14-Step Synthesis of (+)-Ingenol from (+)-3-Carene
Ingenol is a diterpenoid with unique architecture and has derivatives possessing important anticancer activity, including the recently Food and Drug Administration–approved Picato, a first-in-class drug for the treatment of the precancerous skin condition actinic keratosis. Currently, that compound is sourced inefficiently from Euphorbia peplus. Here, we detail an efficient, highly stereocontrolled synthesis of (+)-ingenol proceeding in only 14 steps from inexpensive (+)-3-carene and using a two-phase design. This synthesis will allow for the creation of fully synthetic analogs of bioactive ingenanes to address pharmacological limitations and provides a strategic blueprint for chemical production. These results validate two-phase terpene total synthesis as not only an academic curiosity but also a viable alternative to isolation or bioengineering for the efficient preparation of polyoxygenated terpenoids at the limits of chemical complexity.
Benzylidene Acetal Fragmentation Route to 6-Deoxy Sugars: Direct Reductive Cleavage in the Presence of Ether Protecting Groups, Permitting the Efficient, Highly Stereocontrolled Synthesis of β-D-Rhamnosides from D-Mannosyl Glycosyl Donors. Total Synthesis of α-D-Gal-(1→3)-α-D-Rha-(1→3)-β-D-Rha- (1→4)-β-D-Glu-OMe, the Repeating Unit of the Antigenic Lipopolysaccharide from Escherichia hermannii ATCC 33650 and 33652.