2-(3-Amino-5,6-dichloro-pyrazin-2-ylsulfanyl)-but-2-enedioic acid dimethyl ester AIDS-080213 AIDS080213 NSC371640 compound with (6,7-dichloro-3-oxo-3,4-dihydro-pyrazino[2,3-b][1,4]thiazin-2-ylidene)-acetic acid methyl ester (1:1)