Combination Chemotherapy With or Without Gemtuzumab Ozogamicin or Tipifarnib in Treating Patients With Acute Myeloid Leukemia or High-Risk Myelodysplastic Syndromes

DISEASE CHARACTERISTICS: * Diagnosis of 1 of the following: * Acute myeloid leukemia (AML) meeting the following criteria: * De novo or secondary AML * No acute promyelocytic leukemia * High-risk myelodysplastic syndromes (\> 10% marrow blasts; refractory anemia with excess blasts-2) * No blast transformation of chronic myeloid leukemia * Patients ≤ 60 years of age may be eligible provided they are considered unfit for clinical trial MRC-AMLI5 PATIENT CHARACTERISTICS: * Not pregnant or nursing * AST and ALT ≤ 2 times upper limit of normal (ULN) (for patients receiving gemtuzumab ozogamicin) * Bilirubin ≤ 2 times ULN (for patients receiving gemtuzumab ozogamicin) * Creatinine normal (for patients receiving clofarabine) * No other concurrent active malignancy except basal cell carcinoma PRIOR CONCURRENT THERAPY: * No prior cytotoxic chemotherapy for AML * Hydroxyurea or similar low-dose therapy to control WBC count prior to initiation of intensive therapy allowed * No concurrent enzyme anticonvulsants, including phenytoin, phenobarbital, primidone, carbamazepine, or oxcarbazepine (for patients receiving tipifarnib)