- Synthesis of the 3H-labelled 5-HT3 antagonist (RS-25259-197) at high specific activity
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The preparation of the title compound, a selective 5-HT3 antagonist with anti-emetic properties, is described. The key intermediate involved is 6-bromo-1,2-dihydronaphthoid acid (5), which was synthesized from 4-bromophenylacetic acid by Micheal addition, acid-induced ring cyclization, reduction and dehydration. Compound (5) was selected because it has two labelling sites to ensure high specific activity of the final product. Reduction of amide 6 with carrier-free tritium gas, followed by reduction of the amide functional group with BF3-OEt2 and intramolecular cyclization furnished the title compound having a specific activity of 70.4 Ci/mmol and >99% purity.
- Gong, Leyi,Pames, Howard
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