Synthetic Studies on Flavan-Derived Natural Polyphenols: a Complex Molecular Platform in Organic Synthesis

Flavan-derived polyphenols are widely distributed in the plant kingdom, and have long been known to possess remarkable biological activity and a positive effect on human health. However, the detailed biochemical functions of this class of molecules at a molecular level are still not well studied due to the limited availability of natural samples in sufficient quantity and quality. This account gives an overview of our synthetic efforts towards this class of molecules which exploit selective functionalization of the C(4) position of the flavan skeleton. Various nucleophilic components could be introduced into this position via S(N)1-type substitution. As part of our synthetic studies on flavan oligomers, an orthogonal activation method that employs two distinct flavan units was developed. This enabled iterative coupling to give linear and/or doubly-linked flavan oligomers to be achieved.