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Synthesis of highly pure 14 C‐labelled DL ‐allantoin and 13 C NMR analysis of labelling integrity
Author(s) -
Patching Simon G.
Publication year - 2009
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.1614
Subject(s) - allantoin , yield (engineering) , chemistry , labelling , bicyclic molecule , methanol , proton nmr , stereochemistry , organic chemistry , materials science , biochemistry , metallurgy
A number of synthetic approaches are assessed to prepare allantoin labelled with 14 C given certain requirements and technical limitations. A method that fulfils these criteria is described to achieve the synthesis of highly pure 14 C‐labelled allantoin with the label introduced to the ureido carbonyl group in the final step by reaction of 5‐chlorohydantoin with [ 14 C]urea. The chosen method favours high purity at the expense of radiochemical yield, which is achieved at a level of 8%. The integrity of the label is then investigated by performing an NMR analysis of 13 C‐labelled allantoin synthesized by the same method. The 13 C NMR spectrum confirms partial scrambling of the label to the C‐2 position by equilibration of the product via a putative bicyclic intermediate, which had been suggested by other workers. The 14 C‐labelled allantoin synthesized by this method is therefore assigned as DL ‐[H 2 N 14 CO/ 14 C‐2]allantoin. This study also includes the first full characterization of a side product, 5‐hydroxy‐5‐methoxyhydantoin, obtained by the reaction of a 5‐hydroxyhydantoin intermediate with the methanol solvent. Copyright © 2009 John Wiley & Sons, Ltd.