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

Abstract

The enantioselectives ynthesis of (À)-dihydroraputindole Di sr eported.T he key step is the desymmetrizing benzoylation of ap rochiral 1,3-diol employing Trost's ProPhenol catalyst system, which has been applied for the first time to ac yclic molecule carrying geminal hydroxymethyl groups. The cyclopenta[f]indoline system was assembled by Au(I)-catalyzed cyclization of an alkynylated indoline precursor.(À)-Dihydroraputindole Dw as obtained in 17 steps and 8% overall yield starting from dihydroxyacetone. In combinationw ith quantum chemical calculations of the ECD spectra, our synthesis allowed us to determine the absolutec onfiguration (5S,7R)o ft he natural product (+)-raputindole Df rom the Rutaceousp lant Raputia simulans. Scheme1.Structures of raputindoles A(1)and D(2)f rom the Peruvian rutaceous plant R. simulans,m odel of ap ossible ProPhenolcatalyst-substrate complex, and synthetic strategy.