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Titolo:
STEREOCONTROL IN DIELS-ALDER CYCLOADDITION TO UNSATURATED SUGARS - REACTIVITIES OF CIS-DIENOPHILES WITH CYCLOPENTADIENE
Autore:
HORTON D; KOH D; TAKAGI Y;
Indirizzi:
AMERICAN UNIV,DEPT CHEM,4400 MASSACHUSETTS AVE NW WASHINGTON DC 20016 OHIO STATE UNIV,DEPT CHEM COLUMBUS OH 43210
Titolo Testata:
Carbohydrate research
fascicolo: 2, volume: 250, anno: 1993,
pagine: 261 - 274
SICI:
0008-6215(1993)250:2<261:SIDCTU>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
NORBORNENE DERIVATIVES; ASYMMETRIC-SYNTHESIS; ACYCLIC SUGARS; DIENES; ACIDS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
29
Recensione:
Indirizzi per estratti:
Citazione:
D. Horton et al., "STEREOCONTROL IN DIELS-ALDER CYCLOADDITION TO UNSATURATED SUGARS - REACTIVITIES OF CIS-DIENOPHILES WITH CYCLOPENTADIENE", Carbohydrate research, 250(2), 1993, pp. 261-274

Abstract

Cycloaddition of cyclopentadiene with a D-arabinose-derived cis-dienophile, methyl etra-O-acetyl-2,3-dideoxy-D-arabino-hept-2-enonate (2), under thermal conditions gave essentially a single norbornene aduct, isolated crystalline in 81% yield and identified by NMR spectroscopy and X-ray crystallography as methyl -1-yl)bicyclo[2.2.1]-hept-2-ene-5-endo-carboxylate (3). The diene adds exclusively from the si-face of thedienophile and give only the endo product. The same sequence startingfrom L-arabinose gave the enantiomer (7) of 3. In contrast, a relatedcis-dienophile (9) having a butenolide ring reacts with cyclopentadiene from the opposite( re) face giving mainly the endo adduct i-O-acetyl)-D-arabino-tetritol-1-yl)bicyclo[2.2.1] hept-2-ene-5-endo-carboxylicacid 1,4-lactone (10), isolated crystalline in 70% yield, whose structure was again established by NMR spectroscopy, and firmly consolidated by X-ray crystallography. The minor (11%) product was the exo(5S,6R)isomer 11. A cis-enonate 14, analogous to 2 but deoxygenated at the allylic position, showed negligible diastereofacial selectivity and reacted with cyclopentadiene to give a mixture of all four possible adducts. A 6-membered ring dienophile 16 was also subjected to the same cycloaddition for comparison with the butenolide 9; it gave principally the two endo products 17 and 19 in 31 and 38% yields, respectively, accompanied by 12% of a mixture of the two exo products (18 and 20). The quantitative distribution of cycloaddition products as a function of dienophile stereochemistry is discussed. The high degree of asymmetric induction observed, especially with the readily accessible dienophiles2 and 7, provides a valuable route of access to enantiomerically puretetra-C-substituted cycloalkanes.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 07:50:52