Dorzolamide EP Impurity B

: rac-cis Dorzolamide HCl; Dorzolamide Related Compound B USP; (4RS,6SR)-4-(Ethylamino)-6-methyl-5,6-dihydro-4H-thieno[2, 3-b]thiopyran-2-sulfonamide 7,7-dioxide HCl; cis-4-(Ethylamino)-5,6-dihydro-6- methyl-4H-thieno[2,3-b]thiopyran-2-sulfonamide 7,7-Dioxide Monohydrochloride; (4R,6S)-rel-4-(Ethylamino)-5,6-dihydro-6-methyl-4H-thieno[2,3-b]thiopyran-2-sulfonamide 7,7-Dioxide Monohydrochloride;