Azacitidine Plus Phenylbutyrate in Treating Patients With Acute Myeloid Leukemia or Myelodysplastic Syndrome

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed myelodysplastic syndrome (MDS) indicating one of the following: * Refractory anemia (RA) * Primary refractory leukopenia or thrombocytopenia with MDS morphology * RA with excess blasts (RAEB) * RA with ringed sideroblasts (RARS) * Chronic myelomonocytic leukemia * RAEB in transformation * RA or RARS must have at least one of the following: * Absolute neutrophil count less than 1,000/mm\^3 * Untransfused hemoglobin less than 8 g/dL * Platelet count less than 20,000/mm\^3 * Anemia * Thrombocytopenia requiring transfusion * High risk chromosomal abnormalities * Any stage of MDS allowed including: * Previously untreated MDS * Refractory MDS allowed if failure to achieve remission following prior intensive chemotherapy of at least 1 month ago * Relapsed, refractory, or untreated acute myeloid leukemia (AML) with the following: * WBC less than 30,000/mm\^3 * Stable for at least 2 weeks * Unlikely to require cytotoxic therapy during study * Untreated AML with poor risk factors for response to standard therapy including: * Greater than 60 years old * AML occurs in setting of antecedent hematologic disorder * High risk chromosomes (e.g., abnormalities of chromosome 5 or 7 or complex cytogenetic abnormalities) * Medical conditions that preclude cytotoxic chemotherapy as primary therapy * Refusal of cytotoxic chemotherapy allowed * No clinical evidence of CNS leukostasis or CNS leukemia PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Zubrod 0-2 Life expectancy: * Not specified Hematopoietic: * See Disease Characteristics * Hemoglobin at least 8 g/dL (transfusion allowed) Hepatic: * Bilirubin less than 2.0 mg/dL (unless due to hemolysis or Gilbert's disease) Renal: * Creatinine less than 2.0 mg/dL Cardiovascular: * No disseminated intravascular coagulation Pulmonary: * No pulmonary leukostasis Other: * No active infection * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception 2 weeks prior, during and 3 months after study PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 3 weeks since prior biologic therapy including colony stimulating factors and recovered Chemotherapy: * See Disease Characteristics * At least 3 weeks since prior chemotherapy and recovered Endocrine therapy: * At least 3 weeks since prior hormonal therapy and recovered Radiotherapy: * At least 3 weeks since prior radiotherapy and recovered Surgery: * Not specified