A method for producing adenine compound (1): wherein m and n are independently an integer of 2 to 5, R1 is C1-6 alkyl group, R2 and R3 are the same or different, and hydrogen atom, or C1-6 alkyl group, or R2 and R3 are combined with an adjacent nitrogen atom to form pyrrolidine, morpholine, piperidine, piperazine, etc., and R4 is C1-3 alkyl group, which comprises a step of reacting compound (2): and compound (3): in the presence of a boron-containing reducing agent.