1,3-Dithiole-4,5-dicarboxylic acid, 2,2'-[2,3-bis[4,5-bis(methoxycarbonyl)-1,3-dithiol-2-ylidene]-1,4-dibromo-1,4-butanediylidene]bis-, tetramethyl ester AIDS-136829 AIDS136829 NSC639816