This invention relates to certain unsaturated fatty acid derivatives of therapeutically active 1,3-dioxolane nucleoside analogues and to pharmaceutical formulations containing them. The said derivatives are referred to as “Compounds of formula (I)” herein. Compounds of formula (I) can be used in the treatment of a cancerous disease. Treatment of both solid tumours and haematological cancers such as leukaemias, lymphomas and multiple myelomas are included.