A photocatalytic
radical cascade with an unusual endo-trig cyclization
was developed, which enables the efficient assembly
of divergent tricyclic diterpenoid frameworks. The first total synthesis
of abietane 10-epi-epoxyhinoliol was thus achieved
in six steps by a subsequent reductive coupling of i-PrBr under photoredox/nickel dual catalysis. Inhibitory tests of
chiral 10-epi-epoxyhinoliol and its analogues in
4T1 cancer cells demonstrated the critical role of the C12 hydroxyl
group, leading to a discovery of the simplified analogue with better
activity.