The present invention relates to a cyclization process of forming a multiple ring compound from an isoprenoid compound. The cyclization process involves reacting the isoprenoid compound with an acetal initiator under conditions sufficient to form the multiple ring compound. The isoprenoid compound is contacted with an initiator an optionally with a catalyst. Cyclization occurs by reaction of the initiator with the isoprenoid compound. Cyclic acetal compounds wherein the acetal forms part of 6-membered unsaturated ring are also defined.