Curran DP.
*
Rakiewicz DM.
University of Pittsburgh, USA
Tandem Radical Approach to Linear Condensed Cyclopentanoids. Total Synthesis of (±)-Hirsutene.
J. Am. Chem. Soc. 1985;
107: 1448-1449
Curran DP.
*
Rakiewicz DM.
University of Pittsburgh, USA
Radical-Initiated Polyolefinic Cyclizations in Linear Triquinane Synthesis. Model
Studies and Total Synthesis of (±)-Hirsutene.
Tetrahedron 1985;
41: 3943-3958
Key words
(±)-hirsutene - triquinanes - Ireland–Claisen rearrangement - radical cyclization
Significance
Hirsutene is a linear triquinane that was isolated from the fungi Coriolus consors in 1976. Its lack of heteroatomic functional groups along with the presence of four
contiguous stereocenters and two quaternary carbon atoms render this condensed cyclopentanoid
natural product challenging. In 1985, Curran and Rakiewicz reported an elegant synthesis
of (±)-hirsutene employing a late-stage radical cyclization.
Comment
Accessed in two steps from the corresponding enone, acetate A was converted into lactone B by Ireland–Claisen rearrangement followed by phenylselenolactonization. Elimination,
SN2′ reaction, and deprotection furnished carboxylic acid E. Further transformation led to iodoenyne H, which underwent 5-exo-trig/5-exo-dig radical cyclization cascade in the presence of AIBN/Bu3SnH to afford (±)-hirsutene.
