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The bowl-shaped tricyclo[6.3.1.04,12]dodecane moiety is the core feature of cephalotane-type diterpenoids. As part of our efforts directed towards a total synthesis of mannolide B, the bowl-shaped tricyclo[6.3.1.04,12]dodecane skeleton, a common intermediate of cephalotane-type diterpenoids bearing up to five contiguous stereocenters including two quaternary carbon centers had been constructed. The synthetic strategy was enabled by an efficient application of oxidative dearomatization/intramolecular Diels-Alder reaction to access highly functionalized building block with the tricyclo[5.2.2.02,6]undecane unit from commercially available materials. The key feature was firstly used the cyclic olefins with secondary alcohol as dienophile for the intramolecular inverse electron demand Diels-Alder reaction. Further synthetic studies led to construct ring D by a regioselective Aldol reaction.

A concise total synthesis of tetranorsesquiterpenoids applanatumol Z5 (3), possessing unique 6/5/5 ring system was disclosed with 7-step in 5-pot from commercially available starting materials. The key elements of the synthesis included an unexpected intramolecular dithiolane with alcohol oxidative coupling/deprotection sequence to create the unsaturated lactone as dienophile and a regioselective Diels-Alder reaction to assemble the 6/5/5 tricyclic scaffold including two vicinal quaternary carbon stereocenters. Late stage the diastereo- and regioselective carbonyl reduction led to achieve the total synthesis of (±) applanatumol Z5 (3).