Chiral- Amine- Catalyzed Asymmetric Bromocyclization of Tryptamine Derivatives

Chiral hexahydropyrro[2,3]indole (HPI) units exist widely in natural and unnatural products with significant biological activities. The enantioselective synthesis of brominated hexahydropyrrolo[2,3-b]indole (HPI) subunits by asymmetric bromocyclization of tryptamine derivatives catalyzed by a chiral amine has been realized. In the presence of hydroquinine 1,4-phthalazinediyl diether ((DHQ)(2)PHAL, 20mol%) and L-(-)-camphorsulfonic acid (20mol%), enantioenriched brominated HPI derivatives were obtained from readily available substituted tryptamines in up to 99% yield and 73%ee.