Asymmetric total syntheses of immunosuppressive diterpenoids triptobenzenes N and R via a remote Csp3–H functionalization

Abstract

The total syntheses of the naturally occurring diterpenoids triptobenzenes N (1c) and R (1d) have been accomplished via a late-stage δ-Csp³–H functionalization of an enone intermediate. The highly functionalized dienone intermediate 2 was utilized as a common scaffold for this study. An XRD analysis of compounds 8 and 4 confirmed the stereochemistry of the quaternary centers of the abietane core. Finally, a chemoselective ketal protection and reduction completed the first total syntheses of the immunosuppressive diterpenoids triptobenzenes N (1c) and R (1d).