Synthesis of the C/D/E-ring core compound of maoecrystal V

Maoecrystal V is a highly oxidized and rearranged norterpenoid isolated from the Chinese herb, Isodon eriocalyx. A synthetic route for the C/D/E-ring core compound of maoecrystal V has been developed. Introduction of the C1 fragment to the D/E-ring compound was achieved by lithito dithiane attack, and the C-ring was formed by deprotective intramolecular hemiacetalization of the dithiane-alcohol precursor. [GRAPHICS] .