Compounds of formula (I): wherein R1 is C1-6alkylamino, or C1-6alkoxy; R2 is a group having the structure: n is an integer having a value of 1 to 6; Het is a 6-membered saturated heterocycle containing one nitrogen atom wherein Het is attached to the —(CH2)n— moiety at any carbon atom of the heterocycle; R3 is hydrogen, C1-8alkyl, or C3-7cycloalkylC0-6alkyl; and salts thereof are inducers of human interferon. Compounds which induce human interferon may be useful in the treatment of various disorders, for example the treatment of allergic diseases and other inflammatory conditions for example allergic rhinitis and asthma, the treatment of infectious diseases and cancer, and may also be useful as vaccine adjuvants.