5-Bromo-4-chloro-3-indolyl 2-​Azido-​2-​deoxy-​3,​4,​6-​triacetate-α-D-galactopyranoside is an impurity in the synthesis of 5-Bromo-4-chloro-3-indolyl 2-Acetamido-2-deoxy-α-D-galactopyranoside (B682250), which is a histochemical substrate for a-N-acetyl-galactosaminidase.