Protecting-Group-Free Synthesis of Taiwaniaquinone H Using a One-Pot Thermal Ring Expansion/4π-Electrocyclization Strategy

A strategy to the 6-5-6 tricyclic scaffold of taiwaniaquinoids was established on the basis of a one-pot thermal ring expansion/4π-electrocyclization process. The efficiency of this methodology has been demonstrated through its application in the total synthesis of taiwaniaquinone H, which has been accomplished in three steps and 14% overall yield in a protecting-group-free manner starting from commercially available materials

Total Synthesis and Structural Reassignment of (±)-Cereoanhydride

The first total synthesis of (±)-cereoanhydride has been achieved under the inspiration of its biosynthetic hypothesis. The tricyclic skeleton of trypethelone, the proposed biosynthetic precursor of cereoanhydride, was constructed by an interesting ring expansion of cyclobutenone in one step in which the introduced acetyl group is pivotal to avoid the following aerial oxidation. On the basis of X-ray crystallographic analysis, the structure of cereoanhydride is reassigned to a spiroketal structure <b>2</b>, which should be formed through an isomerization of the originally proposed structure <b>1</b>

Total Synthesis of Asterredione

The first total synthesis of asterredione was efficiently accomplished over five linear steps and in 21.5% overall yield. As the crucial step, the 2-quaternary 1,3-cyclopentenedione skeleton of asterredione was readily achieved using the Darzens/ring-expansion strategy developed in our laboratory. The structure of synthesized asterredione was fully confirmed by X-ray crystallography

Racemic synthesis of an intermediate for the formal synthesis of madindoline A and B

<p>On the basis of the application of the Darzens/ring-expansion process of cyclobutenedione developed previously by our group, a new strategy for the multisubstituted cyclopentene units of madindoline A and madindoline B has been reported in this paper. In light of the strategy, the synthesis of racemic Omura’s intermediate was finished in four steps and 34% overall yield, which furnished a new formal synthetic route to madindolines A and B.</p