The synthesis of multiply 13C‐labelled plant and mammalian lignans as internal standards for LC‐MS and GC‐MS analysis

The syntheses of multiply 13C‐labelled derivatives of the two mammalian lignans, enterolactone and enterodiol, and two of their plant lignan precursors, secoisolariciresinol and matairesinol, are described. Three 13C atoms were incorporated into each lignan using potassium [13C]cyanide as the source for all of the 13C atoms. The compounds were prepared for use as internal standards in the LC‐MS and GC‐MS analysis of lignans.