Abstract The use of rigid spirocyclic dioxinones having 1-menthone as the chiral auxiliary as the enones in the photo [2+ 2] cycloaddition reactions opened novel methods for obtaining enantiomerically pure compounds, such as iridoids. Convex side preference of the sofa- conformation of these dioxinones in the photoaddition to cyclopentene increases up to 100% by introducing either a bulky substituent or 5-hexenyl group at the 3-position to ...
