DISEASE CHARACTERISTICS:

• Diagnosis of one of the following:

  • Relapsed or refractory acute leukemia (acute myeloid leukemia [AML], acute lymphoblastic leukemia [ALL], or acute leukemia unclassifiable) following at least one prior systemic treatment
  • Acute leukemia in a patient 60 years or older (no requirement for prior treatment)
  • Acute leukemia that has evolved from a prior myelodysplastic syndrome
  • Chronic myelogenous leukemia (CML) in blast crisis following prior imatinib mesylate therapy
  • Refractory anemia with excess blasts-2 (RAEB-2)
• No known CNS leukemia

PATIENT CHARACTERISTICS:

• ECOG performance status 0-2

• WBC < 50,000µL

  • Hydroxyurea and/or leukaphereses may be used to lower WBC
• Creatinine ≤ 1.5 times upper limit of normal (ULN) OR creatinine clearance ≥ 50 mL/min
• Total bilirubin ≤ 2 times ULN
• AST/ALT ≤ 2.5 times ULN
• QTc interval ≤ 0.470 seconds
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 3 months after study participation
• No other condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

• At least 3 weeks since prior treatment (expect leukaphereses)
• No valproic acid therapy within the past 2 weeks
• No prior autologous or allogeneic bone marrow or stem cell transplantation
• No hydroxyurea use within the past 24 hours
• No concurrent treatment with other anti-cancer agents or investigational agents