23509-81-1 3,3'-Ethylenebis(4-hydroxy-4-methyl-2-thioxo-5-thiazolidinecarboxylic acid) diethyl ester 5-Thiazolidinecarboxylic acid, 3,3'-ethylenebis(4-hydroxy-4-methyl-2-thioxo-, diethyl ester