First Direct Isolation of Stable α-Form Crystals of Mirabegron, a Selective β3-Adrenoceptor Agonist.

An efficient and scalable method for the direct isolation of stable α-form crystals of Mirabegron (1) is developed. The developed method negates transformation of metastable β-form crystals into α-form crystals thereby overcoming the limitations of reported methods and avoids additional processing steps during its manufacture. The developed method directly provides stable α-form crystals of Mirabegron (1) with yield of around 84% and purity of >99.77% by HPLC in a single step.