A concise and efficient approach was established for the divergent totalsynthesis of (±)-tanshindiol B and C and tanshinone I from a ubiquitous ene intermediate in 1–2 steps. This critical intermediate was derived from (±)-tanshinol B, which was synthesized in 50% overall yield over 3 steps using an ultrasound-promoted cycloaddition as a key step. Compared to a previously reported strategy, our approach