Figure 1: Three-dimensionally cage-like diterpenes and diterpenoid alkaloids.

(a) Selected members of three related types of diterpenes and their alkaloidal congeners. Among them, the arcutane diterpenes (that is, 3) and arcutine alkaloids (that is, 6), containing a unique tetracyclo[5.3.3.04,9.04,12]tridecane moiety (shown in blue bonds) and two all-carbon bridgehead quaternary centres (C5 and C8), posed formidable synthetic challenges. (b) Recent accomplishments in the total synthesis of complex atisane-type diterpenes and diterpenoid alkaloids. Ac, acetyl; i-Pr, isopropyl.