Carbohydrate-Derived Chiral Furanosidic α,β-Unsaturated Aldehydes in Conjugate and Diels-Alder Addition Reactions. Steric Hindrance by the Anomeric Substituent
(1990) In Journal of Organic Chemistry 55(20). p.5477-5483- Abstract
The title aldehydes (lr, 1s, 2, and 3) underwent virtually diastereospecific conjugate addition by lithium methylcyanocuprate. The bulkiness of the anomeric benzyloxy or methoxy groups direct the attacking nucleophile to the less hindered side of the furanosidic ring. The stereochemical outcome of the Diels-Alder additions of cyclopentadiene to lr and 1s was governed almost completely by the bulkiness of the anomeric benzyloxy group, which directed cyclopentadiene to the less hindered side of the furanosidic ring. When an additional substituent was positioned trans to the anomeric substituent (2), a mixture of all four possible diastereomers was obtained. With both substituents on the same side of the ring (3), complete π-facial... (More)
The title aldehydes (lr, 1s, 2, and 3) underwent virtually diastereospecific conjugate addition by lithium methylcyanocuprate. The bulkiness of the anomeric benzyloxy or methoxy groups direct the attacking nucleophile to the less hindered side of the furanosidic ring. The stereochemical outcome of the Diels-Alder additions of cyclopentadiene to lr and 1s was governed almost completely by the bulkiness of the anomeric benzyloxy group, which directed cyclopentadiene to the less hindered side of the furanosidic ring. When an additional substituent was positioned trans to the anomeric substituent (2), a mixture of all four possible diastereomers was obtained. With both substituents on the same side of the ring (3), complete π-facial selectivity was obtained. In both the conjugate and Diels-Alder addition products, NMR data could be used to determine the stereostructures of all diastereomers. Both product types showed oxygen atom induced proton deshielding and carbon shielding effects in NMR.
(Less)
- author
- Rehnberg, Nicola LU ; Sundin, Anders LU and Magnusson, Göran LU
- organization
- publishing date
- 1990-09
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Organic Chemistry
- volume
- 55
- issue
- 20
- pages
- 7 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:0042251310
- ISSN
- 0022-3263
- DOI
- 10.1021/jo00307a018
- language
- English
- LU publication?
- yes
- id
- e0f17d30-0588-482b-863a-f161d43689d5
- date added to LUP
- 2021-11-11 12:01:06
- date last changed
- 2021-11-16 02:28:16
@article{e0f17d30-0588-482b-863a-f161d43689d5, abstract = {{<p>The title aldehydes (lr, 1s, 2, and 3) underwent virtually diastereospecific conjugate addition by lithium methylcyanocuprate. The bulkiness of the anomeric benzyloxy or methoxy groups direct the attacking nucleophile to the less hindered side of the furanosidic ring. The stereochemical outcome of the Diels-Alder additions of cyclopentadiene to lr and 1s was governed almost completely by the bulkiness of the anomeric benzyloxy group, which directed cyclopentadiene to the less hindered side of the furanosidic ring. When an additional substituent was positioned trans to the anomeric substituent (2), a mixture of all four possible diastereomers was obtained. With both substituents on the same side of the ring (3), complete π-facial selectivity was obtained. In both the conjugate and Diels-Alder addition products, NMR data could be used to determine the stereostructures of all diastereomers. Both product types showed oxygen atom induced proton deshielding and carbon shielding effects in NMR.</p>}}, author = {{Rehnberg, Nicola and Sundin, Anders and Magnusson, Göran}}, issn = {{0022-3263}}, language = {{eng}}, number = {{20}}, pages = {{5477--5483}}, publisher = {{The American Chemical Society (ACS)}}, series = {{Journal of Organic Chemistry}}, title = {{Carbohydrate-Derived Chiral Furanosidic <i>α</i>,<i>β</i>-Unsaturated Aldehydes in Conjugate and Diels-Alder Addition Reactions. Steric Hindrance by the Anomeric Substituent}}, url = {{http://dx.doi.org/10.1021/jo00307a018}}, doi = {{10.1021/jo00307a018}}, volume = {{55}}, year = {{1990}}, }