POTENTIAL INTERMEDIATES FOR DITERPENOID QUINONES: CRYPTOTANSHINONE, TANSHINONE IIA, AND MILTIRONE

The transformation of the cyclic ethers (1) and (11) to dimethyl tetraol (8) and tetrahydrophenanthrene (14) respectively is described. These compounds proved to be a useful building block for the synthesis of angularly fused diterpenoid quinones.