摘要：

Halichlorine and Pinnaic acid are two novel marine natural products isolated from a Japanese sponge, and an Okinawan bivalve respectively. The unique azaspirl[4.5]decane-core structure prexent in both compounds provides a synthetic challenge, Herein, we describe a synthetic approach to the azaspiro[4.5]decane-core structure through an intramolecular[3+2] cycloaddition followed by an intra-molecular Michael addition and in situ isomerization to afford the azaspirocyclic core structures stereospecifically in 10 steps with 40% overall yield. Alternatively, the same core structure was achieved by tandem cycloaddition and isomerization approach.

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