The present invention relates to compounds of formula (I) and (IV), and pharmaceutically acceptable salts, tautomers, stereoisomers thereof, which are inhibitors of histone deacetylase (HDAC). The compounds of the present invention are for use in the treatment of disorders that are ameliorated by inhibition of HDAC such as cancer and hemoglobinopathies like &bgr；-thalassemia or sickle cell anemia.
