1,4-Diphenylcyclopent-2-ene 1,4-endoperoxide on catalysis with trimethylsilyl trifluoromethane-sulfonate reacted with (−)-menthone in a doubly diastereoselective manner to yield two tricyclic 1,2,4-trioxanes having the 3S,5S,6S and 3R,5R,6R configurations respectively. The corresponding pair of 1,3-dioxolanes arising by Baeyer-Villiger-type rearrangement was also formed.