Carbohydrate-Derived Chiral Furanosidic α,β-Unsaturated Aldehydes in Conjugate and Diels-Alder Addition Reactions. Steric Hindrance by the Anomeric Substituent
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 bulki
