Nadolol impurity G

Nadolol impurity G is a structurally related synthetic byproduct arising from the partial reduction of the parent drug's sulfonyl group during API synthesis. It retains the 1-(2-methoxyphenoxy)propan-2-ol backbone but features a desulfurized linkage at the beta-position, substituting the sulfonamide functionality with a secondary amine. This impurity exhibits a distinct UV absorption profile due to the absence of conjugated aromatic sulfonamide moieties. It serves as a critical HPLC reference standard for quantifying process-related impurities in nadolol formulations.