A novel construction method for germacrene skeleton such as 3,7-dimethyl-10S^*-(1-methylethenyl)-2E,6E-cyclodecadien-1S^*-ol (18) by the stereoselective [2,3]-Wittig rearrangement of 3,6,10-trimethyl -1-oxa-2E,5E,9E-cyclotridecatriene (15) is presented. The stereoselectivity of this [2,3]-Wittig rearrangement is discussed based on the MM2 calculation. The stereoselective synthesis of(±) -4S^*-isopropyl-7R^*-(t-butyldiphenylsiloxy)methyl-9R^*,10R^*-epoxy-5-cyclodecen-1-one (43), as a precursor of Periplanone-B; the potent sex attractant and sex exitant pheromone of the American cockroach, is presented. In this synthesis,the 10-membered ring is constructed by the intramolecular alkylation of carbanion, generated from the protected cyanohydrin 41 and the stereoselective epoxydation of the enone 31 provides only the desired isomer 43. The stereoselectivity of the epoxydation is also discussed based on the MM2 calculation.