.beta.,.beta.'-Dicarbomethoxydiethyl sulfide 4131-74-2 Bis(2-methoxycarbonylethyl)sulfide Dimethyl 3,3'-thiodipropionate Dimethyl thiodipropionate NSC2244 Propanoic acid, 3,3'-thiobis-, dimethyl ester Propionic acid, 3,3'-thiodi-, dimethyl ester