The cancer is among the most important diseases of our time, being the second leading cause of death in developed countries. The development of more effective chemotherapeutic drugs is one of the challenges of medicinal chemistry. Considering the cytotoxicity of quinones, the lapachol 1 and the β-lapachone 2 are attractive molecules for the development of analogues with antitumor activity. Then, the lapachol 1 was used in the synthesis of the 1,4-naphthalenodione,2-hydroxy-3-(3-methyl-2-butenyl),1-oxime 3, the 1,4-naphthalenodione,2-(acetyloxy)-3-(3-methyl-2-butenyl)-1- (O-acetyloxime) 4 and the 2H-naphtho[1,2-b]pyran-5,6-dione, 3,4-dihydro-2,2-dimethyl-6-oxime 5 with yields of 60%, 90% and 62%, respectively. The MTT reduction method was used for determine the cytotoxicity of the molecules 3, 4 and 5 against cancer cells lines: HCT-116 (colon); SF-295 (central nervous system); NCI-1975 (lung) and HL-60 (leukemia). The compound 4 showed no cytotoxic activity against these tumor cells, with IC50> 10 μg/ml. The lapachol oxime 3 and the β-lapachone oxime 5 showed significant antitumor activity, in particular against HL-60 cells with IC50 of 10.20 and 3.84 μM, respectively. It is known that one of mechanisms of cytotoxicity demonstrated in quinones is by formation of reactive oxygen species, where the intermediate is the semiquinone radical. The most cytotoxic derivative, the β-lapachone oxime 5 may not generate semiquinone radical. Thus, this paper displays a new probable moiety with relevant antitumor activity, the nucleus 1,2-naphthoquinone-1-oxime.