DIRECT NCA ELECTROPHILIC RADIOIODINATION OF TYROSINE ANALOGS - THEIR IN-VIVO STABILITY AND BRAIN-UPTAKE IN MICE

In order to improve tracers for amino acid transport studies with SPET we have radioionated methylated tyrosines and compared their brain up take and in vivo deiodination in mice. O-methylation not only leads to a higher lipophilicity and hence significantly higher brain uptake wi th a maximum of 5% dose/g for 3-[I-123]iodo-O-methyl-L-alpha-methyltyr osine (OMIMT) but also significantly prevents in vivo deiodination. Hi gh n.c.a. radioiodination yields (greater than or equal to 80%) are ob tained for the activated aromatic compounds L-tyrosine and L-alpha-met hyltyrosine using Iodo-gen(tm) in a heterogeneous aqueous system. Dire ct n.c.a. radioiodination of the less-activated O-methyl analogues has been achieved in reasonable yields (60%) with Iodo-gen(tm) in homogen eous TFA solutions containing about 10% of water.