Synthetic studies in the diterpene series. Part VIII. Synthesis of miltirone, a diterpenoid quinone

Miltirone (I), a diterpenoid quinone has been synthesised from p-bromoanisole, the key intermediate being 6-isopropyl-7-methoxy-1-tetralone (VI). A Reformatsky reaction on compound (VI) with methyl γ -bromocrotonate, followed by aromatisation, treatment with methylmagnesium iodide, and cyclisation gave 1,2,3,4-tetrahydro-1,1 -dimethyl-6-methoxy-7-isopropylphenanthrene. The corresponding phenol was oxidised to a quinone, identical with miltirone, either by air or by Fremy's salt