Synthesis of 1-Indolyl-3,5,8-Substituted γ-Carbolines: One Pot Metal-Solvent Free Protocol and Biological Evaluation

1,5 - Disubstituted indole-2-carboxaldehyde derivatives ( 1a – h ) and glycine alkyl esters ( 2a – c ) are shown to undergo a novel cascade imination-heterocylisation in the presence of organic base DIPEA to provide 1-indolyl 3,5,8-substituted g-carbolines ( 3aa – ea ) in good yields. The g-carbolines are fluorescent and exhibit anticancer activities against cervical, lung, breast, skin and kidney cancers.