Microwave-assisted traceless synthesis of hydantion-fused β-carboline scaffold

Multistep microwave-assisted reactions toward the synthesis of hydantoin-fused tricyclic tetrahydro-β-carbolines on the soluble polymer support have been developed. Polymer-bound tryptophan with various aldehydes has been subjected to Pictet–Spengler reaction to obtain tricyclic β-carboline conjugates. The terminal hydantoinyl moiety is constructed across polymer-bound β-carbolines by the reaction with various isocyanates under microwave irradiation to form urea intermediate. Simultaneous intramolecular cyclization of urea followed by cleavage of the polymer support leads to a traceless synthesis of tetracyclic scaffolds in high yield and high purity.