An Efficient Method for the Glycosylation of Isoflavones

The isoflavone phytoestrogens are still of current interest for their positive and negative health benefits. However, there are still many unanswered questions regarding their absorption, metabolism and bioavailability. Studies in this area require access to samples of both the isoflavone 7-O-glucosides, the form found in plants and the 7-O-glucuronides, which are important mammaliam metabolites. A new efficient, high-yielding glycosylation procedure is described for isoflavones, which employs 2,2,2-trifluoro-N-(p-methoxyph enyl)acetamidates as the glycosyl donors. This methodology was used to prepare the 7-O-glycosides of the three main isoflavones, daidzein, genistein and glycitein. The isoflavones were protected with hexanoyl groups which improved their solubility in organic solvents and improved the efficiency of the reaction, The same methodology was then adapted for the synthesis of the analogous 7-O-glucuronides. The new synthesis will provide access to large quantities of these compounds for further biological studies. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)