Mirabimide E, a solid tumor selective cytotoxin from the terrestrial blue-green alga Scytonema mirabile UH strain BY-8-1, possesses an unprecedented tetrachlorinated ethylene group and has been identified as (5S,2’R,3’R)-N- (anti-8/,8’,9’,9’-tetrachloro-3’-(carbamoyloxy)-2’-methyldecanoyl)-4-methoxy-5-methyl-3-pyrrolin-2-one. The total structure, including absolute stereochemistry, of this novel N-acylpyrrolinone was concluded from a combination of spectral and chemical studies, including stereoselective syntheses of three degradation products, viz. methyl (2R,3R)-anti-8,8,9,9-tetrachloro-3-hydroxy-2-methyldecanoate, (5R,6R)-trans-5-methyl-6-(5,5’,6,6’-tetrachloroheptyl-1-oxa- 3-azacyclohexane-2,4-dione, and (5S)-4-methoxy-5-methyl-3-pyrrolin-2-one and the total synthesis of mirabimide E itself. The influence of the carbamate ester group on the chemical degradation and synthesis of mirabimide E is described.