The present invention relates to a process for preparing methyl {4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-5-yl}methylcarbamate of the formula (I)and to a process for purifying the crude product of the compound of the formula (I) for use as pharmaceutically active compound, where, for purification, methyl {4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridi ne-3-yl]pyrimidin-5-yl}methylcarbamate sulphinyldimethane (1:1), i.e. a compound of the formula (II), is isolated as intermediate or is generated as intermediated in this purification process, if appropriate present in a mixture.本發明係關於一種製備式(I)之{4,6-二胺基-2-[1-(2-氟苯甲基)-1H-吡唑并[3,4-b]吡啶-3-基]嘧啶-5-基}甲基胺基甲酸甲酯之方法，並關於一種用於純化使用作為醫藥活性化合物之式(I)化合物之粗產物方法，其中為了純化，以中間物形式分離出{4,6-二胺基-2-[1-(2-氟苯甲基)-1H-吡唑并[3,4-b]吡啶-3-基]嘧啶-5-基}甲基胺基甲酸甲酯亞磺醯基二甲烷(1：1)，即式(II)化合物或在此純化製程中以中間物形式產生，若適當以混合物形式存在。
