Total Synthesis of <i>ent</i>-Ascospiroketal B

Ascospiroketal B was isolated from a marine-derived fungus as a structurally unique polyketide possessing a rare tricyclic core including 5,5-spiroketal-γ-lactone. An asymmetric total synthesis of <i>ent</i>-ascospiroketal B was achieved using an original synthetic route. The synthesis included the stereoselective construction of 5,5-spiroketal for ascospiroketal B and stereocontrolled construction of a quaternary asymmetric carbon by rearrangement of a trisubstituted epoxide

Amitorines A and B, Nitrogenous Diterpene Metabolites of <i>Theonella swinhoei</i>: Isolation, Structure Elucidation, and Asymmetric Synthesis

Two new nitrogenous prenylbisabolanes never before found in Lithistid sponges have been isolated from <i>Theonella swinhoei</i>. These new diterpenes, named amitorine A (<b>1</b>) and amitorine B (<b>2</b>), containing a prenylbisabolane skeleton have been characterized by spectroscopic analyses, and the relative and absolute configurations of <b>1</b> and <b>2</b> were determined by asymmetric synthesis of both diastereomers via the common bicyclic lactone <b>6</b> intermediate

Phellilane L, Sesquiterpene Metabolite of <i>Phellinus linteus</i>: Isolation, Structure Elucidation, and Asymmetric Total Synthesis

A new cyclopropane-containing sesquiterpenoid, phellilane L (<b>1</b>), was isolated from the medicinal mushroom <i>Phellinus linteus</i> (“Meshimakobu” in Japanese), a member of the Hymenochaetaceae family and a well-known fungus that is widely used in East Asia. The planar structure of <b>1</b> was determined on the basis of spectroscopic analysis. The authors achieved the first total synthesis of <b>1</b>. Our protecting group-free synthesis features a highly stereoselective one-pot synthesis involving an intermolecular alkylation/cyclization/lactonization strategy for construction of the key cyclopropane-γ-lactone intermediate. Additionally, our synthesis determined the absolute configuration of phellilane L (<b>1</b>)