Compounds of the formula I in which R1, R2 and R4 have the meanings indicated in Claim 1, are inhibitors of Syk, and can be employed, inter alia, for the treatment of cancer, rheumatoid arthritis and / or systemic lupus本發明提供一種式I化合物其中R1、R2及R4具有申請專利範圍第1項中指示之含義,該等化合物係Syk之抑制劑,且尤其可用於治療癌症、類風濕性關節炎及/或全身性狼瘡。