Atenlol Imp B

Atenlol Imp B is a synthetic byproduct arising from oxidative modification of the 4-hydroxyphenyl moiety in atenolol, featuring a carboxylic acid substitution at the C-4 position of the benzene ring. This structural alteration introduces a polar, zwitterionic character due to the adjacent amine and carboxylate groups, enhancing hydrophilicity compared to the parent compound. It serves as an HPLC reference standard for quantifying process-related impurities in atenolol drug substance.