New derivatives of 1,3,4-benzotriazepin-5-one were designed and synthesized as structural analogues to the antitumor agents devazepide and asperlicin. An efficient and novel approach to the synthesis of 2-amino-1,3,4-benzotriazepin-5-one 2 was developed and its structure was confirmed. The newly synthesized derivatives were evaluated for their in vitro antitumor activity on 60 different cell lines. Compounds 8 and 9 displayed the most potent antitumor activity against several cell lines specifically ovarian cancer, renal cancer and prostate cancer, while compounds 5, 10 and 12 showed significant activities against UO-31 renal cancer cell line.