Abstract
During the course of our study on the Diels-Alder (DA) reaction of 2-prone, we found that base catalyst was quite effective for the reaction of 3-hydroxy-2-pyrone with electron deficient dienophile. In particular, the reactions with the reactive dienophiles such as maleimides and acrylate derivatives proceeded quite rapidly in the presence of catalytic amount of triethylamine and the yields of the adducts were almost quantitative.
Enantio- and diastereoselective DA reactions of 3-hydroxy-2-pyrone were also achieved by using chiral base and chiral dienophile, respectively. The reaction with N-methylmaleimide catalyzed by cinchonidine afforded optically active adduct in 87% ee, and the reaction with chiral N-acryloyl oxazolidinone derivative gave the adduct in 95% de.
By using these reactions, pseudo-sugars and a key intermediate of substance P antagonist were synthesized.
