Significance: The CCR3 antagonist M is a potential treatment for asthma and allergic rhinitis. The synthesis depicted provided 20 kg of the target. Key steps include the asymmetric hydrogenation of B to C and the quinidine-mediated desymmetrization of the meso-anhydride E.Comment: Note the 172 mol-scale Curtius rearrangement using diphenylphosphoryl azide by which H was converted into carbamate I.
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