Compounds of formula (I):wherein: R1 is butoxy or methylbutoxy； R2 is a group having the structure:where n is an integer having a value of five； Het is a six-membered saturated heterocycle containing five carbon atoms and one nitrogen atom, wherein Het is attached to the —(CH2)n— moiety at the carbon 4 position of the heterocycle； and R3 is hydrogen； or pharmaceutically acceptable salts thereof； and their use as vaccine adjuvants and in the treatment of various disorders.
