Abstract: The invention is directed to a compound according to the formula [1] wherein R1 and R2 are branched or straight groups having up to 17 atoms selected from carbon, nitrogen, oxygen and sulphur, n is 0 to and including 18, Y is sulphur or selene, X is S or 0 and R is —OH or an organic group comprising one or more peptides, one or more nucleic acids, one or more antibodies or combinations thereof. The invention is also directed to process for preparing said compound and the use of said compound as an adjuvant. The invention is also directed to a composition comprising said compound and the use of said composition, for example as a vaccine composition.