Timolol impurity G

Timolol impurity G is a thiazole-containing synthetic byproduct arising from the amidation step in Timolol manufacturing. It features a 1,3-thiazole ring fused to a substituted pyrrolidin-2-one moiety, with a terminal amino group and a hydroxylated side chain. The compound lacks the methoxy substitution present in the parent drug, instead bearing a free amine and an additional hydroxyl group at the β-position. This structural divergence confers distinct chromatographic properties, enabling its identification as a critical process-related impurity. It serves as an HPLC reference standard for quantifying residual synthetic intermediates in Timolol API batches.