RATIONALE: Drugs used in chemotherapy, such as treosulfan and fludarabine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving treosulfan and fludarabine together with a donor bone marrow transplant or a peripheral stem cell transplant may be an effective treatment for acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome.