Efficient TBD-Catalyzed Synthesis of Capsaicin-like Molecules

Capsaicin, the natural compound responsible for the spicy flavor in pepper fruits, has shown antioxidant and weight-reductive properties, cardiovascular benefits, anti-carcinogenic activity and recently pain relief effects. Studies on a series of synthetic capsacinoids indicated that the length of alkyl chain affected piquancy, with the possibility of obtaining non‐pungent capsaicin analogues of potential interest for clinical application perspectives. We report here on a new efficient procedure for the synthesis of capsaicin analogues, based on the aminolysis of vanillylamine with methyl esters showing structural changes in alkyl chain, catalyzed by the inexpensive and non-toxic triazabicyclo[4.4.0]dec‐5‐ene (TBD). It is a valid alternative to the known synthesis of this class of molecules, based on chemical reactions involving acyl chloride or lipase–catalyzed procedure. The TBD-method is improved by microwave irradiation, which allows to carry out the reaction under solvent-free conditions and to obtain high yields of products. This is an effective and eco-friendly approach for the access to a wide library of capsaicinoids for further biological evaluations, as well as for a large-scale production.