Chiral Phosphoric Acid-Catalyzed Pictet-Spengler Reactions for Synthesis of 5',11'-Dihydrospiro[indoline-3,6'-indolo[3,2-c]qui-nolin]-2-ones Containing Quaternary Stereocenters.

Chiral phosphoric acid-catalyzed Pictet-Spengler reactions of 2-(1H-indolyl)aniline derivatives and isatins by the condensation/cyclization process have been realized. A series of enantioenriched 5',11'-dihydrospiro[indoline-3,6'-indolo[3,2-c]quinolin]-2-ones bearing quaternary stereogenic centers were obtained with excellent yields and up to >99% ee. This protocol was suitable for the Pictet-Spengler reactions of 2-(1-benzyl-5-methyl-1H-pyrrol-2-yl)aniline, and a variety of 1',5'-dihydro-spiro[indoline-3,4'-pyrrolo[3,2-c]quinolin]-2-ones could also be obtained in good yields and up to 88% ee.