Synthesis of [4-13C]-Isoflavonoid Phytoestrogens

Efficient syntheses are described for 13C-labelled derivatives of the isoflavonoid phytoestrogens, genistein, biochanin A, daidzein and formononetin, for use in metabolic studies. The synthetic procedure employs 13C-labelled cyanide as the source of the label to produce the isoflavones with a single 13C atom at the C-4 position.