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Titolo:
Stereocontrolled synthesis and reactivity of sugar acetylenes
Autore:
Isobe, M; Nishizawa, R; Hosokawa, S; Nishikawa, T;
Indirizzi:
Nagoya Univ, Sch Bioagr Sci, Organ Chem Lab, Nagoya, Aichi 4648601, Japan Nagoya Univ Nagoya Aichi Japan 4648601 Lab, Nagoya, Aichi 4648601, Japan
Titolo Testata:
CHEMICAL COMMUNICATIONS
fascicolo: 24, , anno: 1998,
pagine: 2665 - 2676
SICI:
1359-7345(199812):24<2665:SSAROS>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
HETEROCONJUGATE ADDITION; ALLYLTRIMETHYLSILANE; SILYLACETYLENES; (+)-TAUTOMYCIN; CIGUATOXIN; COMPLEXES; FRAGMENT; GLUCALS; RING;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
44
Recensione:
Indirizzi per estratti:
Indirizzo: Isobe, M Nagoya Univ, Sch Bioagr Sci, Organ Chem Lab, Nagoya, Aichi 4648601, Japan Nagoya Univ Nagoya Aichi Japan 4648601 oya, Aichi 4648601, Japan
Citazione:
M. Isobe et al., "Stereocontrolled synthesis and reactivity of sugar acetylenes", CHEM COMMUN, (24), 1998, pp. 2665-2676

Abstract

C-Glycosidation is of great significance in the organic synthesis of optically active materials, since it allows the introduction of carbon chains tosugar chirons and the use of sugar nuclei as a chiral pool as well as a carbon source, Silylacetylenes are sufficiently reactive to form 'sugar acetylenes' for the selective introduction of various acetylenic groups in an alpha-axial manner at the anomeric position of D-hexopyranose rings, 1,4-Antiinduction, on the other hand, gives a different stereochemical outcome in the case of C-glycosidation of pentopyranose glycals, The mechanism of these reactions includes oxonium cation intermediates in which stereoelectronicand/or steric factors drive the direction of the incoming silylacetylene. Bis-C-glycosidation allows the introduction of sugars at both ends of some bis(trimethylsilyl)acetylenes. A 2,3-dideoxyglucose derivative provides thecorresponding C-1 a-acetylenic compounds, which would increase the scope of C-glycosidation with silylacetylenes. In sugar acetylenes, the alkynyl group at the anomeric position of a pyranose ring is epimerized via a hexacarbonyldicobalt complex by treatment with trifluoromethanesulfonic acid. The three steps-cobalt complexation, acidic transformation and decomplexation-afford overall epimerization and thus one can obtain either the alpha- or beta-alkynyl C-glycoside as desired. Ring opening of a dihydropyran derivative using Nicholas-type cation intermediates is also part of this study. Several sets of decomplexation conditions for endo-type acetylene-cobalt complexes provide various olefins possessing potential utility for synthesis, These methodologies have been utilized for the synthesis of polyoxygenated natural products and derivatives.

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Documento generato il 15/07/20 alle ore 05:12:23