Convenient synthesis of 1-aryl-9H-β-carboline-3-carbaldehydes and their transformation into dihydropyrimidinone derivatives by Biginelli reaction

In the present work, a practical synthesis of 1-aryl-β-carboline-3-carbaldehydes as versatile building blocks and their application in Biginelli reaction is reported. The starting material of the four-step synthesis is racemic tryptophan methyl ester. The procedure involves a Pictet-Spengler cyclization, a dehydrogenation, an ester reduction, and an alcohol oxidation step. The β-carboline-3-carbaldehydes were further transformed using a Biginelli reaction into derivatives containing a pharmacologically significant dihydropyrimidine ring at position-3.