Total Synthesis of Tanshinone I.

A novel total synthesis of tanshinone I (1) via the intermediate 3-hydroxy-8-methyl-1,4-phenanthrenedione (8) is described. The low overall yields and the use of expensive reagents in the synthesis process were minimized by the use of the Diels-Alder reaction to directly construct the 1,4-phenanthrenedione scaffold, providing tanshinone I (1) in only three steps.