Efficient Synthesis of Novel 1-Substituted β-Carboline Derivatives via Pictet-Spengler Cyclization of 5-Hydroxy-L-Tryptophan

A facile synthesis of novel 1-substituted beta-carboline derivatives by using three efficient reaction steps was described. The synthetic route began with the construction of beta-carboline frameworks involving the coupling of 5-hydroxy-L-tryptophan with different substituted phenylglyoxal via Pictet-Spengler condensation. Subsequent reduction of carbonyl functionality on carbon-7' by using Wolff-Kishner reaction followed by N-alkylation afforded a practical access to a series of 1-substituted beta-carboline derivatives in moderate yields. These novel derivatives were successfully synthesized without the use of expensive metal catalyst, prolonged reaction hours or critical reaction conditions. The molecular structures of all synthesized derivatives were confirmed by infrared (IR), gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy.