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Iodine‐123 labeled derivatives of methylphenidate: Potential SPECT radiopharmaceuticals for brain dopamine transporters
Author(s) -
Pan D.,
Gatley S. J.,
Chen R.,
Ding Y.S.
Publication year - 1996
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/(sici)1099-1344(199606)38:6<523::aid-jlcr863>3.0.co;2-#
Subject(s) - chemistry , dopamine transporter , methylphenidate , dopamine , iodine 123 , pharmacology , transporter , neuroscience , biochemistry , medicine , attention deficit hyperactivity disorder , psychology , psychiatry , gene
Since dl‐threo ‐[ 11 C]methylphenidate (Ritalin) and especially the more active enantiomer, d‐threo ‐[ 11 C]methylphenidate, have favorable properties for PET studies, we prepared two radioiodinated analogs of methylphenidate, p‐[ 123 I]iodomethylphenidate and m‐[ 123 I]iodo‐p‐hydroxymethylphenidate with a view to evaluating them as potential SPECT tracers. To prepare p‐[ 123 I]iodomethylphenidate, the p‐tributyltin derivative was prepared from the previously reported p‐bromomethylphenidate and reacted under acidic conditions with I‐123 iodide plus chloramine‐T at room temperature for 90 seconds. The predominant radioactive product was obtained in 85% radiochemical yield and >10 Ci/μmol specific radioactivity after HPLC purification. It had the same HPLC retention time as a spectroscopically characterized non‐radioactive p‐iodomethylphenidate standard prepared via nitration of methylphenidate and diazotization, after protection of the secondary amino group by benzoylation. A second radioiodinated methylphenidate derivative, m‐[ 123 I]iodo‐p‐hydroxymethylphenidate was prepared in 80% radiochemical yield by direct iodination of the known p‐hydroxymethylphenidate. In this case the non‐radioactive standard was prepared by iodination of p‐hydroxyritalinic acid using I 2 and iodic acid, followed by esterification.