentences"},{"subj":"T5","pred":"source","obj":"sentences"},{"subj":"T6","pred":"source","obj":"sentences"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"sentences","color":"#93ecd8","default":true}]}]}}