Total synthesis of asymmetric flavonoids: the development and applications of 13C-labelling

This article compiles our results in the field of flavonoid chemistry with the aim to synthesise isotopically labelled products. Two strategies (C₆ + C₃–C₆ vs C₆–C₂ + C₁–C₆) and some organometallic (Pd⁰, Mo^IV) couplings were explored to build the C₆–C₃–C₆ flavonoid skeleton. Following this work, the gram scale has been reached in addition to the asymmetry of the targeted natural flavan-3-ols, i.e. (+)-catechin, (–)-epicatechin, and (–)-procyanidin B3. These characteristics were necessary in the event of using these molecules for pharmacokinetic and metabolic studies in human beings.