Dorzolamide Impurity 3

Chemical Name: (4S,6S)-4-(ethylamino)-N-(((4S,6S)-4-(ethylamino)-6-methyl-7,7-dioxido-5,6-dihydro-4H-thieno[2,3-b]thiopyran-2-yl)sulfonyl)-6-methyl-5,6-dihydro-4H-thieno[2,3-b]thiopyran-2-sulfonamide 7,7-dioxide, sodium salt