The first total synthesis of similisines A and B, a pair of unprecedented polybrominated spiro-trisindole enantiomers isolated from Laurencia similis, and their all stereoisomers had been accomplished in 6 steps from the known 5,6-dibromoindole. The described synthesis avoided any protecting-group manipulations, and the key all-carbon spirocenters were constructed via an intramolecular Friedel-Crafts cyclization. In addition, the rotamers of similisines and cytotoxic and NO production inhibitory activities of synthetic compounds were also discussed.