Thioglycerol derivatives

A compound of the invention is represented by the formula: wherein R1 and R2 are the same or different, an acyl group; R3, R4, R6 and R7 are the same or different, hydrogen or an alkyl group; R5 is hydrogen, an alkyl group or a hydroxyl group which may optionally be protected, or R4 and R5 are combined to form a chemical bond; X is a carbonyl group or a sulfonyl group; Y is an amino acid sequence consisting of 1 to 7 amino acid residues which may optionally be protected and having optionally an intervening -SO2NH-; n is an integer of 0 to 2, or a salt thereof. The compound or salt thereof of the present invention possesses immunoenhancing activity and platelet reduction recovery activity, and can be used as a prophylactic/therapeutic agent for leukocytopenia in cancer chemotherapy or radiotherapy, as an immunoenhancing agent in bone marrow transplantation therapy and the treatment of osteomyelodysplasia and aplastic anemia, and as a prophylactic/therapeutic agent for thrombocytopenia.