Significant advances have been made by Proctor, Stolz, and others, demonstrating the value of this strategy. In order to further extend the generality of this strategy for broader applications, the development of complementary methods is urgently required. To this end, we sought to explore the ring expansion on the unfavorable ring strain fused-cyclic system using alkynes in the presence of a base to afford these synthetically challenging fused seven-membered bicyclic scaffolds (Scheme 1d). This unique method can serve as a straightforward and powerful platform for the synthesis of a variety of functionally fused seven-membered polycyclic systems. Based on this strategy, we realized the total synthesis of two sesquiterpenoid natural products plecarpenene and plecarpenone, and achieved the key core for the total synthesis of echinopines. All the synthesized structures bear a highly strained fused bicyclo[5.3.0]decane motif.