Many diseases are dependant of the concentration of hormones in our body, especially for women. The risk of having this type of disease such as sex-related cancer is lower in Asian countries thanks to the high consumption of soy in these countries. Indeed, soy contains several isoflavones such as daidzein or genistein which act as phytoestrogens once metabolized in our body. It is due to the fact that they are similar to estrogens but they do not have or have a lower biological effect than estrogens compounds. (S)-dihydrodaidzein, a product of the metabolism of daidzein which is one of these isoflavones, has a stronger bioactivity than its parent compound but only 30% of the population in the world can obtain it naturally.
The current research was focused on the stereoselective synthesis of dihydrodaidzein by hydrogenation using a chiral catalyst that will favor the obtention of only one enantiomer. (S)-proline was used as the chiral modifier. Two types of hydrogenation were used, transfer hydrogenation and hydrogenation under pressure, the latter being the one where we obtained the maximum of enantiomeric excess. 44% was achieved after 3 hours of hydrogenation with palladium on activated carbon as catalyst at 20 bars of pressure of dihydrogen. It is the first report of the use of (S)-proline on another compound than isophorone and we obtained higher enantiomeric excess for the same conditions.
This study relies on the use of one and two-dimensional NMR, preparative HPLC-MS and chiral HPLC to identify and to obtain pure compounds and the enantiomeric excess of dihydrodaizein. Future research should focus on the kinetic study of this reaction and the elucidation of the mechanism.
