Preparation of deuterium labelled catecholamines, catecholamine precursors and metabolites for use as internal standards in mass fragmentographic determination and for turnover studies

L‐dihydroxyphenylalanine‐ 2 H 3 , L‐tyrosine‐ 2 H 2 , dopamine‐ 2 H 3 , 3‐methoxytyramine‐ 2 H 3 , homovanillic acid‐ 2 H 2 , homovanillic acid‐ 2 H 5 and vanillylmandelic acid 2 H 2 were prepared by hydrogen‐deuterium exchange under acidic or basic conditions. 4‐hydroxy‐3‐methoxy phenylethyleneglycol‐ 2 H 3 was prepared from vanillylmandelic acid‐ 2 H by reduction with LiA1 2 H 4 . The isotopic yield for L‐dihydroxyphenylalanine was 90% and for the other compounds >99%. These labelled compounds could be used as internal standards in the mass fragmentographic analysis of the protium species in tissues and body fluids as well as in metabolic studies in vivo .