Studies on the Diels–Alder reaction of annulated furans: application to the synthesis of substituted phenanthrenes

Electrochemically Enabled Total Syntheses of Natural Products

Electrochemical techniques have helped to enable the total synthesis of natural products since the pioneering work of Kolbe in the mid 1800's. The electrochemical toolset grows every day and these new possibilities change the way chemists look at and think about natural products. This review provides a perspective on total syntheses wherein electrochemical techniques enabled the carbon─carbon bond formations in the skeletal assembly of important natural products, discussion of mechanistic details, and representative examples of the bond formations enabled over the last several decades. These bond formations are often distinctly different from those possible with conventional chemistries and allow assemblies complementary to other techniques.

Synthesis of ent-Cleistanthane Diterpenoid Spruceanol: Construction of an Aromatic C Ring via Lewis Acid-Controlled Regioselective Diels-Alder Cycloaddition

The first synthesis of ent-cleistanthane-type diterpenoid spruceanol with significant anticancer activity is described. A chiral pool approach was employed with a linear sequence of 13 steps beginning from readily available and inexpensive andrographolide. The approach features the construction of an aromatic ring with hydroxyl and methyl groups at C-12 and C-13 of the target compound, respectively, via Lewis acid-controlled regioselective Diels-Alder cycloaddition and the regioselective removal of the primary hydroxyl group of the Diels-Alder adduct.