##STR1## The present invention relates to compounds of formula (I), in which formula R stands for an alkyl group containing from 7 to 12 carbon atoms optionally substituted with a hydroxy group; and derivatives of the compounds of formula (I) in which one or more hydroxy groups have been transformed into --O-acyl or --O-glycosyl or phosphate ester groups, such masked groups being hydrolyzable in vivo, in pure form or in mixtures. The present compounds find use in both the human and veterinary practice in the treatment and prophylaxis of autoimmune diseases, including diabetes mellitus, hypertension, inflammatory diseases such as rheumatoid arthritis and asthma as well as diseases characterized by abnormal cell differentiation and/or cell proliferation, and/or imbalance in the immune system.