Synthesis of (−)‐Dihydroraputindole D by Enantioselective Benzoylation of a 1,3‐Diol Intermediate

The enantioselective synthesis of (−)‐dihydroraputindole D is reported. The key step is the desymmetrizing benzoylation of a prochiral 1,3‐diol employing Trost′s ProPhenol catalyst system, which has been applied for the first time to a cyclic molecule carrying geminal hydroxymethyl groups. The cyclopenta[f]indoline system was assembled by Au(I)‐catalyzed cyclization of an alkynylated indoline precursor. (−)‐Dihydroraputindole D was obtained in 17 steps and 8% overall yield starting from dihydroxyacetone. In combination with quantum chemical calculations of the ECD spectra, our synthesis allowed us to determine the absolute configuration (5S,7R) of the natural product (+)‐raputindole D from the Rutaceous plant Raputia simulans.