Abstract Cinchona alkaloids catalyze the oxa-Michael cyclization of 4-(2-hydroxyphenyl)-2- butenoates to benzo-2, 3-dihydrofuran-2-yl acetates and related substrates in up to 99% yield and 91% ee (ee= enantiomeric excess). Catalyst and substrate variation studies reveal an important role of the alkaloid hydroxy group in the reaction mechanism, but not in the sense of a hydrogen-bonding activation of the carbonyl group of the substrate as assumed ...
