Efficient syntheses of 13C- and 14C-labelled 5-benzyl and 5-indolylmethyl L-hydantoins

Robust and straightforward methods are described for the first syntheses of highly pure 13C- and 14C-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. [3-13C]-L-phenylalanine was used to prepare [6-13C]-L-BH and [indole-2-13C]-L-tryptophan was used to prepare [indole-2-13C]-L-IMH, which we required for solid-state NMR experiments with a hydantoin transport protein. The successful incorporation and integrity of the 13C labels was confirmed by solution-state NMR spectroscopy. [14C]Potassium cyanate was used to prepare [2-14C]-L-BH and [2-14C]-L-IMH, which we required for transport assays with the protein. Copyright © 2010 John Wiley & Sons, Ltd.