Fluorous and traceless synthesis of substituted indole alkaloids.

The fluorous traceless synthesis of substituted indole alkaloids is carried out first by attaching the 3-(perfluorooctyl)propanol with Boc protected L-tryptophan. The reaction of perfluoroalkyl (Rfh)-tagged tryptophan esters with various aldehydes undergoes Pictet-Spengler reaction to give cis and trans stereoisomers of tetrahydro-beta-carbolines. The nucleophilic addition of the piperidine nitrogen across various isocyanates is followed by the cyclization of ureas and simultaneous rupture of the fluorous tag to afford the hydantoin ring fused tetrahydro-beta-carbolines. All the fluorous-tag compounds are purified by solid-phase extraction (SPE) through Fluoro Flash cartridges.