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A combined loop‐SPE method for the automated preparation of [ 11 C]doxepin
Author(s) -
Iwata R.,
Pascali C.,
Bogni A.,
Yanai K.,
Kato M.,
Ido T.,
Ishiwata K.
Publication year - 2002
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/jlcr.557
Subject(s) - doxepin , chemistry , chromatography , yield (engineering) , trifluoromethanesulfonate , extraction (chemistry) , solid phase extraction , high performance liquid chromatography , organic chemistry , catalysis , pharmacology , medicine , materials science , metallurgy
A simple and versatile loop‐solid phase extraction (SPE) method was developed for the automated preparation of [ 11 C]doxepin, a histamine H 1 receptor antagonist, from [ 11 C]methyl triflate ([ 11 C]MeOTf). This labeling agent was passed through a Teflon or Tefzel loop coated internally with a film of the precursor solution. The reaction products were then flushed from the loop to a short SPE column, where they were concentrated and then injected onto a semi‐preparative HPLC column simply by switching an injection valve. By applying this combined loop‐SPE technique the whole procedure turned out to be easily automated. The formation of [ 11 C]methylated doxepin ([ 11 C]methyldoxepin) was observed and the ratio of doxepin to methyldoxepin was found to be clearly correlated with the mass ratio of nordoxepin to MeOTf. This observation highlights the importance of [ 11 C]MeOTf specific activity in the [ 11 C]methylation of secondary amines. Using this method, [ 11 C]Doxepin was prepared in over 40% radiochemical yield from high specific activity [ 11 C]MeOTf. Copyright © 2002 John Wiley & Sons, Ltd.