Highly Diastereoselective and Asymmetric Diels−Alder Reactions of Masked <i>o</i>-Benzoquinones with Chiral Racemic and Homochiral Furans. Synthesis of Optically Active Tricyclic γ-Lactones
[reaction: see text] The first examples of highly diastereoselective and asymmetric Diels-Alder cycloadditions of in situ generated masked o-benzoquinones (MOBs) with chiral racemic and homochiral furans bearing a chiral center in the alpha-position leading to highly functionalized diastereomeric/enantioselective tricyclic heterocycles and chiral tricyclic gamma-lactones are described.