PURPOSE: To easily and economically obtain the subject compd. useful as an intermediate of an antileukemic agent by a specified method using a di(trialkylsilylamino)-trialkylsilylpurine as a starting material.

CONSTITUTION: First, a 2,6-di(trialkylsilylamino)-9-trialkylsilylpurine expressed by formula I (with the proviso that alkyl is a 1-4C alkyl) is reacted with 2,3,5-tri- O-benzyl-1-chloro-D-arabinofuranose expressed by formula II preferably at 80 to 85°C for 18 to 30 hours in 1,2-dichloroethane to obtain a 2,6-di(trialkylsilylamino)-9-(2,3,5-tri-O-benzyl-β-D-arabino-furanosyl)purine. Then the obtd. compd. is reacted with a 1-4C alkanol (preferably methanol) in the reaction liquid preferably at 50 to 60°C for 30 to 120 min to obtain the objective compd. expressed by formula III, which is then separated from the liquid.