Vestipitant (1) is a novel NK1 antagonist currently under investigation for the treatment of CNS disorders and emesis. The first synthetic step comprised a Grignard synthesis. An impurity was identified and initially expected to be a symmetric biphenyl. This paper reports the work to synthesise the supposed structure and the spectroscopic analyses (LC-NMR and HR-NMR) to correctly identify the real structure and understand the chemical pathway of the impurity.
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