Abstract Robust and straightforward methods are described for the first syntheses of highly pure 13 C-and 14 C-labelled L-5-benzylhydantoin (L-BH) and L-5-indolylmethylhydantoin (L- IMH) by cyclizing the amino acids L-phenylalanine and L-tryptophan, respectively, with potassium cyanate.[3-13 C]-L-phenylalanine was used to prepare [6-13 C]-L-BH and [indole- 2-13 C]-L-tryptophan was used to prepare [indole-2-13 C]-L-IMH, which we required for ...
